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Chemical and Mechanical Fallow Weed Control Methods in Florida Vegetable Crops

Permanent Link: http://ufdc.ufl.edu/UFE0024486/00001

Material Information

Title: Chemical and Mechanical Fallow Weed Control Methods in Florida Vegetable Crops
Physical Description: 1 online resource (283 p.)
Language: english
Creator: Mcavoy, Theodore
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: amaranth, beans, cabbage, chemical, crabgrass, cultivation, fallow, glyphosate, halosulfuron, herbicides, mechanical, metolachlor, morningglory, nutsedge, oxyfluorfen, paraquat, peppers, pusley, redweed, tillage, trifloxysulfuron, vegetable, weed
Horticultural Science -- Dissertations, Academic -- UF
Genre: Horticultural Science thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Field experiments were conducted in Live Oak and Citra, Florida during the summers of 2006 and 2007 to determine the efficacy of fallow weed control methods on controlling weeds during the fallow season, controlling weeds during the growing season, and their influence on crop yields. Furthermore, several pre-plant herbicides were used to determine weed control efficacy for certain weeds and their effect on crop yield, when used in conjunction with fallow weed control methods. Fallow weed control treatments included an untreated check, a cultivated check, post-emergent herbicides, pre-emergent herbicides, systemic herbicides, contact herbicides, combinations of herbicides with cultivation and combinations of herbicides with each other. The broad spectrum herbicides used for fallow weed control were glyphosate, paraquat, glyphosate tank-mixed with halosulfuron, glyphosate mixed with trifloxysulfuron, glyphosate tank-mixed with s-metolachlor, paraquat tank-mixed with trifloxysulfuron and paraquat tank-mixed with s-metolachlor. The pre-plant herbicides used were oxyfluorfen and s-metolachlor for cabbage. EPTC, s-metolachlor, and pendimethalin were used for snap beans. In peppers, EPTC, s-metolachlor, and clomazone were applied under the plastic. Leaving the field idle during the fallow period provided unacceptable weed control during the fallow and crop. In addition, the untreated check resulted in the lowest cabbage yields. Cultivation controlled emerged broadleaf and grassy weeds during the fallow period, but did not provide pre-emergent or substantial long term weed control during the crop. Cultivation increased purple nutsedge compared to the untreated control in Live Oak. In Citra, cultivation decreased nutsedge significantly compared to the untreated control. However, cultivation did not reduce purple nutsedge to an acceptable level for crop production. Glyphosate and paraquat both provided post-emergent control of all weeds present; however, no pre-emergent activity was provided. S-metolachlor provided pre-emergent activity, increased total control of yellow nutsedge, crabgrass, and various broadleaf weeds during the fallow period. Halosulfuron did not improve weed control or yields beyond that provided by glyphosate alone. Trifloxysulfuron increased purple and yellow nutsedge control when added to glyphosate or paraquat. In addition, trifloxysulfuron provided excellent pre-emergent and long term broadleaf weed control. However, trifloxysulfuron negatively impacted cabbage vigor, and yield.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Theodore Mcavoy.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Stall, William M.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024486:00001

Permanent Link: http://ufdc.ufl.edu/UFE0024486/00001

Material Information

Title: Chemical and Mechanical Fallow Weed Control Methods in Florida Vegetable Crops
Physical Description: 1 online resource (283 p.)
Language: english
Creator: Mcavoy, Theodore
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: amaranth, beans, cabbage, chemical, crabgrass, cultivation, fallow, glyphosate, halosulfuron, herbicides, mechanical, metolachlor, morningglory, nutsedge, oxyfluorfen, paraquat, peppers, pusley, redweed, tillage, trifloxysulfuron, vegetable, weed
Horticultural Science -- Dissertations, Academic -- UF
Genre: Horticultural Science thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Field experiments were conducted in Live Oak and Citra, Florida during the summers of 2006 and 2007 to determine the efficacy of fallow weed control methods on controlling weeds during the fallow season, controlling weeds during the growing season, and their influence on crop yields. Furthermore, several pre-plant herbicides were used to determine weed control efficacy for certain weeds and their effect on crop yield, when used in conjunction with fallow weed control methods. Fallow weed control treatments included an untreated check, a cultivated check, post-emergent herbicides, pre-emergent herbicides, systemic herbicides, contact herbicides, combinations of herbicides with cultivation and combinations of herbicides with each other. The broad spectrum herbicides used for fallow weed control were glyphosate, paraquat, glyphosate tank-mixed with halosulfuron, glyphosate mixed with trifloxysulfuron, glyphosate tank-mixed with s-metolachlor, paraquat tank-mixed with trifloxysulfuron and paraquat tank-mixed with s-metolachlor. The pre-plant herbicides used were oxyfluorfen and s-metolachlor for cabbage. EPTC, s-metolachlor, and pendimethalin were used for snap beans. In peppers, EPTC, s-metolachlor, and clomazone were applied under the plastic. Leaving the field idle during the fallow period provided unacceptable weed control during the fallow and crop. In addition, the untreated check resulted in the lowest cabbage yields. Cultivation controlled emerged broadleaf and grassy weeds during the fallow period, but did not provide pre-emergent or substantial long term weed control during the crop. Cultivation increased purple nutsedge compared to the untreated control in Live Oak. In Citra, cultivation decreased nutsedge significantly compared to the untreated control. However, cultivation did not reduce purple nutsedge to an acceptable level for crop production. Glyphosate and paraquat both provided post-emergent control of all weeds present; however, no pre-emergent activity was provided. S-metolachlor provided pre-emergent activity, increased total control of yellow nutsedge, crabgrass, and various broadleaf weeds during the fallow period. Halosulfuron did not improve weed control or yields beyond that provided by glyphosate alone. Trifloxysulfuron increased purple and yellow nutsedge control when added to glyphosate or paraquat. In addition, trifloxysulfuron provided excellent pre-emergent and long term broadleaf weed control. However, trifloxysulfuron negatively impacted cabbage vigor, and yield.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Theodore Mcavoy.
Thesis: Thesis (M.S.)--University of Florida, 2009.
Local: Adviser: Stall, William M.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024486:00001


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1 CHEMICAL AND MECHANICAL FALLOW WE ED CONTROL METHODS IN FLORIDA VEGETABLE CROPS By THEODORE PORTER MCAVOY A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2009

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2 2009 Theodore Porter McAvoy

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3 To my Parents

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4 ACKNOWLEDGMENTS I would like to acknowledge ever yone that has helped m e in my journey and has supported me in my endeavors. I want to start by thanki ng my parents for instil ling goals, pushing me to succeed, and nurturing my dreams. I certainly woul d not be where I am at today if it were not for my parents persistence and compassion. Thank you mom and dad. I would like to acknowledge Dr. Kent Cushman for inspiring me to further my education by pursuing my masters degree and for steering me to work in weed science with Dr. Stall. I owe Dr. Cushman a great deal of gratitude and will always remember him for changing my life for the better. Thank you Dr. Cushman. Dr. Bill Stall has been a great advisor that is knowledgeable, approachable, flexible, and a great friend. He is a pioneer in Florida weed sc ience and has invaluable experience. On top of that I would like to thank him for sharing his friendship, offeri ng advice, and providing me (and Josh) with stories about the good old days. Ma y you enjoy your retirement which you have earned and undoubtedly deserve. Thanks for being patient and waiting for me to finally finish. Thank you Dr. Stall. I would like to thank my committee members, Dr. MacDonald and Dr. Santos. Dr. Greg MacDonald you were one of my favorite teachers in graduate school, and among the best weed scientists at the University of Florida. I am honored that you were on my committee. Thank you Dr. MacDonald. Dr. Bielinski Santos you are among the best horticulturalists in IFAS. In addition, you are an asset because of your exte nsive knowledge of purpl e nutsedge, herbicides, and statistics. Thank you Dr. Santos. I would like to thank a ll of the field staff at Citra a nd Live Oak, especially John Moses Morris. John I would like to thank you for help ing me mix herbicides, collect data, and harvest crops in my field experiment. Also, I want to thank you for being my friend, sharing stories

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5 about the navy, inviting me into your home and h eart. Thank you John. I could not have carried out my field experiments at Live Oak if it we re not for Randi Randell, Jerry, Lani, Bug, and others. In Citra, I would like to thank Buck, David Studstill, Darrel Thomas, and all the Citra farm staff. I would like to thank Sadie in Im mokalee for helping me c ount weeds in the middle of the summer accompanied by blistering heat, sugar sand, and afternoon thunder storms. Thanks you guys. I would like to thank a ll the graduate students that help ed me with my field research, statistics, excel, and writing. I could not have ach ieved this great feat wi thout Josh Adkins, Cami Esmel, Aparna Gazula, Oren Warren, Manish Bh an, and Celeste Gilbert. Thank you everyone for your help and support. In addition to your p hysical help I would lik e to thank you for the mental support that you provided. Thank you everyone. I would like to thank professors that were not on my committee that helped me along the way. Thank you Dr. Bala Saba, Dr. Dan Cantliffe, Dr. Sargent, and Dr. Carlene Chase. I would like to thank all the staff and f aculty in the horticulture departme nt that has provided assistance in my years in Gainesville. Thank you Melisa Webb, Curtis Smyder, Carolyn Miller, Tammy King, Donna Dyer, Brenda Harris, Debbie Fields, and Bob Morris. I would like to thank Mark Elliott from the plant pathology department for his advice on writing a thesis. I would like to thank Duda a nd L&M Farms for allowing me to conduct research on their farms. I want to thank Syngenta and Gowan for donating herbicides for my project. Lastly, I would like to thank Transgro and Speedling for pr oviding transplants for my experiment. Thank you to everyone that invested tim e and money into my research.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4LIST OF FIGURES.......................................................................................................................11ABSTRACT...................................................................................................................................19CHAPTER 1 LITERATURE REVIEW.......................................................................................................21Introduction................................................................................................................... ..........21Fallowing and Fallow Weed Control..............................................................................21Reasons for Fallowing..................................................................................................... 21Weeds: Explanations and Problems................................................................................ 22Sexual and Asexual Reproduction................................................................................... 23Characteristics of Weeds................................................................................................. 23Crop-Weed Competition................................................................................................. 25Critical Weed-Free Period...............................................................................................26Host plants for pests........................................................................................................27Common and Troublesome Weed s in Vegetable Crops.................................................. 28Cyperus rotundus L..................................................................................................28Eleusine indica (L.) Gaertn......................................................................................30Portulaca oleracea L...............................................................................................30Digitaria sanguinalis (L.) Scop............................................................................... 30Amaranthus hybridus ...............................................................................................31Cyperus esculentus L...............................................................................................31Negative Impact of Weeds in Various Crops.................................................................. 31Methyl Bromide Alternatives..........................................................................................33Tillage........................................................................................................................ ......38Seed Bank (Survival and Dormancy).............................................................................. 39Stale Seed Bed................................................................................................................. 40Herbicides Labeled for Fallowing -Post Emergence Applications................................. 41Halosulfuron-methyl................................................................................................41Glyphosate................................................................................................................44Paraquat....................................................................................................................48Trifloxysulfuron....................................................................................................... 49Pre-emergence Herbicides............................................................................................... 51EPTC........................................................................................................................51Halosulfuron-methyl................................................................................................53Pre-plant herbicides labeled for vegetable crops............................................................. 54S-metolachlor...........................................................................................................54Clomazone................................................................................................................ 56Pendimethalin........................................................................................................... 57

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7 Oxyfluorfen..............................................................................................................58General factors effecting herbicide efficacy.................................................................... 60Herbicide activity on crops..............................................................................................62Previous fallow work.......................................................................................................622 FALLOW EXPERIMENT LIVE OAK, FL LOCATION................................................... 66Materials and Methods...........................................................................................................66Year 1 Fallow................................................................................................................67Year 1 Crop...................................................................................................................67Year 2 Fallow................................................................................................................69Year 2 Crop...................................................................................................................71Statistical Analysis.......................................................................................................... 73Results and Discussion......................................................................................................... ..73Fallow Period...................................................................................................................73Purple nutsedge fallow.............................................................................................73Yellow nutsedge.......................................................................................................75Florida pusley fallow................................................................................................75Crabgrass fallow.......................................................................................................76Hairy indigo fallow..................................................................................................78Browntop millet fallow............................................................................................ 78Smallflower morningglory (data not shown)........................................................... 79Carpetweed fallow.................................................................................................... 80Redweed fallow (data not shown)............................................................................80Other minor weeds (data not shown).......................................................................81Crop Data.........................................................................................................................81Purple nutsedge in peppers year 1......................................................................... 81Weeds in pepper rows year 1................................................................................. 82Weeds in pepper row middle year 1...................................................................... 83Pepper heights year 1............................................................................................. 84Weeds in beans year 1............................................................................................ 84Crop yields year 1 (data not shown)...................................................................... 87Purple nutsedge within the pepper row year 2....................................................... 87Cabbage weeds year 2............................................................................................ 89Bean weeds year 2................................................................................................. 93Pepper and bean dry weights year 2 (dat a not shown)........................................... 96Cabbage yield year 2..............................................................................................97Conclusions.............................................................................................................................98Purple Nutsedge Control.................................................................................................98Yellow Nutsedge Control................................................................................................98Florida Pusley Control.....................................................................................................99Large Crabgrass Control................................................................................................100Hairy Indigo Control.....................................................................................................100Browntop Millet Control...............................................................................................101Smallflower Morningglory Control............................................................................... 101Carpetweed Control....................................................................................................... 101Cutleaf Evening Primrose Control................................................................................101

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8 Cabbage Yield...............................................................................................................1023 FALLOW EXPERIMENT CITRA, FL LOCATION....................................................... 151Objective...............................................................................................................................151Materials and Methods.........................................................................................................151Fallow Measurements.................................................................................................... 152Crop 1............................................................................................................................153Crop 2............................................................................................................................153Post Cabbage Harvest Weed Control............................................................................ 154Statistical Analysis........................................................................................................ 154Results and Discussion......................................................................................................... 154Fallow Period (Sedges)..................................................................................................154Effect of different fallow treatments on purple nutsedge control year 1.............154Effect of different fallow treatments on purple nutsedge control year 2.............157Purple nutsedge counts year 2..............................................................................159Yellow fallow control ratings year 2...................................................................159Yellow nutsedge counts year 2............................................................................160Fallow Period Grasses................................................................................................. 160Crabgrass fallow ratings year 1............................................................................ 160Crabgrass fallow ratings year 2............................................................................ 161Crabgrass counts year 2....................................................................................... 163Goosegrass control ra tings year 2........................................................................ 165Goosegrass counts year 2..................................................................................... 166Corn fallow ratings year 2....................................................................................166Crowfootgrass control ratings year 2................................................................... 166Fallow Broadleaves.....................................................................................................167Amaranth fallow control ratings year 1............................................................... 167Amaranth fallow control ratings year 2............................................................... 168Amaranth counts year 2....................................................................................... 169Purslane fallow ratings year 1.............................................................................. 170Purslane fallow ratings year 2.............................................................................. 172Purslane counts year 2......................................................................................... 172Florida pusley control ratings year 1................................................................... 173Florida pusley control ratings year 2................................................................... 173Florida pusley counts year 2................................................................................ 174Cutleaf evening primrose control ratings year1................................................... 175Cutleaf ground cherry cont rol ratings year 2....................................................... 175Cutleaf ground cherry counts year 2.................................................................... 176Carpetweed fallow control ratings year 2............................................................ 177Carpetweed counts year 2.................................................................................... 177Redweed control ratings year 2............................................................................ 178Cabbage Vigor Ratings and Weed Control Ratings during the Crop............................ 178Purple Nutsedge.............................................................................................................178Fallow treatment effect...........................................................................................178Pre-plant treatment effect....................................................................................... 180Yellow Nutsedge Control in Cabbage........................................................................... 180

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9 Crabgrass Control in Cabbage....................................................................................... 181Fallow treatment effect...........................................................................................181Pre-plant treatment effect....................................................................................... 182Cutleaf Evening Primrose.............................................................................................. 182Fallow treatment effect...........................................................................................182Pre-plant treatment effect....................................................................................... 183Purslane Control in Cabbage......................................................................................... 183Fallow treatment effect...........................................................................................183Pre-plant treatment effect....................................................................................... 184Cabbage Weed Counts..................................................................................................184Cabbage Vigor...............................................................................................................185Cabbage Yield Year 2................................................................................................. 186Cabbage Number...........................................................................................................186Total Cabbage Weight................................................................................................... 187Average Cabbage Weight.............................................................................................. 188Total Cabbage Weight................................................................................................... 189Average Cabbage Weight.............................................................................................. 189Weeds after Cabbage Harvest....................................................................................... 190Purple nutsedge post cabbage harvest....................................................................190Crabgrass post cabbage harvest.............................................................................. 191Pusley post cabbage harvest................................................................................... 191Purslane post cabbage harvest................................................................................ 192Conclusions...........................................................................................................................193Fallow Treatments......................................................................................................... 193Untreated fallow.....................................................................................................193Cultivation..............................................................................................................193Glyphosate..............................................................................................................194Glyphosate plus s-metolachlor............................................................................... 194Glyphosate plus trifloxysulfuron............................................................................ 195Paraquat..................................................................................................................196Paraquat plus s-metolachlor................................................................................... 197Paraquat plus trifloxysulfuron................................................................................197Pre-plant Herbicide Treatments..................................................................................... 198Oxyfluorfen............................................................................................................198S-metolachlor.........................................................................................................1984 CONCLUSIONS LIVE OAK AND CITRA SUMMARY............................................... 268Untreated Fallow Effect on Weeds....................................................................................... 268Live Oak........................................................................................................................268Citra...............................................................................................................................268Effect of Fallow Cultivation on Weeds (R egardless of Herbicides) Live Oak.................. 269Fallow Cultivation Effect on Weeds.....................................................................................269Effect of Fallow Herbicides on Weeds (R egardless of Cultiva tion) Live Oak.................. 270Fallow Herbicide Effects on Weeds..................................................................................... 270Effect of Fallow Treatments on Weeds within Peppers....................................................... 272Untreated Fallow Effect on Peppers Live Oak........................................................... 272

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10 Fallow Cultivation Effect on Peppers Live Oak......................................................... 272Effect of Fallow Herbicides on Bell Pepper (Regardless of Cultivation) Live Oak... 273Fallow Herbicide Effect on Peppers Live Oak........................................................... 273Effects of Fallow Treatments on Snap Beans.......................................................................273Effect of Fallow Cultivation in Snap Bean s (Regardless of Herbicides) Live Oak.... 273Effect of Fallow Herbicides on Snap Bean s (Regardless of Tillage) Live Oak.......... 273Effect of Fallow Treatments on Weeds within Cabbage...................................................... 274Untreated Fallow Effect on Cabbage............................................................................274Fallow Cultivation Effect on Cabbage.......................................................................... 274Fallow Herbicide Effect on Cabbage Live Oak.......................................................... 275Fallow Herbicide Treatment Effect on Weeds during Cabbage Crop Citra............... 275Fallow Treatment Effect on Cabba ge Vigor and Yield Citra..................................... 275Effect of Pre-plant Herbicides on Cabbage..........................................................................276LIST OF REFERENCES.............................................................................................................278BIOGRAPHICAL SKETCH.......................................................................................................283

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11 LIST OF FIGURES Figure page 1-1 Experimental design of Live Oak, FL experim ent during the first year.......................... 103 1-2 Purple nutsedge counts during the su mmer 2006 and 2007 fallow period in Live Oak, Fl ......................................................................................................................................104 1-3 Effect of herbicides on purple nu tsedge counts during the summ er 2006 and 2007 fallow period in Live Oak, Fl...........................................................................................105 1-4 Effect of treatments on purple nuts edge counts during the summ er 2007 fallow period in Live Oak, Fl...................................................................................................... 106 1-5 Yellow nutsedge counts during the su mm er 2006 and 2007 fallow period in Live Oak, Fl..............................................................................................................................107 1-6 Effect of treatment by date interacti on on yellow nutsedge counts during the summ er 2006 and 2007 fallow period in Live Oak, Fl.................................................................. 108 1-7 Florida pusley counts during the summ er 2006 and 2007 fallow period in Live Oak, Fl ......................................................................................................................................109 1-8 Effect of herbicides on Florida pusley counts during the sum mer 2006 and 2007 fallow period.................................................................................................................. ..110 1-9 Effect of cultivation on Florida pusley counts during the sum mer 2006 and 2007 fallow period.................................................................................................................. ..111 1-10 Large crabgrass counts during the su mm er 2006 and 2007 fallow period in Live Oak, Fl......................................................................................................................................112 1-11 Interaction effect of treat m ent and date on large crabgrass counts during the summer 2006 and 2007 fallow period in Live Oak, Fl.................................................................. 113 1-12 Hairy Indigo counts during the summer 2006 and 2007 fallow period in Live Oak, Fl .. 114 1-13 Effect of herbicides on hairy indi go counts during the summ er 2006 and 2007 fallow period...............................................................................................................................115 1-14 Browntop Millet counts during the summer 2006 and 2007 fallow period in Live Oak, Fl..............................................................................................................................116 1-15 Effect of treatment on browntop m illet counts during the summ er 2006 and 2007 fallow period in Live Oak, Fl...........................................................................................117 1-16 Effect of herbicides on browntop millet counts during the summer 2006 and 2007 fallow period .................................................................................................................. ..118

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12 1-17 Carpetweed counts during the summer 2006 and 2007 fallow period in Live Oak, Fl ... 119 1-18 Interaction effect of treatment and da te on carpetweed counts during the summ er 2006 and 2007 fallow period in Live Oak, Fl.................................................................. 120 1-19 Purple nutsedge counts per 30 linear bed feet of row within a bell pepper crop during the spring of 2007 in Live Oak, Fl ...................................................................................121 1-20 Effect of herbicides on purple nutsedge counts per 30 linear bed feet within a bell pepper crop during the spring of 2007 in Live Oak, Fl ................................................... 122 1-21 Effect of herbicides for Florida pusle y counts located in the planting holes per 30 linear bed feet within a bell pepper crop during the spri ng of 2007 in Live Oak, Fl ....... 123 1-22 Herbicide main effect for crabgrass count s per 30 LBF within the rows of a pepper crop during the spring of 2007 in Live Oak, Fl ............................................................... 124 1-23 Cultivation main effect for crabgrass count s per 3 0 LBF within the rows of a pepper crop during the spring of 2007 in Live Oak, Fl............................................................... 125 1-24 Herbicide main effect for Florida pusley counts per m2 located within the row middle of a pepper crop during the sp ring of 2007 in Live Oak, Fl............................................126 1-25 Herbicide main effect for large crabgrass counts per m2 located within the row middle of a bell pepper crop during the spring of 2007 in Live Oak, Fl.........................127 1-26 Herbicide main effect for the average of six bell pepper heig hts in cm during the spring of 2007 in Live Oak, Fl.........................................................................................128 1-27 Herbicide main effect for the overall percentage of ground cover for all weed species com bined in a snap bean crop during the spring of 2007 in Live Oak, Fl.......................129 1-28 Herbicide main effect for purple nutsedge counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl............................................................... 130 1-29 Herbicide main effect for Florida pusley counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl.......................................................................131 1-30 Herbicide main effect for large crabgrass counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl............................................................... 132 1-31 Cultivation main effect for large crabgrass counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl............................................................... 133 1-32 Purple nutsedge counts per 30 linear bed feet of row within a bell pepper crop during the fall of 2007 in Live Oak, Fl ........................................................................................ 134 1-33 Effect of herbicides on purple nutsedge counts per 30 linear bed feet within a bell pepper crop during the fall of 2007 in Live Oak, Fl ........................................................ 135

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13 1-34 Effect of fallow treatments on the cont rol of purple nutsedge in the rows of a cabbage crop during the fall of 2007 in Live Oak, Fl ...................................................... 136 1-35 Pre plant herbicide main effect for the control of sm all flower morningglory in the rows of a cabbage crop during th e fall of 2007 in Live Oak, Fl......................................137 1-36 Interaction effect of cultivation and pre plant herbicides on th e control of Florida pusley in the rows of a cabbage crop duri ng the fall of 2007 in Live Oak, Fl.................138 1-37 Interaction effect of cultivation and pr e plant herbicides on the control of large crabgrass in the rows of a cabbage cr op during the fall of 2007 in Live Oak, Fl ............139 1-38 Interaction effect of fa llow herbicides and pre plant herbicides on the control of cutleaf evening prim rose in the rows of a cabbage crop during the fall of 2007 in Live Oak, Fl.....................................................................................................................140 1-39 Main effect of pre plant herbicides on the control of large crabgrass in the rows of snap beans during the fall of 2007 in Live Oak, Fl ..........................................................141 1-40 Main effect of pre plant herbicides on the control of cutleaf evening primrose in the rows of snap beans during the fall of 2007 in Live Oak, Fl ............................................. 142 1-41 Main effect of pre plant herbicides on the control of s mallflower morningglory in the rows of snap beans during the fall of 2007 in Live Oak, Fl.............................................143 1-42 Main effect of fallow herbicides on the control of sm allflowe r morningglory in the rows of snap beans during the fall of 2007 in Live Oak, Fl.............................................144 1-43 Interaction effect of fa llow herbicides and pre plant herbicides on the control of Florida pusley in the rows of snap bean s during the fall of 2007 in Live Oak, Fl ........... 145 1-44 Interaction effect of cultivation and pre plant herbicides on th e control of Florida pusley in the rows of snap beans during the fall of 2007 in Live Oak, Fl ....................... 146 1-45 Main effect of fallow herbicides on the control of purple nutse dge in the rows of snap beans during the fall of 2007 in Live Oak, Fl ..........................................................147 1-46 Main effect of pre plant herbicides on the num ber of cabbage per plot (15 LBF) during the winter of 2008 in Live Oak, Fl.......................................................................148 1-47 Main effect of pre plant herbicides on the to tal cabbage weight during the winter of 2008 in Live Oak, Fl........................................................................................................149 1-48 Main effect of pre plant herbicides on the average cabbage w eight during the winter of 2008 in Live Oak, Fl....................................................................................................150 2-1 Effect of different fallow treatments on th e control of purple nutsedge during the first fallow season in Citra, Fl .................................................................................................199

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14 2-2 Effect of different fallow treatments on th e control of purple nutsedge during the first fallow season in Citra, Fl .................................................................................................200 2-3 Effect of different fallow treatments on the control of purple nutsedge during the second fallow season in Citra, Fl ..................................................................................... 201 2-4 Effect of different fallow treatments on the control of purple nutsedge during the second fallow season in Citra, Fl ..................................................................................... 202 2-5 Effect of different fallow treatments on the population density of purple nutsedge during the second fallow season in Citra, Fl .................................................................... 203 2-6 Effect of different fallow treatments on the population density of purple nutsedge during the second fallow season in Citra, Fl .................................................................... 204 2-7 Effect of different fallow treatments on the control of yello w nutsedge during the second fallow season in Citra, Fl ..................................................................................... 205 2-8 Effect of different fallow treatments on the control of yello w nutsedge during the second fallow season in Citra, Fl ..................................................................................... 206 2-9 Effect of different fallow treatments on the population density of yellow nutsedge during the second fallow season in Citra, Fl.................................................................... 207 2-10 Effect of different fallow treatments on the population density of yellow nutsedge during the second fallow season in Citra, Fl.................................................................... 208 2-11 Effect of different fallow treatments on th e con trol of large crabgrass during the first fallow season in Citra, Fl.................................................................................................209 2-12 Effect of different fallow treatments on the con trol of large crabgrass during the second fallow season in Citra, Fl..................................................................................... 210 2-13 Effect of different fallow treatments on the con trol of large crabgrass during the second fallow season in Citra, Fl..................................................................................... 211 2-14 Effect of different fallow treatments on the population density of large crabgrass during the second fallow season in Citra, Fl .................................................................... 212 2-15 Effect of different fallow treatments on the population density of large crabgrass during the second fallow season in Citra, Fl .................................................................... 213 2-16 Effect of different fallow treatments on the control of goosegrass during the first fallow season in Citra, Fl .................................................................................................214 2-17 Effect of different fallow treatments on the control of goosegrass during the first fallow season in Citra, Fl .................................................................................................215

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15 2-18 Effect of different fallow treatments on the control of goosegrass during the second fallow season in Citra, Fl .................................................................................................216 2-19 Effect of different fallow treatments on the population density of goosegrass during the second f allow season in Citra, Fl............................................................................... 217 2-20 Effect of different fallow treatments on the control of volunteer corn plants during the second f allow season in Citra, Fl............................................................................... 218 2-21 Effect of different fallow treatments on the control of volunteer corn plants during the second f allow season in Citra, Fl............................................................................... 219 2-22 Effect of different fallow treatments on the control of crowfootgrass plants during the second f allow season in Citra, Fl............................................................................... 220 2-23 Effect of different fallow treatments on the con trol of amaranth during the first fallow season in Citra, Fl.................................................................................................221 2-24 Effect of different fallow treatments on the con trol of amaranth during the first fallow season in Citra, Fl.................................................................................................222 2-25 Effect of different fallow treatments on the con trol of amaranth plants during the second fallow season in Citra, Fl..................................................................................... 223 2-26 Effect of different fallow treatments on the con trol of amaranth plants during the second fallow season in Citra, Fl..................................................................................... 224 2-27 Effect of different fallow treatments on the population density of am aranth during the second fallow season in Citra, Fl............................................................................... 225 2-28 Effect of different fallow treatments on the population density of am aranth during the second fallow season in Citra, Fl............................................................................... 226 2-29 Effect of different fallow treatments on the control of common purslane during the first fallow season in Citra, Fl ..........................................................................................227 2-30 Effect of different fallow treatments on the control of common purslane during the first fallow season in Citra, Fl ..........................................................................................228 2-31 Effect of different fallow treatments on the control of purslane plants during the second fallow season in Citra, Fl ..................................................................................... 229 2-32 Effect of different fallow treatments on the control of purslane plants during the second fallow season in Citra, Fl ..................................................................................... 230 2-33 Effect of different fallow treatments on the population density of purslane during the second fallow season in Citra, Fl ..................................................................................... 231

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16 2-34 Effect of different fallow treatments on the population density of purslane during the second fallow season in Citra, Fl ..................................................................................... 232 2-35 Effect of different fallow treatments on th e control of Florida pusley during the first fallow season in Citra, Fl .................................................................................................233 2-36 Effect of different fallow treatments on the control of Florida pusley plants during the second f allow season in Citra, Fl............................................................................... 234 2-37 Effect of different fallow treatments on the control of Florida pusley plants during the second f allow season in Citra, Fl............................................................................... 235 2-38 Effect of different fallow treatments on the population density of Florida pusley during the second fallow season in Citra, Fl .................................................................... 236 2-39 Effect of different fallow treatments on the con trol of cutleaf evening primrose during the first fallow season in Citra, Fl........................................................................237 2-40 Effect of different fallow treatments on the control of cutleaf ground cherry plants during the second fallow season in Citra, Fl .................................................................... 238 2-41 Effect of different fallow treatments on the control of cutleaf ground cherry plants during the second fallow season in Citra, Fl .................................................................... 239 2-42 Effect of different fallow treatments on the population density of cutleaf ground cherry during the second fallow season in Citra, Fl ......................................................... 240 2-43 Effect of different fallow treatments on the population density of cutleaf ground cherry during the second fa llow season in Citra, Fl......................................................... 241 2-44 Effect of different fallow treatments on the con trol of carpetw eed plants during the second fallow season in Citra, Fl..................................................................................... 242 2-45 Effect of different fallow treatments on the con trol of carpetw eed plants during the second fallow season in Citra, Fl..................................................................................... 243 2-46 Effect of different fallow treatments on the population density of carpetweed during the second f allow season in Citra, Fl............................................................................... 244 2-47 Effect of different fallow treatments on the population density of carpetweed during the second f allow season in Citra, Fl............................................................................... 245 2-48 Effect of different fallow treatments on the control of redweed plants during the second fallow season in Citra, Fl ..................................................................................... 246 2-49 Effect of different fallow treatments on the control of purple nutsedge plants during the second crop season (ca bbage) in Citra, Fl.................................................................. 247

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17 2-50 Effect of different preplant herb icide treatments on the control of purple nutsedge plants during the second crop season in Citra, Fl............................................................248 2-51 Effect of different fallow treatments on th e control of yellow nutsedge plants during the second crop season in Citra, Fl .................................................................................. 249 2-52 Effect of different fallow treatments on the con trol of crabgrass plants during the second crop season in Citra, Fl........................................................................................ 250 2-53 Effect of different pre-pl ant herb icide treatments on the control of crabgrass plants during the second crop season in Citra, Fl.......................................................................251 2-54 Effect of different pre-pl ant herb icide treatments on the control of cutleaf evening primrose plants during the sec ond crop season in Citra, Fl............................................. 252 2-55 Effect of different fallow treatments on the control of purslane plants during the second crop season in Citra, Fl ........................................................................................ 253 2-56 Effect of different pre-pl ant herb icide treatments on th e control of purslane plants during the second crop season in Citra, Fl.......................................................................254 2-57 Effect of different fallow treatments on the population density of purple nutsedge plants during the second crop season in Citra, Fl ............................................................255 2-58 Effect of different preplant herbicide treatm ents on the population density of yellow nutsedge plants during the sec ond crop season in Citra, Fl............................................. 256 2-59 Effect of different preplant herbicide treatm ents on the population density of large crabgrass plants during the second crop season in Citra, Fl............................................ 257 2-60 Effect of different fallow treatments on cabbage vigor during the second crop season in Citra, Fl ........................................................................................................................258 2-61 Effect of different fallow treatments on cabbage stand establishm ent during the second crop season in Citra, Fl........................................................................................ 259 2-62 Effect of different fallow treatments on total cabbage weight per plot (15 LBF of row) during the second cr op season in Citra, Fl .............................................................. 260 2-63 Effect of different fallow treatments on average cabbage weight during the second crop season in Citra, Fl .................................................................................................... 261 2-64 Effect of different pre-pl ant herb icide treatments on tota l cabbage weight per plot (15 LBF of row) during the sec ond crop season in Citra, Fl..................................................262 2-65 Effect of different pre-pl ant herb icide treatments on aver age cabbage weight per plot (15 LBF of row) during the second crop season in Citra, Fl...........................................263

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18 2-66 Effect of different summer fallow trea tm ents on the long term control of purple nutsedge after the harvest of the second crop in Citra, Fl................................................ 264 2-67 Effect of different summer fallow trea tm ents on the long term control of large crabgrass after the harvest of the second crop in Citra, Fl............................................... 265 2-68 Effect of different summer fallow treatm ents on the long term control of Florida pusley after the harv est of the second crop in Citra, Fl ................................................... 266 2-69 Effect of different summer fallow trea tm ents on the long term control of common purslane after the harvest of the second crop in Citra, Fl................................................ 267

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19 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science CHEMICAL AND MECHANICAL FALLOW WE ED CONTROL METHODS IN FLORIDA VEGETABLE CROPS By Theodore Porter McAvoy May 2009 Chair: William M. Stall Major: Horticultural Sciences Field experiments were conducted in Live Oak and Citra, Florida during the summers of 2006 and 2007 to determine the efficacy of fallo w weed control methods on controlling weeds during the fallow season, contro lling weeds during the growing season, and their influence on crop yields. Furthermore, several pre-plant herb icides were used to determine weed control efficacy for certain weeds and their effect on crop yield, when used in conjunction with fallow weed control methods. Fallow weed control treatm ents included an untreated check, a cultivated check, post-emergent herbicides, pre-emergent herbicides, systemic herbicides, contact herbicides, combinations of herbicides with cul tivation and combinations of herbicides with each other. The broad spectrum herbicides used fo r fallow weed control were glyphosate, paraquat, glyphosate tank-mixed with halosulfuron, glyphosat e mixed with trifl oxysulfuron, glyphosate tank-mixed with s-metolachlor, paraquat tank-m ixed with trifloxysulfuron and paraquat tankmixed with s-metolachlor. The pre-plant herbic ides used were oxyfluorfen and s-metolachlor for cabbage. EPTC, s-metolachlor, and pendimethalin we re used for snap beans. In peppers, EPTC, s-metolachlor, and clomazone were applied under the plastic. Leaving the field idle during the fallow period provided unac ceptable weed control during the fallow and crop. In addition, the untreated ch eck resulted in the lowest cabbage yields.

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20 Cultivation controlled emerged broadleaf and gra ssy weeds during the fallow period, but did not provide pre-emergent or substantial long term weed control during the crop. Cultivation increased purple nutsedge compared to the untrea ted control in Live Oak. In Citra, cultivation decreased nutsedge significantly compared to the untreated control. However, cultivation did not reduce purple nutsedge to an acceptable level for crop production. Glyphosate and paraquat both provided post-emergent control of all weeds present; however, no pre-emergent activity was provided. S-metolachlor provided pre-emergent activity, increased total control of yellow nutsedge, crabgrass, and various broadleaf weeds during the fallow period. Halosulfuron did not improve weed control or yields beyond that provided by glyphosate al one. Trifloxysulfuron increased purple and yellow nutsedge control when added to glyphosate or paraquat. In addition, trifloxysulfuron provided ex cellent pre-emergent and long term broadleaf weed control. However, trifloxysulfuron negatively im pacted cabbage vigor, and yield.

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21 CHAPTER 1 LITERATURE REVIEW Introduction Fallowing and Fallow Weed Control Fallow Land is defined as:Cropl and that is not seeded for a season; it m ay or may not be plowed. The land may be cultivated or chemically treated for control of weeds and other pests or may be left unaltered. Allowing land to lie fallow serves to accumulate moisture in dry regions or to check weeds and plant diseases. As a method of restoring productivit y, rotation of crops is now preferred to fallowing, which is considered wa steful of humus and nitrogen (The Columbia Encyclopedia). Reasons for Fallowing There are several reason s why fallow weed control is important in Florida vegetable crops including; 1) the loss of methyl bromide, and 2) the lack of weed c ontrol options during the cropping season Methyl-bromide is a soil fumigant used in many vegetable crops that provides total weed control; however it has been banned under the Montreal Protocol a nd is being phased out (VanSickle et al., 2000, Schneider et al., 2003, Deepak et al., 1996). Registered pre-plant herbicides labeled for weed control in Florida vegetable crops are selective and do not provide ade quate control of many common w eeds (Stall and Gilreath, 2005). Johnson and Mullinix (1998) reported that acceptable weed management in cucumbers is difficult because registered herbicides are genera lly not effective in controlling large-seeded dicot weeds or perennial sedges. Fewer herbicides are register ed for vegetable crops due to lower acreage and fewer herbicide sales. In a ddition, liability for herbicide manufactures is higher due to higher crop value per unit area in vegetable crops.

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22 Post-applied herbicides in vegetables often l ack selectivity and gene rally can only be used to control weeds in row middles during the cropping season. There are few labeled post emergent herbicides that can be applied over the top of the crop without either injuring the crop or provide adequate control of multiple weed species. All these r easons support fallow weed control,where there are fewer drawbacks associat ed with weed control than during the cropping season. Tillage, broad spectrum herbicides, includi ng those that translocat e within the plant and posssesing residual control may be implemented dur ing the fallow season. Weeds present during planting and early crop development have the mo st negative impact on crop yields (Knezevic et al., 1997). According to Stall (199 9), fallow weed control can also be used to reduce the seed rain of sexually propagated weeds. In a ddition, fallow treatments can be used to reduce asexually propagated weeds. Lastl y, weed control during the fallow period can play an important role in reducing diseases and in sects that are harbored between crops in susceptible alternate weed host species. Weeds: Explanations and Problems A sim ple definition of a weed is any plan t growing where it is not wanted (Anderson, 1996; Radosovich et al., 1997). We eds negatively impact crops by increasing the time and costs of production. They also interfere with mechanical and hand harvesti ng, and reduce crop yields and produce quality. Even voluntee r crop plants from a previous season can act as a weed during the following crop. In cropping systems weeds are the first plant species to colonize disturbed areas. Therefore, weeds are those plants which ar e best able to adapt to the constant changes involved in crop production such as land preparation, tillage, cu ltivation, and herbicide use (Anderson, 1996).

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23 Sexual and Asexual Reproduction Weeds that reproduce by seeds are sexually propagated. In asexual propagation the vegetative parts such as bulblets, bulbs, corms, roots, rhizomes, stolons and tubers are the reproductive organs. Many plants can propagate by both sexual a nd asexual means (Booth et al., 2003). Annual weeds are spread near and far by their seeds. Locally perennial plants are distributed by both sexual and asexual reproducti on. Perennial plants are spread far by the dissemination of their seeds. Weed propagul es are naturally disse minated by wind, flowing water, and animals. The distribution of seeds and vegetative propagules may be aided by farm and transportation equipment. Seeds are spread easily by harvesting equipment that travels from one field to another. Seeds can also be spread in contamin ated crop seeds. Weeds that reproduce asexually are spread by tillage which cuts and distributes the vegetative parts throughout the field and into other fields that the machinery is us ed in. Both sexual and asexual reproductive organs can be transported long di stances on transportation equipment such as trucks, trains, boats, and airplanes (Anderson 1996). Characteristics of Weeds There are co mmon characteristics that weeds te nd to posses, therefore plants that do not posses these characteristics are unl ikely to be classified as wee dy. These characteristics have allowed weeds to become tolerant to abiotic e nvironmental variations within the species. The ideal weed characteristics include plants tha t: 1) have seeds that can germinate in many environmental conditions, 2) have seeds that posses discontinuous germina tion and longevity, 3) grow rapidly through the vege tative phase to flowering, 4) produce seeds continuously throughout the growing season, 5) are self comp atible by not necessarily autogamous or apomictic, 6) dont require specia lized pollinators or can pollinate by wind, 7) produce prolific amounts of seeds in favorable growing conditions 8) are able to produce seeds under a wide

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24 range of conditions (tolerant and plastic, 9) are adapted for shor t and long distance dispersal 10) have vigorous vegetative reproduct ion or can grow from plant fragments for perennials, 11) are brittle and cannot be pulled from the ground t ype perennials, 12) are able to compete interspecifically by special modes such as ro settes, choking growth and allelopathy (Baker, 1974). Basically, weeds have different strategies for survival to stressful conditions and poses competitive advantages compared to other plan ts. As discussed earlier many annual weeds produce a large number of seeds to ensure futu re generations. For example, crabgrass can produce between 909 and 3,160 seeds/plant de pending on density (Aguyoh and Masiunas 2003a). Stevens (1932) investigated th e number of seeds produced by certain weeds. He found that the plant families which produced the most abundant amount of seeds averaged across species are Poaceae (annuals17,891 seeds/plant pe rennials11,640 seeds/plant), Polygonaceae (annuals-17,945 seeds/plant, perennials21,883 seeds/plant), Chenopodiaceae (annuals27,000 seeds/plant), Brassicaceae (annuals15,717 s eeds/plant), and Asteraceae (annuals3,816 seeds/plant, perennials10,833 seeds/plant). Co incidently many plants in these families are weeds precisely because they produce prolific numbers of offspring. In addition, individual weed species that produce many seeds are: Cyperus esculentus L. ( 2,420 seeds/plant), Digitaria sanguinalis (27,100 seeds/plant), Amaranthus retroflexus L (117,400 seeds/plant), Portulaca oleracea L. (52,300 seeds/plant) and Rudbeckia hirta L. (1,615 seeds/plant). In regards to seed longevity, dormancy and germination, Masin et al. (2006) found that crabgrass seed viability was re duced 5-10% during the first 3 m onths. In addition, crabgrass seed viability declined to 50% after 448-492 days. Crabgrass s eed viability was less than <1%

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25 after 1200 days. However, goosegrass seed viabi lity remained high after 3 years and values decreased to less than 80% after 1158 days. They found that crabgrass germination was higher in late spring and early summer and lower in la te autumn and winter. However, goosegrass seed did not exhibit dormancy. Germination was near ly 100% in the spring and autumn and about 85% in summer and winter for goosegrass. Crop-Weed Competition Com petition between two plants occurs when th e supply of light, water, nutrients, physical space, temperature and other factors essential to growth or development are not provided optimally for the demands of both plants (Anderson, 1996). Therefore, competition is detrimental to the growth and development of one or all of the plants competing for resources. Competition between plants can be enhanced by allelopathy, which is when the growth of one plant is biochemically inhibited by the production of phytotoxic compounds of another plant. Interference refers to all the dire ct and indirect effects one plant has on another. Characteristics of weeds that successfully compete with crops are; plants that have an aggressive growth habit, more efficiently utilize resource that are n eeded by the crop and/or produce allelopathic substances. Crop-weed competition for resources can drastically reduce crop yields and possibly crop quality. The amount of reduction in crop yields by weed competition depends on the weed species, the timing of crop-weed emergence, du ration of competition, density of weeds, crop spacing, proximity of weeds to crop, crop plantin g date (season), climatic and environmental conditions. Generally, br oadleaves are more competitiv e than grasses. However, competitiveness among grass and broadleaf species var y. Intuitively, as w eed densities increase crop yields decrease regardless of the competitive ability of a single plant.

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26 Critical Weed-Free Period The critical weed free period is the tim e during crop production that the presence of weeds has the greatest impact on reducing crop growth and yields. During this critical time period weed-control must be implemented to prevent un wanted crop yield losses. The crop should be kept weed free during this critic al period of development. Howe ver, once the crop is established and able to gain a size adva ntage during this critical period of time it can successfully outcompete later emerging weeds, mainly by shadi ng. In general, annual crop yields are most adversely affected by weed competition duri ng the first 4-6 weeks after crop planting. Therefore, weed emergence rela tive to crop emergence is important in crop-weed competition. In general, weeds that emerge before or with the crop plant compete with the crop and reduce by growth and yields. For example, early emerging crabgrass decreased yield in snap beans more than late emerging crabgrass. Densities as low as 1 crabgrass plant/m row can reduce snap bean yields when they emerge early in the s eason (Aguyoh and Masiunas 2003a). The duration of crop-weed competition is very important as well. Sometimes the growth of the plant is not hindered by a certain period of co mpetition but later yields are compromised by extended periods of competition. Weed competition can cause delayed ripening and harvests, even if total yields are not compromised. Harvesting de lays can be detrimental to farmers that are competing with each other for early season market opport unities when crop prices are highest. Monks and Schultheis (1998) conducted a critical weed-free pe riod study for large crabgrass ( Digitaria sanguinalis ) in transplanted watermelon ( Citrullus lanatus ). Their results indicated that triploid watermelon marketable weight and fruit number per hectare declined linearly the longer crabgrass compe tition occurred. In addition, hi gh densities of large crabgrass (250 to 300 plants/m2) caused a marketable yi eld decrease of roughly 5,582 kg and a loss of approximately 911 fruit for every week of compe tition. Marketable fruit yield and fruit number

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27 increased in a quadratic fashion in response to delaying the emergence of crabgrass for up to 6 weeks. Yield was increased by 880 kg and 151 fr uit per hectare for every week crabgrass emergence was delayed. Large crabgrass emer ging after 6 weeks did not affect watermelon yield. Therefore, the critical weed-free period for large crabgrass in transplanted triploid watermelon is between 0 and 6 weeks. Host plants for pests Weeds m ay act as an alternate host for insect s and diseases to overwinter and re-infest crops (Anderson, 1996). Many insects and diseases us e weed species related to the crop as an alternate host, this is true for tomatoes and solanaceous weed s. Mossler et. al, (2006) described nightshade and dodder as common weed s in pepper that facilitate diseases American black nightshade ( Solanum americanum ) is a broadleaf weed that serv es as an alternative host for nematodes, diseases, and virus-vect oring insects. Another weed that is problematic in peppers is dodder. Dodder is a parasitic plant that infect s crops or weeds. If dodder is growing on an infected pepper plant, it is capable of bridging the disease to another he althy pepper plant within the row (Mossler et al., 2006). Weed species in the solanum family incl ude nightshade species, buffalo bur, and horsenettle. These plants are suitable hosts for pests that attack sola naceous crops such as tomato, pepper, and potato. Pests of solanaceous crops include whiteflies, various viruses, Colorado potato beetle, and cabbage looper. Mo rningglories can serve as a host to pests that attack sweet potatoes such as th e sweet potato weevil. Beet we stern yellows virus can be found in pigweeds. Purple nutsedge and goosegrass can become infected by barley yellow dwarf virus. In addition, many weeds can serve as host plant for insects that are widespread and not host specific.

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28 Common and Troublesome Weeds in Vegetable Crops The Southern W eed Science Society Proceed ings (1999) indicate that the ten most common weeds in Florida vegetable crops are pigweed spp., yellow nutsedge, common lambsquarter, goosegrass, panicum, nightshade, common ragweed, common purslane, crabgrass, and Florida pusley. The ten most troublesome weeds in Florida vegetable crops are yellow nutsedge, purple nutsedge, parthenium, nightshade, morningglory, eclipta, common ragweed, common bermudagrass, Brazilian pusley, and sicklepod. Webster and MacDonald (2001) performed a farm er survey in Georgia of different crops and compiled a list of the most troublesome weeds. In Georgia vegetable crops nutsedge species (purple and yellow) were listed as the most troublesome weeds, followed by pigweed species, sicklepod, swinecress, cutleaf eveningprimrose, w ild radish, bristly starbur, Texas panicum, Florida beggarweed, and tropic croton. Holm et al. (1977) wrote a book on the world s worst weeds. Many of the problematic weeds throughout the world are f ound in Florida vegetable crops. Some of these weeds include: Cyperus rotundus L., Eleusine indica (L.) Gaertn., Portulaca oleracea L., Digitaria sanquinalis (L.) Scop., Amaranthus hybridus, and Cyperus esculentus L. Listed below are descriptions of these weeds. Cyperus rotundus L. Cyperus rotundus L. is a m ember of the Cyperac eae (sedge family) and is commonly known as nutgrass, nutsedge or purple nutsedge. Purple nutsedge is the worlds worst weed. (Holm et al., 1977). This sedge is native to India. The leaves ar e very dark green, the stem is three-sided, the plant grows up to 100 cm tall on moist fertile soils a nd it has an intricate underground system of rhizomes and tubers. In fact, the rhizomes are known to penetrate and gouge through root crops. Purple nutsedge produces prolific subterra nean tubers that can

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29 withstand harsh weather conditions such as heat, drought and flooding through dormancy mechanisms. The inflorescence is reddish to purpl ish brown, this is the premise for its common name of purple nutsedge. Purple nutsedge is a weed that infests 52 crop s in 92 countries (Holm et al., 1977). Neeser et al (1997) conducted a study on the survival and dormancy of purple nutsedge and found that purple nu tsedge has the ability to re enter dormancy after already sprouting. Therefore nutsedge has primary and secondary dormancy. Siriwardana and Nishimoto (1987) investigated the distributi on of propagules within the soil profile. They reported that the number of purple nutsedge tubers decreased with soil depth. The vast majority of nutsedge t ubers are present in the top 15 cm to soil. Six weeks after rototilling and irrigating the so il the distribution of purple nutsedge at various depths are as follows: 45% of tubers are located in the top 4c m of the soil profile, 34 % of tubers are between 4 to 8 cm soil depth, 16% of tubers are between 8 to 12 cm soil depth, 4% of tubers are located between 12 to 16 cm soil depth and only 1 % of tubers are located betw een 16 and 30 cm of soil depth. The fresh weight, dry wei ght, and percentage of dry matte r per tuber increased with soil depth. They explained that purple nutsedge ma y store more carbohydrate re serves deeper in the soil as a survival mechanism during environmen tal stress conditions which tend to fluctuate more dramatically near the soil surface. Six we eks after field preparation and irrigation, 51% of the nutsedge tubers were from the parent popula tion (70% were connected to aerial parts and 30% did not sprout), 16 % were from new tube rs and 33% were new corms. Six weeks after tillage the relationship between the number of total tubers and the tuber number in a chain decreased exponentially. In other wo rds, most of the tubers were not attached to other tubers and the number of tubers that were contained in large chains were very small.

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30 Eleusine indica (L.) Gaertn. The common nam e for Eleusine indica is goosegrass and it belongs to the Poaceace (grass) family. It is a densely clumping annual grass and is one of the most serious weedy grasses of the world. The origin of goosegrass is disputed, howev er it is thought to ha ve come from China, India, Japan, Malaysia, and Tahiti. The distribution of this weed ranges for Natal in South Africa to Japan and the northern border of the United Stat es. It is a weed problem in 46 crops in 60 countries. Beneficial uses of goosegrass include it s use as a hay and silage in some regions of the world and that it is grown for seed s in Africa and Asia (Holm et al., 1977). Portulaca oleracea L. Portulaca oleracea is a m ember of the Portulacaceae (p urslane) family and is know as common purslane. It is an annual herb that ha s succulent, fleshy stems that can grow either upright or prostrate depending on the light conditions. It is th ought to originate from Europe, however its succulent nature suggest that it is a desert plant or a desert border plant and therefore it may be native to North Africa. It is a weed in 45 crops of 81 c ountries. Since it was one of the early vegetables it was distributed by man from pl ace to place. It has been widely used as pig food (Holm et al., 1977). Digitaria sanguinalis (L.) Scop. Digitaria sanguinalis commonly known as large crabgrass is a member of the Poaceae (grass) family. It is an annual grass that is a problematic weed worldwide that thrives in both temperate and tropical climates. It is native to Europe and has a wide distribution extending from latitude 50 N to 40 S. Crabgrass is a weed in 56 countries and is found in 33 crops. Sometimes this grass is used for gr azing and for hay (Holm et al., 1977).

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31 Amaranthus hybridus Amaranthus hybridus commonly known as pigweed and sm ooth am aranth belongs to the Amaranthaceae (amaranth) family. The annual herb has an erect growth habit and is native to North America. It is found throughout the Amer icas and has spread to Africa and south-central Asia. It is reported to be a w eed in 27 crops in 27 countries. It is often consumed as a green vegetable in southern Africa and India (Holm et al., 1977). Cyperus esculentus L. Cyperus esculentus also known as yellow nutsedge is in the Cyperaceae (sedge) family. It is a light green perennial sedge with three-sided stems and it can grow up to 1 meter tall. Basal bulbs are formed by the swelling of the stem unde rneath the ground and rhizomes grow from this bulb to a single terminal underground tuber. Distinguishing characteristics between yellow and purple nutsedge is that yellow nutsedge has a yell ow inflorescence and produces a single tuber per rhizome, contrasted with purple nutsedge that has a purplis h inflorescence and produces rhizomes with multiple darker colored tubers in a chain. The rate of propagation is very fast for yellow nutsedge. One tuber can produce 1,900 plants almost 7,000 tubers, and cover an area of approximately 2 meters in diameter within a sing le year. The sweet, oily, fleshy tubers can be used for human consumption. The weed has been cultivated to produce tubers for pig feed. Yellow nutsedge is a weed in 21 crops in more than 30 countries around the world (Holm et al., 1977). Negative Impact of Weeds in Various Crops Weeds have different growth habits, morphol ogical structures, and survival techniques which cause them to compete differently with between crops. Season long competition of 8 crabgrass/m row reduced snap bean yields from 46 to 50% (Aguyoh and Masiunas 2003a). Aguyoh and Masiunas (2003b) also found that 8 re droot pigweed plants/m row reduced snap

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32 bean yield 39 42 % for early emerging weeds (weeds seeded with the crop). Late emerging redroot pigweed (seeded at the first trifoliate le af stage) reduced snap bean yields between 48 58 % at the same density. Santos et al. ( 1997) found that season long interference of smooth pigweed and common purslane cau sed a reduction of field grown lettuce yields of 24 and 48% respectively. These yield reductions occurred when pigweed density was between 8 and 16 plants per 6 m of row and purslan e density was 16 plants per 6 m of row. Santos et al (2004) described the mechanisms of smooth pigweed and common purslane interf erence with lettuce as influenced by phosphorous. They concluded that smooth pigweed interfered with le ttuce primarily due to light interception from its taller canopy. Luxur y P absorption by pigweed was a secondary interference mechanism with lettu ce. In contrast, common pursla ne primarily competed for P, and due to the increased canopy height, light interception became a secondary interference factor. Thus banding P instead of broadcasting may reduce the lettuce yield losses from competition by smooth pigweed, and common purslane. Kadir et al (1999) concluded that 7.4 purple nutsedge/ft2 reduced tomato yields 14% when competing for the entire growing season. Mora les-Payan et al. (1997a) found that 18.6 purple nutsedge/ft2 reduced bell pepper yields by 32% wh en allowed to compete season long. Johnson and Mullinix (1999) found that 1.4 yellow nutsedge/ft2 allowed to compete all growing season decreased cucumber yields by 5%. William and Warren (1975) found that season long competition of purple nutsedge at high densities reduced yields of garlic by 89%, okra by 62%, green bean by 41%, cucumber by 43% and cabbage by 35% in experiments conducted in Brazil. In 1997, Morales-Payan and Stall demonstrated that full season competition with purple nutsedge decreased eggplant yields by

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33 22%. Morales-Payan et al. (1997b) found that purple nutsedge caused up to 40% yield loss in tomato in experiments conducted in the Dominican Republic. Buker et al. showed that full season ye llow nutsedge competition reduced watermelon yield by 98%. According to Dusky et al. (1997) rice yields were reduced by 23% due to season long competition with yellow nutsedge. Keeley and Thullen (1975) reported that yellow nutsedge allowed to compete for the entire grow ing season reduced the yield of cotton by 34%. Morales-Payan et al. (2003) conducted a st udy to determine the above and below ground interference of purple an d yellow nutsedge with tomato. Th ey found that dry tomato shoot weights decreased with full (both above and below ground competition), aboveground, and belowground interference with purple nutsedge. Full competition decreased tomato shoot dry weight by 28 % compared to tomato plants grown without purple nutsedge competition. Below ground competition with purple nu tsedge decreased tomato dry shoot weights by 15%. Morales-Payan et al. (2003) tomato plants in full or above ground competition with yellow nutsedge were 20% taller than tomatoes grown without yellow nutsedge competition and tomatoes competing underground with yellow nutse dge. This effect was at tributed to tomato elongation to outcompete yellow nutsedge for su nlight. Full yellow nutsedge interference decreased tomato shoot dry weight by 34%. Above or belowground competition with yellow nutsedge decreased tomato dry shoot weights by 19% compared to the weed free tomato check. The authors concluded that purple nutsedge primarily competed with tomato by underground interference. However, in yellow nutsedge both above ground and belowground interference with tomato were important. Methyl Bromide Alternatives Methyl brom ide is a broad spect rum fumigant that has been id entified as essential for the production and marketing of many fru it and vegetable crops, it is used for the control of a variety

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34 of soil-borne pests and pathogens (VanSickle, 2000, Deepak et al., 1996). This chemical is used as a pre-plant material and is us ually combined with chloropicrin to manage several soil-borne pests and pathogens that include nematodes, fungus, insects, weed seeds, and weed vegetative propagules (specifically nutsedge) in high value fruits, nuts, vegetables, nursery and ornamental crops (Deepak et al., 1996; Schneid er et al., 2003). In addition it is used for the post-harvest control of pests and pathogens on fresh produ ce and durable commodities (Schneider et al., 2003). It can also be used to control termite s, cock roaches, and rodents in buildings. Methyl bromide is injected into the soil duri ng soil preparation. It is then covered by polyethylene film that prevents the escape of this volatile gas. The polyethylene mulch will then serve as a barrier to prevent weed growth and moisture loss from the soil. In this plasticulture system, the fumigated area is left for two weeks (10-14 days), before holes are punched into the mulch and transplants are planted. A second crop may be planted into the same plastic mulch depending on the condition of the mulch and the market conditions (Deepak et al., 1996). The reason the use of methyl bromide was so prevalen t is because of its effectiveness and economic feasibility to contro l many pests with only one applic ation prior to planting the crop. Unfortunately, methyl bromide ha s been designated as a Class I ozone depleter (Deepak et al., 1996; VanSickle, 2000, Deepak et al., 1996). Therefore, methyl bromide has been banned under the Montreal Protocol (an in ternational treaty) and the US Cl ean Air Act, and is gradually being phased out. Originally the U.S. Clean Air Act of 1992 required that Class I ozone depleting chemicals be banned within seven years of their classification, thus U.S. regulators issued a complete ban on methyl bromide by January 1, 2001. Since January 2001, methyl bromide use was restricted to 50% of the amount used in 1991. In 2003, the available amount of methyl bromide was restricted to 30% of the 1991 levels and a complete ban was imposed in

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35 2005, excluding quarantine uses. (Schneider et al., 2003; VanSickle, 2000; Deepak et al., 1996). This leaves Florida vegetable gr owers in a serious dilemma, since pre-plant soil fumigation is a standard procedure in high value vegetable cr ops such as strawberries, tomatoes, peppers, eggplant, cucumbers, squash, and watermelons. These include crops that are used in a double cropping system in Florida, meaning a primary crop (tomatoes, peppers, eggplant) is produced and the inputs from the primary crop are utili zed to produce a second crop of shorter maturity (cucumbers, squash, watermelon) on the same area of land. Naturally a ban on methyl bromide may affect the production of these crops (VanSick le et al., 2000, Deepak et al., 1996). A methyl bromide ban will be even more detrimental to Florida production for winter crops, since Florida is the state that supplies the majority of vegeta bles to the U.S. market during November through May. Critical use exceptions have been issued for certain crops However, the critical use exemptions have to be reinstated and will eventu ally expire and alternatives to methyl bromide need to be developed. Unless there is a silver bullet broad spectrum cure all that can replace the role methyl bromide has served in the past, it seems a silver buck shot integrated approach is needed to control specific pests. To c ontrol a specific pest, a management strategy must 1) effectively control the pest, 2) prove effective under local so il conditions, 3) be economically feasible and 4) be environmentally friendly. Possible solutions that meet this criteria to control specific pests include plant growth promoting rhizobacteria, su ppressive soils, soil amendments, mulches, crop rotation, host resistance, new chemicals, and new application techniques for chemical alternatives, biological control, and fallow (Schneider et al 2003). Scientists at USDA sponsored meetings identified methyl bromide a lternatives that growers will most likely adopt and the expected impacts these alternatives will have on costs and yields of several crops. In

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36 general, Florida growers were predicted to switch to a fumigant and herbicide combination (1,3dichloropropene/chloropicrin/herbicide) as a re placement to methyl bromide (VanSickle et al., 2000). This speculation is confirmed by Deepak (1996), who suggests that a fumigant such as Telone or Vapam would be used to control nematodes and diseases and a herbicide would be used for weed control. He found that the pr e harvest production costs per acre differ slightly between methyl bromide and no methyl bromide systems. However, the main impact of the methyl bromide loss would be on the reduction of yields per acre. Telone or Vapam coupled with a he rbicide will provide an inferior control of weeds compared to methyl bromide, especially nutsedge. The loss of methyl bromide would also make vegetables more susceptible to soil -borne pests. In double cropping systems the first crop yield reductions range from 15-40% and th e second crop yield losses would be higher ranging from a 20 to 50% reduction. The larger yield losses are attributed to the projected degradation of the plastic mulch in the second crop due to reduced weed control. In Palm Beach and Dade counties the projecte d yield losses from a methyl bromide ban are greater because of less land available for produc tion. Areas in southwest and west central Florida would be able to move production and escape the old land disease (Deepak et al., 1996). Production would cease in Palm Beach county for tomatoes, peppers, eggplants, and cucumbers. In addition, the production areas in th e southwest and west ce ntral areas of Florida would be adversely affected, howev er west central Florida would remains substantial producer of tomatoes and peppers. Much of the production lo ss in Florida would be gained by the Mexican fresh vegetable industry. Florida is expected to retain a majority of the green pepper market in April and May. Both Texas and Mexico are expect ed to gain market share, since neither region is affected by the ban on methyl bromide. Fl orida FOB (Freight On Board) revenues from the

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37 six major crops (tomato, pepper, eggplant, cucu mber, squash, watermelon) are projected to decrease by 53% and Mexican FOB revenues for th ese crops are projected to increase by 65%. FOB revenue from bell pepper will more than doubl e in Texas. On average the whole sale price of peppers is expected to increase by 4 % acros s the U.S. due to a ban on methyl bromide. The southeast and northeast markets are expected to s ee the greatest price increase due to the methyl bromide ban and the decreased Florida production of fresh winter vegetabl e crops (Deepak et al., 1996). As a logistical problem, it should be not ed that Telone requires additional personal protective equipment by applic ators and field workers. Pepper growers in Florida are assumed to switc h to a Telone C17/Devrinol combination. Predicted pre harvest cost s of this alternative range from a decline of $41 per acre in West Central Florida to an increase of $397 per acre in Palm Beach County. Furthermore, pepper yields are expected to decline 25% in Dade Count y, because of the restrictions on Telone use in that area, but the yield is predicted to decline 15 % in all other areas of Florida. Due to the ban on methyl bromide the acreage of bell peppers in Florida is expected to experience a 65% decline. This will lead to increased pepper production in Texas and Mexico, since neither of these areas use methyl bromide as a predominan t production practice. Ev en with the increased acreage in Mexico and Texas, total pepper pr oduction is expected to decline by 12.3% and wholesale bell pepper prices are predicted to incr ease by 4.5%. Lastly, a decrease of $37.8 million is expected for the loss of total shipping point revenues for peppers, with Florida suffering a $134.8 million loss in shipping point revenues. Florida shippers may lose $218.4 million in shipping point revenues across all crops, if better alternatives to methyl bromide are not found. Due to the decline in produce quantity and an increas e in the price paid for those products, the consumer surplus is expected to decline by $111.7 million dollars due to the ban of

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38 methyl bromide (VanSickle et al., 2000). Deepak et al. (1996) also suggest that a ban on methyl bromide would not only hurt producer s but consumers as well. In addition, he suggests that Mexico will provide the bulk of the U.S. winter vegetable mark et in the void that a ban on methyl bromide would create. Since the resulting economic impact from the loss of methyl bromide will be severe, we need to explore new alternatives to maintain our vegetable production in Florida. In summar y, the availability of methyl br omide has drastically decreased, its cost has dramatically increased, and it will be gone someday. In order to control the pests and diseases that methyl bromide successfully hindered, an integrated approach has to be taken. Individual methods may have to be implemented to control each individual pest separately. One feasible option to lower the weed pressure prior to planting (and thus increase crop yields) is to implement fallow weed control methods that utili ze herbicides and/or tilla ge. Fallowing can also be used to decrease disease pr essures in cropping systems. Tillage Soil disturbance is the simplest and oldest m e thod of weed control. Many countries today still rely largely on mechanical tillage, hand hoeing, and pulling weeds as the primary method of controlling weeds. Tillage disturbs the roots and hinders the plants of the ability to uptake water and nutrients necessary for growth. However, tillage can cause a shift in the weed spectrum to favor rudimentary species that are adapted to constant disturbances. Tillage can be used successfully alone to control cer tain weeds, but other weeds ca n thrive under these conditions when competition is removed. Seeds within the soil can be either buried by tillage or can be brought to the surface. Buried seeds will remain dormant, not germinate, and eventually die. Seeds that are brought to the surf ace will have the opportunity to germinate and this is the reason tillage causes a flush of weeds when implemented. Creating a situation where a flush of weeds is induced is a helpful management tool to kill emerging weeds all at once.

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39 However, tillage can have negative impacts on weed control efforts. Cultivation can propagate vegetative materials by cutting them into pieces and depositing them into the soil. Mechanical tillage is easily implemented on fallo w land. However, in a crop, tillage can only be performed in row middles and will not remove weeds within the row. Supplemental hand weeding, hand hoeing, or selective herbicides are n eeded to control weeds near the crop plants. In summary, tillage is a good t ool to control certain weeds under certain situations but additional tools are need to effectively manage w eed pressure in vegetable crops. Seed Bank (Survival and Dormancy) The soil seed bank represents the seeds that are in the soil profile. Understanding and m anaging the soil seed bank is a necessity to weed control. Some seeds have mechanisms which allow them to remain viable in the soil for a long period of time, whereas some seeds are short lived in the soil. Dormancy mechanisms allow seeds to remain in the soil without emerging until environmental conditions are favorable. Seeds a nd vegetative reproductive parts have different survival and dormancy mechanisms. In general, seeds can survive longer than vegetative structures. In order to effectively manage th e seed bank, seed rain, seed dormancy, and seed survival must be taken into account for each spec ies. If the weeds are killed before matutation and seed production then less offspring will be depos ited into the soil. Therefore it is important to control weeds before seed set and/or sp read through vegetative propagation. Understanding dormancy is critical to weed control because different environmental cues are needed to break dormancy. If these cues are not provided than th e seed will remain dormant and not produce an unwanted weed to compete with the crops. In contrast, if the seed is stimulated to emerge and then the plant is killed then the soil seed bank will be depleted. Lastly, only viable seeds can produce viable offspring, therefore if the seeds or vegetative propagules are killed by predation, chemicals, diseases, or stressful environmental conditions than they will not reproduce. Seed

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40 survival varies between species and environmen tal conditions. Some species can survive for many years in the soil, while others cannot. Understanding the seed bank and dormancy will allow the implementation of differe nt weed control strategies. Fallowing is an excellent way to hinder weed seed production and to deplete the soil seed bank. Webster et al. (2003) conclude d that the predominant grass species present in their study were related to either soil seedbank or a combination of soil seedbank and seed rain. They provide multiple regression equations models, which show the seedling recruitment of large crabgrass is related to the soil seedbank (r2 = 0.44 to 0.5), seed rain (r2= 0.36 to 0.41), and combination of both factors (r2 = 0.43 to 0.69). Pearsons correlation coefficients show that seed rain and soil seedbank are related (r2 = 0.41 and 0.68). Seedling recruitmen t for large crabgrass was between 6% to 41% of the soil seedbank depending on year. Stale Seed Bed A m ethod similar to fallowing used to control the soil seed bank is the stale seed bed. A stale seed bed is when weeds ar e allowed to emerge and then killed prior to planting a crop. Johnson and Mullinix (1998) defined stale seedbed as a seedbed prepared days, weeks, or months prior to seeding or tran splanting a crop. They also found that shallow tillage of stale seedbeds prior to planting improved weed cont rol in cucumber. Florida pusley and yellow nutsedge densities were lowered in plots that were tilled twice duri ng the stale seedbed. Furthermore, shallow stale seedbed tillage c oupled with a basic weed management program eliminated the need for additional herbicides for cumber production. However, Florida pusley was not effectively controlled by a stale seedbe d glyphosate application made directly after cucumber seeding. The authors stated that once refined, stale seedbed offers the possibility of improving overall weed management because it do es not depend on new herbicide registrations and uses commonly available equipment.

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41 A study using stale seed bed techniques using glyphosate significantly reduced density and biomass of the principle broadleaf species (common purslane) (Caldw ell and Mohler, 2001). The authors also found that a singl e application was just as eff ective as two applications of glyphosate. In essence, fallow weed control is similar to a stale seed bed because it kills emerged weeds and depletes the amount of viable seeds in the soil profile. Stale seed beds and fallowing are an important integrat ed weed management approach. Lonsbary et al. (2003) found that seed bed pr eparation between 10-30 days before planting which was sprayed with glyphosate plus glufos inate ammonium after seeding and before cucumber emergence had higher yields than the c ontrol (0 days before planting) seedbed In addition, they found that seedbed preparation can be extended to 40 days before planting, however an application of glyphosate was needed at 20 days before planting to provide optimal cumber yields. Herbicides Labeled for Fallowing -Post Emergence Applications Halosulfuron-methyl Halosulfuron-m ethyl (methyl 3-chloro-5-[[[[(4, 6-dimethoxy-2pyrimidinyl)amino]carbonyl]amino]s ulfonyl]-1-methyl-1H-pyrazole-4 -carboxylate is a selective herbicide used to control various broadleaves and nutsedges. This herbicid e is a member of the sulfonylurea family. The mode of action is inhi biting the ALS (acetolactate synthase) enzyme in plants (Senseman 2007). According to the label (Gowan Company) it is recommended to use a variety of cultural, mechanical, and chemical weed control techni ques to avoid development of ALS herbicide resistant weeds. Cultivation should be delayed for at least 7-10 days follow ing an application of halosulfuron. A non-ionic surf actant is recommended as an adjuvant for post emergent applications. Tank mixtures are allowed, but ma ny have not been evaluated. Tank mixtures of

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42 halosulfuron and glyphosate plus a non-ionic surfactant are reco mmended to be used as a preplant burn down material for emerged annual grasses, broadleaf w eeds, and nutsedge in sugarcane and Pioneer IR corn hybrids. A suppl emental label for tank mixing halosulfuron with EPTC has been approved for use on snap beans to allow a greater spectrum of weed control. This herbicide should not be applied to st ressed plants caused by drought, flooding, nutrient deficiency, disease, insect da mage or other inferior grow ing conditions. Two sequential applications may be made per season. It is important not to exceed 0.125 pounds active ingredient of halosulfuron per acre in a singl e season in a fallow ground scenario. Avoiding rainfall or irrigation for at le ast 4 hours following a foliar application will improve efficacy. Crop maturity can be delayed due to halosulfur on applications. Halosulfuron can cause temporary yellowing and stunting of the crop as well. In the weed symptoms can be seen shortly after application. First susceptible weeds experi ence growth inhibition. Then the leaves and growing points become discolored. Weed death can be expected within 7 to 14 days depending on the species, size, and growing conditions of the plant. Actively growing broadleaf weeds should be should be treated at a height of 1-3 in ches. Nutsedge should be treated at the 3 to 5 leaf stage. Multiple applicati ons are needed for annual weeds that have multiple flushes of seedlings and perennials. Since halosulfuron has resi dual activity, time intervals between last application and planting have been established for specific crops. The time interval before planting snap beans is 2 months, cabbage is 15 months, and pepper transplants is 4 months in Florida according to the label. Earl et al. (2004) found that gross carbon assimilation of yellow nutsedge decreased 30% compared to the pretreatment carbon assim ilation rate 11 days after being treated by halosulfuron. In addition, re spiration rates were significantl y different than control 11 DAT

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43 when treated with halosulfuron. Halosulfuron significantly decreased the daily whole-plant water use from 6 DAT to the end of the experi ment compared to MSMA, mesotrione, and the untreated plants. Shoot regrowth decreased by 95 to 100% after being treated by halosulfuron. Therefore, halosulfuron is effec tive at killing tubers and rhizom es of treated yellow nutsedge plants. Halosulfuron controlled yellow nutsedge in cantaloupe production 85 to 97% at 3 and 6 WAT depending on rate and number of applicatio ns (Brandenberger et al. 2005). In a study conducted by Johnson and Mullinix (2005) halosulfuron provided 88% control of yellow nutsedge which was significantly higher than the control provided by clomazone (67% control). In addition, smallflower morningglory was cont rolled 86% with halosu lfuron and 77% with clomazone, which was significantly different. Halosulfuron was the least injurious herbicide to cantaloupe in the trial (compare d to sulfentrazone and clomazone ). They also found that post transplant over the top applica tions of halosulfuron significantly injured transpla nted cantaloupe plants. However, there was no significant cantal oupe injury when halosulfuron was applied pre plant incorporated or post dir ect sprayed. There were no sign ificant differences in yields between halosulfuron, clomazone, or the untreat ed control. The authors concluded that halosulfuron adequately cont rols yellow nutsedge and many dicot weeds w ithout injuring cantaloupes, when applied pre plant incorporated or post directed. Nelson and Renner (2002) found that field applic ations of halosulfuron controlled yellow nutsedge 97%. In addition, glyphosate plus halosulfuron did not increase yellow nutsedge control and did not reduce shoot de nsity, dry weight, or height compared to halosulfuron alone. Tuber sprouting was reduced by 19% by halosulfuron comp ared to the untreated control. Halosulfuron provided more than 80% reduction of tuber densit y and fresh weight comp ared to the untreated

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44 control. The authors provided several conclusi ons from the study. They concluded that weed control ratings late during the season were a good indicator of tuber density the following spring. In addition, tuber fresh weight and tuber density were correlated, thus the tuber density can be estimated by the fresh weight. Yellow nutse dge reproductive potential could be reduced by halosulfuron after one cropping s eason and long term yellow nutsedge control may be achievable by understanding tuber behavior. Yellow nutsedg e control may be increased by using a pre emergence herbicide such as s-metolach lor plus a post emergent herbicide. Glyphosate Glyphosate (N-(phosphonom ethyl) glycine) is a foliar applied non-selective systemic herbicide used to control a broad spectrum of annual and perennial grasses, broadleaves, and sedge weeds. The mode of action for glyphosate is inactivating the EPSP (enolpyruvylshikimate-3-phosphate) synthase en zyme (Senseman 2007). The function of this enzyme is to synthesize several amino acids, which are needed to make proteins for normal plant growth and development. In summary, susceptible plants treated with glyphosate experience the inactivation of EPSP, halting the production of es sential amino acids, which ultimately results in plant death. According to the label (Syngenta Crop Protection) to achieve best results apply to annual weeds 6 inches or less in height. Perennial we ed control is generally more effective at the flowering or seed-head stage of growth. Glyphos ate is absorbed through actively growing green plant tissue. Applying glyphosate to drought-stressed weeds, weed s with little green foliage (mowed, grazed or defoliated, etc.), dusty weeds, insect or disease damaged weeds can result is sub-optimal weed control. In the case of mowed or grazed annua l weeds, allow 3-4 inches of new growth before application. In perennial weeds, allow new growth to reach the flowering or seed-head stage. The effects of glyphosate can be visibly seen in 2-4 days for annual weeds and

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45 7 days or longer in perennial w eeds. Cool or cloudy weather ma y delay activity. To increase the efficacy of glyphosate a nonionic surfact ant or approved wetting agent should be used at a rate of 0.25% v/v (1 qt./100 gals.). In addition, ammonium sulfate may increase weed control and is recommended at a rate of 1-2% by weight (8.5 17 lbs./100 ga ls. of water). Glyphosate is labeled for chemical fallow, fallow be ds, stale seedbed and post-harvest. Application of glyphosate during the fallow period prior to pl anting or emergence of any labeled crop is allowed. In addition to controlling weeds during the fallow period, glyphosate can be used to kill volunteer crop plants from the previous crop, which can serve as a host to pests and diseases. In order to cont rol problematic weeds, glyphosate can be used in conjunction with tillage in fallow systems. Tillage should be implemented no earlier than 1 day after glyphosate application and no later than 15 days after treatment. Glyphosate can be tank-mixed with oxyfluorfen herbicide for fallow use. In vegeta ble crops, glyphosate is labeled for broadcast application before planting transplants and before, during, or after pl anting but before crop emergence for direct seeded crops. Spot sprayi ng and use as a postharvest burndown material is also allowed. It is recommended to wait 3 days after application before planting peppers. Rinse residues from plastic mulch with overhead irrigation prior to punc hing holes and transplanting if glyphosate is applied to fallow beds. Toxicity ma y occur if green treated weeds are incorporated into the soil and then the crop is immediately planted. Clomazone, s-metolachlor, oxyfluorfen, and pe ndimethalin are labeled for tank mixtures with glyphosate to provide residu al pre-plant/pre-emergence weed control in vegetable crops. Glyphosate does not have any soil activity. Ther efore, weeds that emerge after application require a sequential application to control. Avoid application when heavy rainfall is likely to occur. It may be necessary to re-apply glyphosat e if irrigation or a heavy rainfall event occurs

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46 shortly after the initial ap plication. Wait at least 3 days before mowing or tilling the treated area to insure optimum weed control. Gylphosate is not volatile, therefore does not turn into vapor and drift after application. The label does not require any rotational cr op restrictions following application. Glyphosate can be absorbed by any vegetation including leaves, green stems, exposed nonwoody roots, or fruit of desirable plants. Use higher labeled rates, application volumes, and pressures when weed vegetation is dense or large. Do not exceed 4.8 qts./A of a 5 lbs/gal material in crop areas. Weeds with natural resi stance to glyphosate are present in the wild population and repeated use of the same group of herbicid es will select weeds that are re sistant to glyphosate. Certain horticultural practices can be us ed to reduce the likelihood of developing resistance and to managing resistant weeds. To avoid herbicide resistance an integrated weed management strategy that rotates gl yphosate with other types of herbicides, uses full labeled rates of glyphosate, tank mixes with other herbicides, does not allow resistant weeds to produce seeds/vegetative propagules, and monitors treated weeds for loss of efficacy should be used. Annual weeds controlled by glyphosate are, but not limited to, carpetweed, corn (not glyphosate resistant), crabgrass, crowfootgrass, cutleaf ev eningprimrose, eclipta, Florida pusley, goosegrass, groundcherry, morningglory, wild mustard, black nightshade, pigweed, common purslane, redweed, southern sandbur, sick lepod, and broadleaf signalgrass. Some perennial weeds controlled by glyphosate include: bermudagrass, purple nutsedge, yellow nutsedge, and torpedo grass. Weed control results depends on herb icide rate, stag e of growth, and number of applications.

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47 Bariuan et al. (1999) conducted work with glyphosate on purple nutsedge and found that older nutsedge plants (10 weeks old) need a higher rate of gl yphosate to provide the same level of control compared to younger plants (17 d old). To achieve similar levels of control 4.48 kg/ha was needed on older plants and 1.12 kg/ha was re quired on younger plants. A rain-free period of 72 h after glyphosate applicati on is needed to prevent a loss in glyphosate activity. Oraganosilicone surfactant added to the ta nk mix did not increase glyphosate activity. Glyphosate absorption increased from 2.8% at 1 h after application to 21.4% at 168 h after application. Translocation increased from 0.43% at 1 h following application to 5.18% at 168h following glyphosate application. Nelson et al. (2002) conducted experiments to test the effect of glyphosate on yellow nutsedge. They found that yellow nutsedge dr y weight was reduced 53% with ammonium sulfate and 34% without, this was significantly different. Yellow nutsedge dry weight was not affected by spray volume. When glyphosate was injected into yellow nutsedge, plant height was reduced by 60% and control was 88%. This sugges ts that absorption of herbicides across the thick waxy cuticle is hindered and may limit c ontrol. Yellow nutsedge was controlled 53%, tuber density was reduced by 51%, tuber fresh we ight was reduced 59% and tuber sprouting was reduced 17% by field applications of glyphosate. As mentioned, yellow nutsedge was controlled 53% 8 weeks after treatment by glyphosate and this accounted for tuber de nsity reduction of 625 tubers/m2 for every 10% increase in visible control. The additi on of non-ionic surfactant, crop oil concentrate, and methylated seed oil with ammonium sulfat e did not effect yellow nutsedge control, dry weight, tuber dens ity, or fresh weight in the fi eld. When glyphosate rates were increased yellow nutsedge dry weight decreased. A 50% growth reduction was observed with a 0.46 kg/ha application of glyphosate, which is 55% of the normal use rate for glyphosate.

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48 Chachalis et al. (2001) found that glyphosat e provided 83% control of smallflower morningglory in the 2-4 leaf stage and 63% control in the 5-8 leaf stage. Sharma and Singh (2007) reported that applications of glyphosate at rates of 1.25-2.5 kg/hg provided 64-76% control of Brazilian pusley and 100% control of hairy indigo. A tank mix of glyphosate plus carfentrazone provided 93-95% control of Brazilian pusley. Siriwardana and Nishimoto (1987) concluded th at to achieve the best control of purple nutsedge, with glyphosate, it should be applied wh en the highest number of tubers are sprouted and connected to aerial parts, because glyphosate is absorbed thr ough aerial parts. In addition, glyphosate should be applied when the greatest po rtion of propagules ar e newly formed tubers, not corms because corms are not as susceptible. Therefore, glyphosate applications should be delayed until the end of the season right before leaf senescence appears. Paraquat Paraquat dichloride (1,1-dim ethyl-4,4-bipyridinium ion) is a post emergence contact herbicide that is used for pre-plant/pre-crop emergence, chemical fallow, post emergence directed, and harvest aid desicca tion in most horticultural and agronomic crops. It is used in these various situations to suppress or cont rol grass and broadleaf weeds (Senseman 2007). According to the label (Syngenta Crop Protectio n) paraquat provides good control of most small annual weeds, however perennial weeds an d larger annuals especially grasses are only suppressed. Weed control may be compromised if w eeds are taller than 6 inches. This herbicide is readily absorbed by actively gr owing green plant tissue, it in terferes with the production of superoxides which results in rapid burndown sympto ms in treated plants. Do not apply paraquat to drought stressed plants, mature woody stems or w eeds without lots of green foliage (mowed or grazed weeds). This herbicide does not have residua l soil activity, so it will not be toxic to crop

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49 plants planted after application or control weeds that germinate after appl ication. To increase the spectrum of weed control, residual herbic ides can be tank-mixed with paraquat. Due to the rapid activity of this compound on w eeds, rainfall occurring after 15-30 minutes following application will not affect weed c ontrol. A non-ionic surfactant or a crop oil concentrate is recommended as an adjuvant with paraquat. For chemical fallowing a rate of 2.5 to 4 pts per acre and a volume of at least 10 ga ls per acre is recomm ended, higher volumes may be needed for better coverage of when weed dens ities are high. In fallow areas paraquat can be applied immediately after harv est until crop emergence the next growing season. Paraquat may be applied twice per year on fallow land. Timing of application is crucial for this product, waiting for maximum weed emergence will increase w eed control. Paraquat is effective not only at controlling weeds, but also volunteer crop plants that em erge after harvest. Trifloxysulfuron Trifloxysulf uron-sodium N-[[(4,6-dimethoxy2-pyrimidinyl) amino] carbonyl]-3-(2,2,2trifluoroethoxy)-2-pyridinesulfonamide, selectivel y controls broadleaves, grasses, and sedges. The mode of action for trifloxysulfuron is throug h the inhibition of acetolactate synthase (ALS) disrupting certain biochemical processes for es sential amino acids required for plant growth (Senseman 2007). This herbicide is labeled (Syngenta Crop Prot ection) for use in cotton, sugarcane, and transplanted tomato. The level of weed control is dependent on rate, type of weed, weed size, environmental conditions, and growing conditions. The efficacy of this compound is greatly improved if it is applied to sm all, actively growing weeds th at are under favorable growing conditions. Weed control may be compromised when the soil is dry, and if weeds are large or under stress. Inhibition of growth will occur so on after application of trifloxysulfuron in susceptible weeds. The development of sympto ms which occur can be characterized by plants

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50 that turn yellow, red, or purp le after several days, followed by necrosis and death of the meristem. Plant death can be expected with in 1-3 weeks depending on the weed species and environmental conditions. Within the natural wild populat ion certain species, biotypes, and individual weeds that are resistant to ALS-inhibiting herbicides may occu r. Using trifloxysulfuron continuously, alone, over time can select for an increased presence of ALS-resistant weeds. In order to prevent or delay the establishment of ALS-inhibiting herb icide resistance certain weed management practices should be used. Using a rotation of herbicides that have different modes of action, effectively control the targeted weed, and are used at the full labeled rate will lessen the chance of herbicide resistance development in weeds. Cultural practices such as mechanical weed control techniques and hand weeding can help re duce the development and spread of herbicide resistant weeds. In tomato the rotational crop in terval after applying trifloxysul furon, as measured in days, are 360 in bell pepper (transplanted), 210 for sw eet corn, 90 in tomato, and 540 for all other crops for which a recommendation is not provided on the label. Trifloxysulfuron is not labeled for fallow applications, however it is labeled for post-directed and row middle weed control in transplanted tomatoes. In addition, this herbic ide is registered for early pre-plan t weed control in cotton. In cotton, an early pre-plant applica tion should be made in the fall at least 90 days before planting the crop to avoid injury. Trif loxysulfuron can be tank-mixed w ith paraquat or glyphosate to increase control of certain weeds when used as an early pre-plant material in cotton. Rainfall is required to activate trifloxysulfuron for soil resi dual control. In cotton a maximum rate of 0.0188 lbs ai/A should be used and in tomato a maximum rate of 0.0141 lbs ai/A should be used.

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51 In tomato s-metolachlor may be tank-mixed w ith trifloxysulfuron for post directed sprays in transplanted tomato. Glyphosate, paraquat, and S-metolachlor can be tank-mixed with trifloxysulfuron to enhance row middle weed cont rol in tomatoes. Gene rally higher rates of trifloxysulfuron should be used for larger weed s. According to the label trifloxysulfuron provides control of the following weeds: carpet weed, volunteer corn, en tireleaf morningglory, ivyleaf morningglory, pitted morningglory, tall morningglory, yellow nutsedge, redroot pigweed, smooth pigweed, redweed, wild mustard, cu tleaf eveningprimrose and sicklepod. Trifloxysulfuron provides suppression of purple nut sedge and Palmer amaranth according to the label. Good weed coverage is imperative fo r optimum weed control, this include maintaining nozzles, screens, nozzle pressure, proper spraye r calibration, agitation, and following all other labeling recommendations. A non-i onic surfactant tank-mixed with the herbicide should be used to increase efficacy of the herbic ide. Applications should be made at a boom height of 15-18 inches above the top of the canopy (not the soil su rface) of the intended plants. After applying trifloxysulfuron a minimum of 3 hours should pass before the treated weeds are irrigated or a rainfall event occurs to ensure th at the herbicide is rain-fast. Pre-emergence Herbicides EPTC EPTC (S-ethyl dipropylthiocarbam ate) is a sele ctive pre-emergent herbicide that disrupts normal germination and seedling development, it is used in multiple crops for control of many broadleaf and grass weeds. EPTC inhibits fa tty acid and lipid biosynthesis (Senseman 2007). According to the label (Gowan Company) this herbicide is intended for pre-emergent weed control, it will not effectively control established weeds. This herbicide must be incorporated, injected subsurface, or applied in the irrigation wa ter due to its volatile nature. Incorporation of this herbicide should be done to a depth of 2 to 3 inches immedi ately after application to avoid

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52 loss of this herbicide. EPTC provides control of bermudagrass, crabgrass, goosegrass, field sandbur, signalgrass, tall morn ingglory, black nightshade, carp etweed, Florida pusley, common purslane, redroot pigweed, purple nutsedge, and yellow nutsedge according to the label. Purple and yellow nutsedge require a rate of 3 pints per acre of EPTC or higher to provide effective control. Black nightshade and redr oot pigweed need a rate of 4 pints per acre to be effectively controlled. EPTC is label for pre-plant weed co ntrol in green beans in the southeastern United States. In the state of Florida, EPTC has an emergency registration to make pre-transplant applications on formed raised beds underneath plastic. In this type of a pplication the herbicide does not need to be incorporated, because the plas tic covering acts as a barr ier to volatilization. A minimum period of 14 days after EPTC applica tion should pass before transplanting tomatoes into the treated area to avoid crop injury. In California Arizona, Oregon, and Idaho a 24 (c) registration has been issued to use EPTC to suppress purple and yellow nutsedge on fallow ground. For fallow nutsedge control the soil should be moist for 10 to 14 days prior to application to initiate tuber sprouting. After tuber sprouting the soil should be cultivated and EPTC should be applied and incorporated to a dept h of 2-3 inches. After incorporation the soil should be leveled. Irrigation should be supplied 30 days prior to planting crops following a fallow application to avoid subsequent injury. For crops that EP TC is not labeled for a minimum of 90 days should pass before planting. A study conducted in Florida found that using EPTC as a fallow herbicide gave temporary control of pur ple nutsedge; excellent control 1 month after application, but not at 1 year afte r application (Bibhas and Wilcox 1969). Hauser et al. (1966) found th at EPTC provided better yell ow nutsedge control than pebulate and vernolate. In addition the method of application affected the performance of EPTC. A subsurface soil application gave better cont rol than spraying on the soil surface or

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53 incorporating. They found that depth of appli cation affect EPTC efficacy on yellow nutsedge as well. A subsurface application at 1.5 in gave be tter control than at 5.5 in. They also evaluated application equipment and found that a power driv en rotary hoe provided better control than a disc harrow for soil incorporation of EPTC. Although, EPTC provided control of yellow nutsedge they found that vernolate controlled Florida pusley better than EPTC or pebulate. In addition, peanuts were injured most by subsurface applications of EPTC. Halosulfuron-methyl Halosulfuron is usually applied post-em e rgence but it has pre-emergence activity on broadleaf weeds and sedges. According to the la bel (Gowan Company) moist soil is needed for pre-emergent weed control activity. This allows the chemical to dissolve and become part of the soil water solution that is absorbed by sprou ting seeds or vegetative propagules and emerging seedlings. Halosulfuron can be tank-mixed with other herbicides to increase its pre-emergent activity, as well as, its effectiveness on grassy w eeds. According to the label, halosulfuron has pre-emergent control of spiny amaranth, redr oot pigweed, smooth pigw eed, eclipta, goosefoot grass, black nightshade, horsene ttle, and wild mustard. Purp le nutsedge, yellow nutsedge and purslane are suppressed by pre-emergent applicati ons of halosulfuron. Iv yleaf morningglory, tall morningglory and sandbur are not controlled by pre-emergent applications of halosulfuron. Brandenberger et al. (2005) conducted field studies using halosulfuron pre-emergent on direct seeded watermelon. They found that appl ications and combinations of halosulfuron with other herbicides controlled Palmer amaranth 91 to 100% at 2 to 4 WAT and 93% to 99% at 5 to 7 WAT. Goosegrass was controlle d 100% at 2 to 4 WAT and range d from 83 to 88% at 5 to 7 WAT with clomazone plus etha lfluralin plus halosulfuron, but the authors are unsure which chemical provided control. Carpetweed was controlled 85-100% in all halosulfuron and halosulfuron plus other herbicid e mixes. Control was at least 91% for all halosulfuron and tank

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54 mixes with halosulfuron for carpetweed 5 to 7 WA T except with halosulfur on alone at the lowest rate (.02 kg/ha), which provided only 64% cont rol. All treatments containing halosulfuron controlled cutleaf groundcherry 94 to 99%. Ha losulfuron applied pre-emergent will control broadleaf weeds and in combination with other he rbicides will increase the spectrum of control for both broadleaf and grass weeds. Pre-plant herbicides labeled for vegetable crops Im plementing fallow weed control techniques in conjunction with pre-plant herbicides will complement each other and enhance the overall level of weed control. Fallowing can be used to control weeds such as purple nutsedge that are no t controlled very well by pre-plant herbicides. However, annual weeds that were controlled during the fallowing period can germinate, emerge, and re-infest crops after field preparation and planting. Therefore, using fallowing weed control method with tradition weed control methods is recommended. S-metolachlor S-m etolachlor (2-chloro-N-(2-et hyl-6-methylphenyl)-N-[(1S)-2-methoxy-1methyethyl]acetamide) is a chloroacetanilide herb icide that inhibits the biosynthesis of several plant components including fatty ac ids, lipids, proteins, isoprenoids, flavonoids. This herbicide seems to be involved in the conjugati on of acetyl coenzyme A (Senseman 2007). According to the label (Syngenta Crop Protectio n) this herbicide can be applied pre-plant surface applied, pre-plant incorporated, or pre-em ergence for selective control of most annual grasses and certain broadleaf weeds in vari ous crops including co rn, pod crops, peppers, cabbage, and tomatoes. This herbicide should not be applied soils or surfaces that are prone to wind or water erosion to avoid offsite contamina tion. In coarse or low organic soils found in much of the state of Florida, a lower rate of th e herbicide should be used. In areas with fine textured soils or high organic matter, like the muck soils in the Everglades Agricultural Area, a

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55 higher rate of S-metolachlor is needed. So me of the problematic weeds controlled by Smetolachlor which are a nuisance to production in Florida are crabgr ass, crowfootgrass, goosegrass, signalgrass, yellow nut sedge, carpetweed, eastern black nightshade, Florida pusley, and pigweed. Weeds that are partially contro lled by this herbicide in clude common purslane, eclipta, and sandbur. In this case partial control can be defined as erratic control (good to poor) or consistent unacceptable control. Poor contro l can be the result of dry weather following the application of S-metolachlor. To improve the efficacy of S-metolachlor it is recommended to till the soil when it is moist to kill germinating s eeds and emerged weeds. S-metolachlor should be applied at planting or directly af ter planting. Sprinkler irrigation or rainfall should occur within 2 days of applying this herbicide. A water vol ume of a inch is recommended for course soils and 1 inch for fine textured soils. Weed control will be compromised if adequate soil moisture is not available after application. All labeled crops may be re-planted af ter the current growing season following an application. S-metolachlor may be surface applied as an early pre-plant material for minimum tillage or no-tillage system s. If applications are made 30-45 days before planting a split application is recommended. A pplications made less than 30 days before planting can be applied as either a split or a single application. Contact herbicides such as glyphosate and paraquat can be tank -mixed with S-metolachlor for early pre-plant usage if weeds are present at the time of applic ation. For pre-plant surface applied, pre-plant incorporated and pre-emergence applications of S-metolachlor rate of 1 + ( 0.1 % OM) pints per acre is recommended for coarse texture soils. 1.2 + (0 .1 % OM) pints per acre is recommended for early pre-plant applications of S-metolachlor on co arse textured soils. This herbicide is not intended for use on soils with grea ter than an 8% organic matter (OM). This herbicide can be applied as a spray solutions using water or liquid fertilizer as a carrier. S-metolachlor can be

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56 tank-mixed with other pre-emergent herbicides including clomazone, EPTC and pendimethalin. Post emergent herbicides such as para quat and glyphosate can be tank-mixed with Smetolachlor. In beans do not apply more than 2 pts./A per cropping year. In addition to preplant incorporation and pre-plant applications in transplanted tomatoes, S-metolachlor can be applied on the soil surface to raised pressed beds prior to laying plastic (underneath the plastic) in plasticulture production systems. In tomatoes do not make applications within 90 days of harvest. Injury can be reduced in tomatoes if the herbicide application is made 7 or more days before transplanting. McNaughton et al. (2004) conducte d research on the effect of various herbicides on snap beans in Canada. They found that s-metolachlo r applied pre emergence did not cause significant visual snap bean injury at any rate for both years of the study. In addition, plant height was not reduced by pre emergence applicat ions of s-metolachlor. Als o, snap bean yields were not reduced compared to the untreated check when s-metolachlor was applied pre emergence. Clomazone Clom azone (2-(2-Chlorophenyl)methyl-4, 4-dime thyl-3-isoxazolidinone) is an herbicide used for pre-emergent control of weeds in su cculent beans, cabbage, cucumbers, watermelon, muskmelon, succulent peas, peppers, squash, sw eet potatoes and other tuberous and corm vegetables. Evidence suggests that clomazone is metabolized its active 5-keto form. The 5-keto form inhibits DOXP (1-deoxy-D-xyulose 5-phosphate synthase), which is a crucial component to plastid isoproprenoid sy nthesis (Senseman 2007). According to the label (FMC Corporation Ag ricultural Products Group) it can be applied before seeding or transplanting and after seeding but before crop emergence. It is important to plant seeds and transplant roots below the ch emical barrier at planting. Clomazone causes bleaching symptoms and death to treated plants. Clomazone can be used 30 days before planting

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57 the crop until just prior to crop emergence. In peppers (excluding banana peppers) a rate of 0.67 to 2.67 pints per acre is recommended. A lowe r rate is recommended for coarse soils. One application may be made per season According to the label at rate of 2 pints per acre (0.75 lbs. a.i.), clomazone provides control of the following weeds; broadleaf signal gr ass, large crabgrass, goosegrass, purslane, and redweed. At a rate of 2.67 pints per acre (1 lb. a.i.), the same weeds as 2 pints are controlled plus; field sandbur and Fl orida pusley. Peppers can be planted at anytime after an application of clomazone at the same rate. At the same rate of 1 lb a.i. per acre beans, direct seeded cabbage, transpla nted cabbage, and transplanted tomatoes can be replanted 9 months after the initial application. Sweet corn and direct seeded tomato can be planted 1 year after application. All other crops can be planted 16 months after application. Johnson and Mullinix (2005) concluded that clomazone is safe to cantaloupe and controls many annual weeds, however it does not adequa tely control yellow nutsedge and smallflower morningglory. Lonsbary et al. ( 2003) reported that plots that we re treated with clomazone preemergence had higher cucumber yields than the untreated control. Pendimethalin Pendim ethalin (N-(1-ethylpropyl)-3,4-dimethyl -2,6-dinitrobenzenamine) causes mitotic disruption by inhibiting the mi crotubule protein tubulin (Senseman 2007). Pendimethalin interferes with the weeds cellular division (mitosis) in the meristematic regions. Accoding to the label (BASF Corporation Ag ricultural Products) pe ndimethalin can be used for the following vegetable cr ops: carrots, corn, edible beans, garlic lentils, peas, mint, onions, dry bulb shallots, and potatoes. This he rbicide is used to control most germinating annual grasses and certain broadleaves. Low ra tes of pendimethalin should provide control of crabgrass, crowfootgrass, field sandbur, signa lgrass, Palmer amaranth, carpetweed, pigweed species, purslane, and Florida pusley according to the label. If resistan t weeds are present or

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58 develop over time to meristematic inhibiting herbic ides than an herbicide with a different mode of action should be used in rotation. Pendimethalin is most effective when it is incorporated into the upper soil surface by rainfall, irrigation, or tillage before weed s emerge from the soil. This herbicide can be applied on the surface pre-plan t, pre-plant incorporated, surface incorporated, pre-emergence, early post-emergence, post-emergence incorporated or layby treatment. Preplant surface applicatio ns can be made up to 45 days before planting. Pre-emergence applications can be made at planting and up to 2 days after planting. Pendimethalin does not kill established weeds, so tillage before application is crucial. At a ra te less than 2 lbs ai/A all crops that are labeled can be replanted within the sa me season of application. Crops that are not labeled for use with pendimethalin cannot be planted until a year after the initial application at the same rate. In edible beans, pendimethalin ca n be used as pre-plant in corporated material for chickpeas, dry beans, lima beans, snap beans, a nd cowpeas. Pre-plant incorporation applications can be made up to 60 days before planting. Pe ndimethalin can be applied either pre-plant incorporated or pre-emergence in sweet lupines. Pre-emergence applicatio ns should be made at planting or up to 2 days after planting in a seedbed th at is free of clods. In southern states with a course texture soil a rate of 1.5 pts/A is recommended for use on edible beans. Pendimethalin has a supplemental label that allows it to be us ed as a pre-plant incorporated or a pre-plant surface material before planting tomato and pepper transplants, or as a post-directed spray to transplants or established direct seeded plants In addition, this herbicide has a supplemental label for use on strawberries, refer to the label for specific information. Oxyfluorfen Oxyfluorfen (2-chloro-1-(3-e thoxy-4-nitrophenoxy)-4-(trifluor om ethyl)benzene) provides both pre-emergence and post-emerge nce weed control. The mode of action is to inhibit the enzyme PPO or Protox (protoporphyrinogen oxidase) (Senseman 2007).

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59 According to the label (Dow AgroSciences LLC) this herbicide is registered for use on broccoli, cabbage, cauliflower, fallow bed, horsera dish, mint and onions. Oxyfluorfen provides control of spiny amaranth, car petweed, large crabgrass, cutleaf eveningprimrose, cutleaf groundcherry, annual morningglory species, wild mu stard, American black nightshade, redroot pigweed, common purslane, Florid a pusley, and sicklepod. This he rbicide is labeled for pretransplant applications in bro ccoli, cabbage, and cauliflower. Th is herbicide should be applied after field preparation but befo re transplanting. Minimizing so il disturbance when planting will result in better weed control performance. Temporary initial leaf cupping or crinkling may occur in treated transplants, but the crop will outgrow this response and develop as normally. This response will be lessened if the crop leaves are not allowed to come into contact with the soil. This response may be amplified by stressful conditions from temperature, disease, fertilizer, nematodes, insects, pesticides, or storage conditions. Extremely succu lent transplants may be more pr one to develop severe injury. Older, hardened off transplants grown in bigge r cell sizes will decrease the chances and/or degree of crop injury. The recommended rate fo r oxyfluorfen is 0.25 to 0. 5 lbs active ingredient per acre. The lower rate is recommended for cour se textured soils with lower than 1% organic matter. Severe crop injury can result from using oxyfluorfen and an acetanilide herbicide (Smetolachlor) during the same cropping season. A ccording to the label the weeds controlled in cabbage at the recommended rate are carpe tweed, redroot pigweed, common purslane, and Pennsylvania smartweed. Oxyfluorfen may provid e partial control of wi ld mustard. It is recommended to apply this herbicide with groun d spray equipment with flat fan nozzles at a pressure of 20 to 40 pounds per square inch (psi). Applying a rate of oxyfluorfen higher that 0.5 lbs active ingredient per acr e per season is prohibited.

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60 Oxyfluorfen is not approved for use on direct seeded or green house grown cole crops. In addition to being labeled for ca bbage, broccoli, and cauliflower, oxyfluorfen is labeled for use on fallow beds. In fallow beds, oxyfluorfen is used as a pre-emergent or post-emergent herbicide, it can be used alone or mixed with glyphosate to control winter annual broadleaf weeds. In direct seeded legume vegetables 60 days should pass af ter application before planting in a treated fallow bed. When oxyfluorfen is applied on a fallow bed at a rate of 0.5 lb s active ingredient per acre broccoli, cabbage, cauliflower, garlic, onion, pepper, strawberries, and tomatoes should not be planted until 30 days after treatment. Treated fa llow beds should be cultivated to a depth of at least 2.5 inches before planting. At a rate of 0.5 lbs active ingredient per acre oxyfluorfen should provide pre-emergence weed control for 8 week s to susceptible species and post emergence control of these weeds until the 6 leaf stage. Ir rigation or rainfall needs to occur within 3 to 4 weeks following application to obtain the best weed control results. As mentioned earlier, a tank mixture with glyphosate will improve the efficacy of post emergent weed control. A maximum rate of 0.5 lbs active ingredient pre acre per fall ow season is allowed. In California, oxyfluorfen is labeled for use on fallow beds before tr ansplanting strawberries and peppers using plasticulture. This herbicide should be applied to the moist soil of preformed beds prior to covering with plastic. A minimum of 30 days should pass before transplanting peppers or strawberries into the treated area. General factors effectin g herbicide efficacy Weed species, size, infestation intensity, and growth stage have a profound effect on herbicide activity. Younger plants are easier to control than older plants. Herbicides are m ore effective on smaller plants than bigger plants and it is be tter to apply herbicides to weeds in their vegetative state than in their reproductive phase. Foliar herbicides will not kill mature seeds on the plant. In addition, foliar herb icides are absorbed through green tissue, so mature plants with

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61 woody stems are more difficult to control and requir e different types of herbicides to control. Herbicide rate, surfactants, numbe r of applications, time of expos ure, and environmental factors will affect the efficacy of the herbicide. In general higher rates provide greater control up to a certain level. Older nutsedge plants (10 weeks old) need a higher rate of glyphosate to provide the same level of control compared to younger plants (17 d old). To achieve similar levels of control 4.48 kg/ha was needed on older plants and 1.12 kg/ha was required on younger plants (Bariuan et al. 1999). Surfactants can increase herbicide uptake in many weed species. Surfactants potentially increase herbicide activity by maximizing the su rface area of the spray droplet and degrading waxy cuticles or allowing herbic ide penetration into woody stems. Oraganosilicone surfactant tank-mixed with glyphosate did not increase acti vity on purple nutsedge (Bariuan et al. 1999). One herbicide application may provide ade quate weed control and sometimes multiple applications are needed. This varies depending on the herbicid e and the weed species. Longer exposure times will facilitate he rbicide absorption to a certain extent. Achieving a threshold concentration of herbicide within the plant will provide the desire d weed control. Optimizing the time of herbicide exposure to th e plant will increase herbicide activity. This can be done by applying herbicides on a sunny, rain-free day. A rain-free period of 72 h after glyphosate application is needed to prevent a loss in gl yphosate activity on pur ple nutsedge (Bariuan et al. 1999). Environmental factors such as light, soil moisture and temperature will affect herbicide activity. Since herbicides are absorbed by activ ely growing plants, envi ronmental stresses that negatively impact the growth of the plant wi ll hinder herbicide uptake and performance. Herbicide absorption and translocation can conti nue to occur even a week after application. Glyphosate absorption in purple nutsedge increase d from 2.8% at 1 h after application to 21.4%

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62 at 168 h after application. Tran slocation increased from 0.43% at 1 h following application to 5.18% at 168 h following glyphosate application (Bariuan et al. 1999). However, if an herbicide is sufficiently taken up, translocated, and then an environmental stress such as drought occurs this can increase the herbicide activity on the plant. Basically, a healthy plant is better adapted to overcome stress than a sick plant. Herbicide activity on crops The ultim ate goal of applying an herbicide is to reduce weed competition to achieve higher crop yields and or quality. Herbic ides are not equally effective ag ainst all weeds. Selecting an herbicide should be tailored to reduce the historic and present weed populations in a given field. In addition, not all crops react positively when herbicides are applie d. Therefore, herbicides that either harm the crop or are not economically beneficial should not be us ed in a given production system. Crop toxicity to herbicides can be dependent on herbicide type, rate, method of application, tank mixtures, environmental conditions residual activity of herbicide, and duration after application before planting. Previous fallow work Cools and Locascio (1977) found that applicat ions of glyphosate provided a significantly linear decrease in purple nutsedge count density as the application rate increased. A second application of glyphosate further reduced nutsedge com p ared to a single applic ation. At a rate of 1.12 kg/ha one application decreased nutsedge 66% and two applications pr ovided 95% control. Glyphosate applied in the summer or in the fall provided good control. However, multiple applications of summer and fall or spring, summer, and fall provided excellent control. The spring treatment had the poorest control compar ed to the other treatment seasons. Spring applications had poor nutsedge cont rol due to tuber dormancy related to cooler soil temperatures.

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63 Germination of tubers do not occur at soil temperatures below 14C and germination rate increases with temperature. Even the untre ated control had a low nutsedge density. Independent of treatment season, all glyphosat e treatments provided significantly lower nutsedge populations 2 to 5 months after the final application. One application was not different than two applications made a w eek apart within a single season, ex cept for in the spring. In the spring this was attributed to f act that nutsedge had a longer time to emerge between treatments. The best control was provided by two applications made in consecutive seasons of summer and fall. Cools and Locascio (1977) indicated that further may show that the time between applications can be shortened. Edenfield (2000) found that fallow applications of glyphosate at 1.14 kg/ha provided better purple nutsedge control than the 0.57 kg/ha rate. In addition, seque ntial applications at the same rate to the same sized plants tended to provide higher purple nutsedge control than single applications. They found mixed results rega rding the efficacy of gl yphosate on purple nutsedge between small (8-15 cm) and larg e sized (20-30 cm) plants. The purple nutsedge populations in the untreated checks increased in numbers throu ghout the years of the study. These results are consistent with the findings made by Cools and Locascio (1977). Brecke, et al. (2005) conducted an experiment using various herbicides to control purple nutsedge in a bare ground field, homogeneously infested with purpl e nutsedge. They discovered that >80% control of purple nutsedge shoots was achieved by sequentia l applications of halosulfuron applied early post emergence followed by late post em ergence at a rate of 70g/ha; this was not significantly di fferent than a single earl y post emergence application. Another herbicide that was tested during that experiment was s-metolachlor. Smetolachlor applied pre emergence at a rate of 4,480 g/ha provided 75% control of purple

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64 nutsedge shoots. S-metolachlor applied pre emerge nce provided control of foliage, and reduced total density and viability of purple nutsedge. To tal tuber density was re duced by an average of 50% and tuber viability was reduced by an aver age of 59% by halosulfuron. They speculated that the control of shoot biom ass by mowing or herbicide applic ations (even if they are not translocated) may cause the depletion of to tal tuber number and viability by decreasing carbohydrate reserves. In the same trial, weekly mowing increased purple nutsedge control from 60% compared to non-mowed and 66% across all herbicides. Thus mowing increased purple nutsedge shoot control and may enhance c ontrol when used with herbicides. Smith and Mayton (1938) and Smith (1942) and found that frequent tillage applied every 3 weeks over a two year period resulted in the erad ication of purple nutsedge in fields on more than 10 types of soil. According to Webster (2003) infrequent tillage may have the opposite effect as frequent tillage on purple nutsedge popul ations. Explaining that it may be possible that infrequent tillage can serve to fragment tuber chains, release apical dominance and ultimately increase the number of purple nutsedge. Webster states that a key to managing purple nutsedge with herbicides is to apply when the ma ximum number of shoots are emerged, which is dependent on warm soil temperatures. He summar ized herbicides used to control purple and yellow nutsedge based into 3 categories: soil ac tivity only, foliar activity only, and both soil and foliar activity. The effectiveness of these herbicides were documented in the paper. Metolachlor a soil applied pre emergence herbicide provide d 55 % to 85 % control of yellow nutsedge and less than 20 % control of purple nutsedge. Glyphosate a foliar applied post emergent herbicide provided 55 % control of yellow nutsedge and 70 % control of purple nu tsedge. Halosulfuron and trifloxysulfuron provide both soil and foliar activity. Halosulfuron provided 85 to 95 % control of both yellow and purple nutsedge. Tr ifloxysulfuron provided 75 to 95 % control of

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65 yellow nutsedge. The amount of purple nutsed ge control provided by trifloxysulfuron was unknown. The effectiveness of these herbicides is dependent of weather conditions. Conditions favoring growth results in improve nutsedge control. While dry conditions often reduce nutsedge control. Lastly, he concluded that nutsedge control is a multi-season effort and that long-term control will require management strate gies that reduce or e liminate tuber production and viability.

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66 CHAPTER 2 FALLOW EXPERIMENT LIVE OAK, FL LOCATION Objective The objective of this study was to eff ectively and econom ically reduce the weed population during fallow periods before a vegetabl e crop is planted. Weeds such as nutsedge, which are hard to control once the crop is planted wa s of particular interest especially due to the phase out of methyl bromide. Materials and Methods The experim ent was conducted in Suwannee Valley Research and Education Center in Live Oak, FL to investigate several fallow treatme nts on weed control. The soil type at this location was a Blanton-Foxworth-Alpin Complex. The fallow experiment was a 2 x 3 factorial established in a randomized complete block design with 4 replicati ons. The two factors examined were; mechanical control and chemical control. The mechanical control was no till and tillage. The chemical control consisted of; no herbicides, glyphosate and glyphosate plus halosulfuron-methyl. The treatments consisted of combinations of these two factors for a total of six treatments which include no till/no herbicid e, no till/glyphosate, no till/glyphosate plus halosulfuron-methyl, tillage/no herbicide, ti llage/glyphosate, and ti llage/glyphosate plus halosulfuron-methyl. The dimension of each experimental unit or plot was 15 x 60 feet. All herbicides were applied using a CO2 pressurized backpack sprayer operating at a pressure of 30 PSI at an application rate of 30 gallons per acre During application the boom was held 18 in above the target weeds. Glyphosat e was applied at 1.25 lbs ai/A. Halosulfuronmethyl was applied at 0.05 lbs ai/A, this was tank mixed with glyphosate at the previously mentioned rate. All herbicide treatments contai ned a non-ionic surfactant (NIS) at a rate of 0.25

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67 % volume/volume. Two weeks after applying herbicides the tillage treatments were rototilled to a depth of 4 inches. Year 1 Fallow The experim ent was conducted in a field that had been out of horticultural production for some time. The entire field was tilled prior to the experiment. Emerging weeds within the area were evenly distributed throughout the field. All weed density measurements were made by randomly tossing a 0.5 m rectangle made of PVC pipe and counting the weed population within the perimeters of the rectangle. Initial weed density measurements were taken on 24 July, 2006. These weed density measurements were perfor med by making six random measurements within the experimental area. The c ounts for each individual weed speci es were then averaged across all measurements and were used as a representa tion for the weed population density for the entire field. The first chemical fallow treatments were applied on 26 July, 2006. The weed counts after all the first treatments were applied were ta ken on 21 September, 2006, except for the control plots which were assumed to contain the same w eed density as the initial weed counts. These weed counts were made by randomly measuring one representative sample per treatment. The second herbicide treatments were applied on the same day as the weed counts (21 September, 2006). Two weeks later the second tillage trea tments were applied. The treatments were visually rated after the s econd treatments were applied. Weed counts were taken on 30 March, 2007 prior to the preparing the field for the spring crop. Two measurements representative of the population were taken per plot before planting in the spring. Year 1 Crop Initial inten tions were to plant a crop in the fall; however it was too late in the season so it was decided to plant in the spring. In the spring the field was shank fumigated with C-35 Telone at a rate of 26 gal/A for nematode control on 8 February, 2007. The field was then rototilled

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68 from north to south across all treatments on 7 March, 2007. The field was rototilled north to south again and the beds were formed for the peppers on 4 April, 2007. The beds were formed across the width (15ft) of the pl ots and intercepted all treatments areas. Metolachlor was applied as a pre-plant, pre-emergent herbicide on 5 Ap ril, 2007. Two rows of black polyethylene mulch were laid across the beds following the metolach lor application on the same day. Bell pepper transplants were plante d on 11 April, 2007 and irrigated with an overhead sprinkler gun to get established. The peppers continued to receiv e overhead irrigation throughout the growing season. In addition to overhead irrigation the pe ppers also received drip irrigation/fertigation starting on 4 May, 2007. In addition to peppers, 4 double rows of snap beans were planted with a Monosem 2 row vacuum planter on 18 April, 20 07. The snap beans were watered solely with overhead irrigation during the fist year. The snap beans were side dressed with 300 lb/A of 13-413 fertilizer which provided 36 lbs of nitrogen on 25 May, 2007 and 8 June, 2007. A visual diagram of the experimental desi gn is depicted in Figure 1-1. The crops were sprayed regularly on a weekly basis starting on 20 April, 2007 and ending on 21 June, 2007. The weekly crop sprays consiste d of 1) Penncozeb (2.5 lb/A) or Manzate (2.0 lb/A), 2) Kocide 4.5 LF (2 pt/A), and 3) Spintor (6 oz/A) or E ndosulfan (1.3 qt/A) or Permethrin (8 oz/A). The crops were burned down with pa raquat (Gramoxone) at a rate of 2 pt/A on 1 July, 2007. The plastic mulch was removed and the plot was harrowed on 9 July, 2007. All in-row (within the black plastic mulch bed) weed count s were taken for the entire length of both rows within each treatment, since the plots are 15 ft wide and there are 2 rows, this results in 30 linear bed ft of black polyethylene mulch per treatment. In-row purple nutsedge counts were measured on 23 April, 200 7 and 2 May, 2007, since it was the only weed to emerge at the time. All in-row weeds were counted on 16 May, 2007; this includes purple

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69 nutsedge that penetrated through the plastic mulch and the weeds that emerged within the pepper planting holes. There was only one row middle since there were onl y two rows. The row middle weed counts were measured by taking one 0.5 m2 sample directly in the middle of the plot. Pepper row middle weed counts were taken on 22 May, 2007. The heights of six pepper plants per plot were randomly measured with a ruler in cm on 23 May, 2007, to determine if any of the herbicides stunted the crop. Per cent check ratings and weed counts were measured in the snap beans on 30 May, 2007. Deer damage was observed during the first cropping season in both the bell peppers and the green beans. Pepper harvests were taken from 5 plants in each row, making 10 harvested plants per treatment. The first pepper harvest was conducted on 13 June, 2007 and only marketable fruits were picked. The peppe rs were harvested a second time on 28 June, 2007 and all fruits were harvested regardless of size unless they we re physically damaged (blossom end rot, sun spots, eaten by insects/animals, etc.). Fruit weights (in lbs) were recorded for both pepper harvests in each treatment. Year 2 Fallow The fallow during the second year was conducte d the sam e as the first year, except the weeds were recounted in the unt reated controls every sampling date. The reason the initial untreated counts were taken repeatedly is because weeds such as nutsedge continue to propagate and multiply in number during the summer, especially when no treatments were applied. Furthermore, weed populations fluctuate up a nd down during the fallow period due to weather conditions, independently of the treatment effects. Therefore, recordi ng the untreated control counts during every sampling date provides a better contrast than when compared to using the weed population encountered at the beginning of the fallowing period as a base level. In addition, unlike year one, weed counts were made after each spray applic ation and cultivation event, instead of one measuremen t after both were implemented.

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70 During the second year the fallow treatments we re applied to the same exact areas as the previous year. The permanent metal stakes marking the boundaries of the treatment areas allowed identification of the plots even after the first years crop was tilled under. However, the fallow treatments were modified slightly th e second year, due to timing constraints. Halosulfuron was only applied with glyphosate du ring the first spray application. The second spray applications consisted sole ly of glyphosate for all herbicide plots. The reason halosulfuron was applied only once is because the minimum pr e plant interval crite ria could not be met between a late summer fallow application and a fall planting. In addition, cultivation was performed once the second year instead of twice. It would have been impossible to cultivate and wait for weed emergence before planting without planting too late during th e fall. The rationale behind having a fall crop was to contrast differences in weed spectrum, infestation severity, crop yields and responses to summer fallowing between growing seasons. Initial fallow weed counts were taken from two locations per plot on 4 August, 2007. The first herbicide treatments were applied on 13 A ugust, 2007. The effects of the herbicide were allowed to take place and weed counts were taken on 24 August, 2007. The cultivated plots were rototilled on 25 August, 2007. Following cultivation and weed emergence, weed counts were measured on 14 September, 2007. Glyphosate wa s applied to the herb icide treatment plots on 15 September, 2007. After the effects of the he rbicides were allowed to take place weed counts were recorded on 27 Septem ber, 2007. It was not possible to obtain weed counts from the untreated plots at this time due to the overwhelm ing size of the plants, therefore the counts from the previous weed count incidence was used. The entire field was then cultivated to prepare for planting.

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71 Year 2 Crop During the second cropping season bell peppers were planted on black plastic m ulch and snap beans on bare ground to replicate the previous years experiment. In addition, cabbage was planted during the second year on bare ground. Pl anting was delayed further than expected and thus cabbage was selected for its ability to survive winter frosts. These crops were chosen not only because they would contrast between weed control on plastic mulch vs. bare ground, but because these crops differ in sensitivity toward s halosulfuron carry-over. Another reason these crops were chosen was because different pre-plant/pre-emergence herbicides are labeled for these crops and we were interested in finding fa llow/pre-plant herbicide combinations that would be best for controlling specific weeds in each of these crops. In the first cropping season smetolachlor did not adequately control weed emergence in peppers and in snap beans. Therefore, in the second year in addition to s-metolachlor more pre-plant/pre-transplant/posttransplant/pre-emergence herbicides were included in the trials to all of the crops. The second year crop was a split plot design were the fallow blocks were the main plots and the different pre-plant herbicides were the subplots. Incons istencies in uniformity were observed using the single water gun to irrigate overhead because of the layout of the field (distance from the water gun), leaking near th e sprinkler head, and wind blowing water away. To solve this problem, drip irrigation was used for all the crops. In peppers, the pre-transplant tr eatments consisted of an untre ated control (no herbicide), smetolachlor (7.62 lbs a.i./gal material at a rate of 1 pt /A), cl omazone (3 lbs a.i./gal material at a rate of 2.5 pt/A), and EPTC (7 lbs a.i./ gal product at an application rate of 3 pt/A) These herbicides were all applied to the soil su rface after bed formation, immediately covered by plastic mulch, and remained undisturbed for 7 days prior to planting the pepper transplants. All chemicals are currently labeled or are being eval uated for pre-transplant underneath the plastic

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72 on bell peppers and the 7 day waiting period before planting was implemented in accordance with the EPTC restrictions to prevent phytotoxicity. The snap beans pre-emergence herbicide treatments included an untreated control, s-metol achlor (7.62 lbs ai/gal at 1 pt/A), EPTC (7 lbs a.i./gal at 4 pt/A), and pendimethalin (3.8 lbs a. i./gal at 1.5 pt/A). EPTC was applied before planting the beans and was incorporated to a depth of 2 inches using shallow tillage to prevent volatilization. The beans seeds were then planted in a single row using a mechanical planter. After planting, s-metolachlor and pendimethalin we re applied to the soil surface prior to bean emergence. In the cabbage, the pre plant herbic ide treatments were an untreated control, smetolachlor (7.62 lbs a.i./gal at 1 pt/A) and oxyfluorfen (4 lbs a.i./gal at 1pt/A). The oxyfluorfen was applied pre-transplant and the s-metolachlor was applied pos t-transplant over the top. In the peppers both purple and yellow nutsedge that penetrated the plastic or emerged through the planting hole were counted in each s ub-plot, which ran the width of the plot (15 LBF). In the cabbage and snap beans visual we ed control ratings of each weed were taken in each subplot. The only exception was purple and yellow nutsedge which were rated within the main fallow plots since the pre-treatments did not have such a profound effect as the fallow treatments. The ratings were percentage weed control, mean ing a rating of 0 correlates no control and 100 correlates total eradi cation of that particular weed. The first frost occurred before the bell peppers and the green beans were ready to harvest. The peppers were at first flower and the snap be ans had begun to flower when they were killed by the freeze. Since harvesting mature fruits we re not an option, we harvested the plants and took dry weights. On 3 December, 2007 five pepper plants and 1m row of bean plants were cut at ground level, placed in labeled paper bags, and dried in a drying room. The plant samples

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73 were weighed and recorded in grams. Th e cabbage was harvested on February 12, 2008 by hand, the number of heads per subplot and the total weight in lbs were recorded. Statistical Analysis Data was an alyzed using the PROC GLM proce dure in SAS. Significance was established based on the analysis of variance and the means were separated using least signif icant difference procedure. When analyzing the fallow weeds the initial counts were not included in the ANOVA model, since the counts were taken before the treatments were applied. Factors that had a significant effect were analyzed using LSD means separation. Furthermore, combinations of the factors were analyzed using one way ANOVA and means were separated using LSD as described by Marini (2003). This was done to co mpare the effect of fact orial combinations with the untreated check. Results and Discussion Fallow Period Purple nutsedge fallow Purple nutsedge was evenly distributed throughout the trial. A clear separation in nutsedge counts between herbicide treatm ents (0-8 nutsedge/m2), the untreated control (15-39 nutsedge/m2), and the cultivated control (24-78 nutsedge/m2) was seen after the second fallow treatment and throughout the rest of the fallow period (Figure 12). At least two consecutive herbicide treatments may be needed to e ffectively lower the nutsedge population. There were no differences in purple nutsedge counts before fallow applications were applied or following the first fallow applications The effect of herbicides on purple nutsedge counts were significant after the second fallow treatment applicatio ns were made. The effect of herbicides on purple nutsedge counts continued to be significant throughout the rest of the fallowing period. Both glyphosate and glyphosate tank mixed with halosulfuron reduced purple

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74 nutsedge numbers (0 to 5.88 nutsedge/m2) compared to the non herbicide treated plots (19.5 to 54.63 nutsedge/m2) during this period (Figure 1-3) In addition, there was an interaction in purple nutsedge counts between cultivation and he rbicide treated plots on the last sampling date of the fallow period during the second year. On th e last sampling date, the cultivated check plots contained the highest amount of purple nutsedge. The untreated check plots (28 nutsedge/m2) contained less purple nutsedge than the cultivat ed check plots (78.25 nutsedge/m2) (Figure 1-4). All the herbicide treated plots contained less purple nutsedge (0 nutsedge) than the untreated check (28 nutsedge) except for glyphosate combined with cultivation (2.25 nutsedge). The increase in purple nutsedge by cultivation can be explained by two factors. First, cultivation breaks up the intric ate system of underground tuber chains, releases the dormant tubers from apical dominance, and induces tuber sprouting. In addition, cultivation reduces most of the weeds that are propagated by seed and therefore reduces interspecific competition for weeds that are propagated vegetatively that are not controlled by tillage, such as purple nutsedge. However, these results are contrary to the re sults found by others, where cultivation controlled purple nutsedge by depleting the carbohydrate reserves within the tubers, and desiccating the tubers which caused them to die. The differenc e was that the tillage in these experiments was done repeatedly, which did not a llow purple nutsedge to reestablish, flourish, and continue to propagate. Another reason that would explain the inconsistencie s between past experiments was the fact that tillage during dry seasons caused purple nutsedge tubers to desiccate and die, however in this experiment cultivation was pe rformed during the Florida summer wet season. In essence, cultivation would be more promising to effectively control purple nutsedge when performed routinely and during the dry season. Implementation of cultiva tion to control purple

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75 nutsedge in Florida during the summer fallow pe riod, may not be economically or logistically feasible. Glyphosate and glyphosate plus halo sulfuron provided excellent purple nutsedge control. They are known to translocate throughout th e plant and destroy the underground portions of nutsedge. Since glyphosate alone provided excellent control in our experiment (better than expected) the addition of halosu lfuron may not be needed to increase purple nutsedge control. Yellow nutsedge The experim ental field was uniformly covered with a high number of yellow nutsedge at the beginning of the trial (73 yellow nutsedge/m 2) (Figure 1-5). After only one fallow treatment was applied the numbers of yellow nutsedge we re dramatically reduced compared to the untreated control. Furthermore, cultivating an d/or herbicides reduced the number of yellow nutsedge compared to the untreated contro l throughout the both fallowing seasons. Analysis of variance indicated that there wa s a significant interac tion in yellow nutsedge counts between herbicide and cultivation.. The reduction in yellow nutsedge counts was significant after the first fallow treatment was ap plied (Figure 1-6). A ll fallow weed control methods reduced yellow nutsedge (0.5 to 6.5 ye llow nutsedge/m2) compared to the untreated control (73 yellow nutsedge/m2). Compared to purple nutsedge, yellow nutsedge was relatively easy to control. Yellow nutsedge does not ha ve an extensive system of multiple underground tubers on rhizome chains, but instead only has one te rminal tuber per rhizome. This difference in morphological structure is likely the reason why yello w nutsedge is controlled by either tillage or herbicides after only one fallow treatment. Florida pusley fallow The initial counts of Florida pus ley were sim ilar for all treatm ents. After the third fallow treatment (first treatment of the second year), a pattern in Florida pusley counts starts to emerge

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76 between the untreated control, cu ltivated control, and herbicid e plots that continues for the remaining fallow period (Figure 17). The untreated plots cont ained the highest pusley counts (138 270 pusley/m2), the cultivated check ha d a moderate amount of pusley (49 164 pusley/m2) and the herbicide plots had the leas t amount of pusley (0.25 15 pusley/m2). There were significant differences in pusley counts due to fallow herbicides. After the second fallow treatment and through out the rest of the fallow peri od the counts in untreated plots ranged between 29 to 224 pusley/m2 and were highe r than in either herbicide plot which ranged between 4 to 79 pusley/m2 (Figure 1-8). There were no significant differences in pusley counts between areas treated with glyphosate or glyphosate tank-mixed with halosulfuron. There were significant differences in pus ley counts between cultivation methods. After the first fallow treatments were applied pusley coun ts were higher in the cultivated plots (205 pusley/m2) than in the non-cultivated plots (84 pusely/m2) (Figure 1-9). Although, tillage killed the majority of the existing pusley plants, it stim ulated a flush of pusley seeds within the soil to germinate in synchronization. However, after the third fallow treatment the non-cultivated areas had significantly higher pusley coun ts. Therefore, it appears tillag e over time gradually depletes the soil seed bank reserves and limits the seed rain being deposited within the soil. The pusley counts in the uncultivated plots were 162 pusley/m2, compared to the cultivated plots which had an average of 91 pusley/m2. Crabgrass fallow Initially crabgrass was uniform ly distributed throughout the field. However, after the first fallow treatments were applied, all methods dr astically lowered the crabgrass infestation compared to the untreated control (Figure 1-10). The interaction in crabgrass counts was signi ficant between cultivation and herbicides. The amount of crabgrass reduction (> 86 %) was significant compared to the untreated control

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77 (74 crabgrass/m2), after just one fallow applic ation (Figure 1-11). Gl yphosate tank mixed with halosulfuron without cultivating (2 crabgrass/m2) controlled crabgrass better than the herbicide combination plus tillage (11 crabgrass/m2) and cu ltivation alone (9 crabgrass/m2). Furthermore, spraying glyphosate without cultivating (3 crabgr ass/m2) reduced crabgrass to a greater extent than spraying with glyphosate plus halosulfur on with cultivation (11 crabgrass/m2). Although tillage controlled the existing crabgrass populati on, it stimulated new crabgrass seedlings to germinate. On the other hand, herbicides cont rolled emerged crabgrass but did not disturb the soil and cause seedling germinati on. Halosulfuron does not contro l grasses, therefore it was not expected to increase the efficacy of glyphosate. Similarly, there were significant differences between treatments at the beginning and after the first fallow application of the second year. There was long term carry over control from the previous years fallow treatments at the beginning of the second year. Cultivating alone (5 crabgrass/m2) and all the herbicide treatments (1.75-2.25 crabgrass/m2) ex cept halosulfuron tank mixed with glyphosate without culti vation (9 crabgrass/m2) reduced crabgrass counts compared to the untreated control (11 crabgrass/m2). After the first round of herbicides were applie d the second year the untreated check had the highest crabgrass densities (20 crabgrass/m2), followed by the cultivation check (9 crabgrass/m2) and then all fallow ing techniques that utilized herb icides (0-0.75 crabgrass/m2). In general cultivation provided better crabgrass c ontrol than non cultivation fallowing regiments. In addition, fallowing using glyphosate or glyph osate plus halosulfuron reduced crabgrass infestation better than non-herbicide programs. Cultivation and the herbicides killed adult crabgrass, which prevented seed production and caused a decline in the population. As expected, halosulfuron did not increase the efficacy of glyphosate.

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78 Hairy indigo fallow There was a separation in hair y indigo counts between the unt reated, cultivation alone and herbicide plots (Figure 1-12).The untreated plot s contain the highest num ber of hairy indigo, the cultivation check plots have a m oderate amount of hairy indigo and the plots treated with either glyphosate by itself or tank mixed with halosulf uron had the lowest density of hairy indigo. Glyphosate alone or tank mixed wi th halosulfuron consistently pr ovided excellent control of hairy indigo. Although cultivation controlled adul t hairy indigo plants, it could have induced germination by scarifying the hard seed coat, allowing the seed to imbibe water and break physical dormancy. There was a significant differen ce in hairy indigo counts between herbicide treated plots. After the second fallow treatments were app lied until the end of the fallow period, the nonherbicide treated plots contained more hairy indigo (21to 24 hair y indigo/2) than the herbicide treated plots (0 to 11 hairy indigo/m2) (Figure 1-13). Browntop millet fallow The cultivation without herbicide plots cons istently had a greater num ber of browntop millet compared to the infestation found in all the other treated plots and the untreated check (Figure 1-14). A likely explanation, is that tillage scarified the seed husk surrounding the browntop millet seed, releas ed the seeds from dormancy, and promoted germination. In the beginning of the second year there was an interaction between cultivation and herbicides. The cultivated check contained mo re browntop millet (20 browntop millet/m2) than the other fallow treatment plots (< 2.25) (Figure 1-15). In ad dition, there were significant differences in browntop millet counts between herbicide and non herbicide plots. At the beginning and end of the second year of fallo wing, both herbicides reduced browntop millet counts (0-1.25 browntop millet/m2) compared to non herbicide plots (6-11 browntop millet/m2)

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79 (Figure 1-16). Glyphosate provided excellent po st emergent control of browntop millet. The addition of halosulfuron was not expected to increase the pre emergent control of browntop millet. Smallflower morningglory (data not shown) There is no consistent pattern of control for sm allflower morningglory over time using any of the fallow treatments tested, except for gl yphosate with cultivati on which gave fairly consistent morningglory control during the fallow period. There we re no significant differences in smallflower morningglory counts due to a ny fallow treatments or factors implemented. Although the herbicides did not kill all the smallflower morningglor y plants, they caused severe damage and prevented the plants from growi ng, flowering, and producing seeds normally. In this manner, glyphosate may lower the amount of smallflower morningglory present in the field over a long period of time. This same trend was observed by Sharma and Singh (2007) when applying glyphosate to ivyleaf morningglory. They f ound that ivyleaf morningglory fl owering was inhibited by an application of glyphosate at 2.5 kg/hg. In addition, glyphosate altered the plant architecture of ivyleaf morningglory, causing the loss of apical dominance and pr oduction of lateral branches. In their study, glyphosate reduced the biomass of ivyleaf morningglory by 14-24%. According to their study, glyphosate efficacy to kill ivy leaf morning glory was dependent on the age of the plant. Glyphosate applied at a rate of 1.25kg/ha to 3-week old plants provided 44% control of ivyleaf morningglory. As ivy l eaf morningglory plant age increas ed, percent control decreased. This difference in ivyleaf morni ngglory control was significant be tween applications made to 3week old plants and 7-week old plants.

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80 Carpetweed fallow There was an overall pattern where carpetweed n umbers were greatest in the cultivation check plots and the glyphosate followed by cultiva tion plots (Figure 1-17). According to the analysis of variance there was an interaction in carpetweed counts between herbicides and cultivation. Following the first herbicide application and t illage during the second fallowing season, all methods (0.5 to 2.75 carpetweed/m2) reduced carpet weed counts more than the cultivated check (13 carpetweed/m2) and glyphosate followed by cult ivation (12 carpetweed/m2) (Figure 1-18). Cultivation increased carpetweed numbers. Alth ough glyphosate killed the carpetweed that was present when it was applied it did not provide residual preferment control after the soil was tilled. However, the addition of halosulfur on provided residual preferment control of carpetweed, thus counts were lo wer even after tillage. After the last fallow herbicid e applications were made th e untreated (2.75 carpetweed/m2) and all herbicides (0 to 3.25 carpetweed/m2) re duced carpetweed better than cultivation alone (17 carpetweed/m2). As mentioned earlier, glyphosate and glyphosate plus halosulfuron provided excellent control of carpetweed. In addition, cultivation incr eased carpetweed counts by causing an immense flush of seedling germination. Redweed fallow (data not shown) Redweed was a m ajor weed in Live Oak. No differences were found in redweed counts between treatments. Although ther e was no statistical difference in redweed numbers, there were notable observations in the plant morphology betw een herbicide and non-herbicide treated plots. In the untreated plots, redweed was allowed to develop, flower, and produce seeds normally. The herbicides did not kill redw eed, which would explain why there was no difference in weed counts. However, the herbicides caused stunt ing, shortened nodes and sprouting. Although the

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81 herbicides did not kill redweed, they prevented the treated plan ts from growing normally and producing seeds during the fallow period. Other minor weeds (data not shown) There were other m inor weeds, which were sp arsely distributed throughout the field during the fallow period. These weeds were not prevalen t in every plot and of tentimes not even an individual could be found in ev ery replication. However, berm udagrass (located primarily along the outside boarders), goosegrass, sicklepod, southern sandbur, crowfootgrass, and pink purslane counts were taken when observed. Due to the inc onsistent distribution and lack of prevalence no results could be fairly derived for these weeds. Crop Data Purple nutsedge in peppers year 1 Purple nutsedge that penetrated through th e plastic m ulch during the cropping season was highest in the cultivated check plots, followed by the untreated plots, and the plots treated with herbicides had the least amount of purple nutsedge (Figure 1-19) Therefore, purple nutsedge infestation distribution during the first year of cropping was consis tent with the results found for the fallow period. Sedges are known for their ab ility to penetrate through plastic mulch (and other physical barriers) due to th eir sharp leaf tips th at cut through the mulch. In addition, their underground tuber reserves provide a carbohydrate source that allows the sedge to germinate and continue to grow for a relatively long period of time without s unlight before becoming depleted, compared to most seeds (especially small seed ed species). Purple nutsedge continued to proliferate throughout the growing season, especially in the cultiv ated check (increased from 15 to 54 nutsedge /30 LBF) and untreated plots (inc reased from 6 to 17 nutsedge/30 LBF). These findings were typically of what might be expected in a spring crop, since temperatures began to

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82 get warmer throughout the season. Besides temperature, irrigation and fertilizers were applied during the crop, which were also benefici al to the growth of purple nutsedge. In addition, herbicides significantly influenced purple nutsedge counts in bell peppers during the first cropping season. Glyphosate (0.9 to 4 nutsedge/30 LBF) a nd glyphosate tank mixed with halosulfuron (0.8 to 2.9 nutsedge/LBF) treated plots containe d less purple nutsedge than non-herbicide treated plots (10 to 35.6 nutsedge/30 LBF). These findings are also consistent with the results obtained for purpl e nutsedge during the fallow period. Weeds in pepper rows year 1 There were m any weeds other than purple nu tsedge present within the rows of pepper during the first year. Unlike purple nutsedge, these weeds did not puncture the plastic mulch themselves, but instead grew through the holes punc hed in the mulch for the pepper transplants. Most weeds, besides sedges, are not able to ge rminate and penetrate th rough the black plastic mulch because it physically restricts light penetrat ion (required to stimulate seed germination in certain species) and as a mechanical barrier to prevent weed emergence. Many times weeds germinate underneath the mulch and die due to the lack of light. Carpetweed, coreopsis, large crabgrass, hairy indigo, pink pur slane, cutleaf evening primro se, Florida pusley, redweed, and smallflower morningglory were observed growing through the planting holes. There was not a significant inte raction in weed counts for an y species between cultivation and herbicides in bell peppers rows. However th e main effect of herbicide was significant for pusley and crabgrass counts. In addition, the main effect of cultivation was significant on crabgrass counts. Pusley counts were higher in plots that were not treated with herbicides (104.5 pusley/ 30LBF) compared to plots treated with either glyphosate or glyphosate plus halosulfuron, 37 and 35 pusley/30 LBF, respectfully (Figure 1-21). There was not a difference in pusley counts

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83 between the glyphosate and glyphosate tank mixed with halosulfuron plots. In addition to post emergent control of pusley, halosulfuron was supposed to provide a dditional pre emergence control of pusley, however the adde d halosulfuron did not increase cont rol of pusley as expected. Similarly to pusley, crabgrass counts were lower in plots treated with either glyphosate (1.4 crabgrass/30 LBF) or glyphosate tank mixed with halosulfuron (1.3 crabgrass/30 LBF) compared to the plots not treated with herbicid es (4 crabgrass/30 LBF) (Figure 1-22). Crabgrass counts were also lower in cult ivated plots (1.25 crabgrass/30 LB F) compared to uncultivated plots (3.25 crabgrass/30 LBF) (Figure 1-23). Weeds in pepper row middle year 1 There were various sp ecies of weeds present in the pepper row middles during year 1. These weed include carpetweed, large crabgrass, hairy indigo, cutleaf ev ening primrose, purple nutsedge, Florida pusley, redweed, smallflower morningglory, and yellow nutsedge. The density of these weeds were much higher in the row middles compared to the rows, because the row middles were not covered with plastic mulch. There were only two weed species that had significantly lower counts due to the fallow treatments. There was not a si gnificant interacti on in pusley or crabgrass counts between herbicide and cultivation. However, both species counts were significantly different between the main effects of herbicides. This is consistent with the pattern found for these species in the pepper rows. Florida pusley and large crabgrass counts were lower in plots that were treated with herbicides during the fallow than the non-herbic ide plots. The counts for Florida pusley within the plots not treated with herbicide were 462 pus ley/m2 and the counts in the herbicide plots were between 164 and 181 pusley/m2 (Figure 1-24). Crabgrass counts in the row middles that were not sprayed during the fallo w period were 24 crabgrass/m2 and the counts in the herbicide

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84 treated row middles were between 10 and 11 cr abgrass/m2 (Figure 1-25). There was not a difference in Florida pusley or large crabgrass co unts in plots that were treated with glyphosate or glyphosate plus halosulfuron. It was expected that halosulfuron would provide additional control of crabgrass and pusley, how ever this was not the case. Pepper heights year 1 Pepper heig hts were noticeably different betw een treatments from visual observations. Therefore, six pepper heights were measured pe r plot to determine stunting from herbicide carryover. There was not a significant interac tion in pepper heights between cultivation and herbicides, however the main effect of herbicides was significant. The plants in plots not treated with herbicide (26 cm) were significantly taller than the pepper plants grow n in plots treated with herbicides (21-22 cm) (Figure 1-26). There was not a difference in pepper plant heights in rows that were treated with either herbic ide treatment during the fallow period. This data suggests that the herbicides ma y not have caused stunting, especially since glyphosate is known to be relatively non-toxic to crop plants, especially if the pre-plant interval is adhered to. Rather, it may be possible that the pepper plants in the non-herbicide plots were leggy in response to competing with the othe r weeds for sunlight. Hunt (1988) found that stressed plants from low light conditions usua lly partition resources toward shoot elongation. However, the exact discrepancy in pepper heig hts between herbicide treatments cannot be determined by this experiment. Weeds in beans year 1 Carpetweed, coreopsis, crabgrass, hairy indi go, cutleaf evenin g prim rose, purple nutsedge, Florida pusley, redweed, smallflower morningglor y, and yellow nutsedge were present in the beans during the first cropping season. There were not significant interactions in the % ground cover of all weed species between herbicide and cultivation, however the main effect of

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85 herbicide was significant in regards to % cover. The overall infestation of all weeds combined was significantly different between fallow herbic ide treatment plots (Figure 1-27). The percent ground cover of all weeds was highest in the bean rows that were not treated with herbicides (90%) during the fallow period. Percent cove r was not significantly different between glyphosate (53%) and glyphosate plus halosulfuron treated plots (55%). These results are reasonable, since a large portion of the weeds comp rising the total weed c over were significantly different between herbicide treatments includi ng purple nutsedge, pusley (primary species present in field), and crabgrass. Analysis of variance indicated that there was not a significant interaction in purple nutsedge counts between herbicid e and cultivation, however the herbicide main effect was significant. Unlike in the peppers, cultivation did not play an effect in purple nutsedge counts in the beans during the first cropping season. A possi ble explanation, is that there was competition from other weeds present in the beans. Sin ce it is grown on bare ground without mulch, purple nutsedge was not allowed to prol iferate in the same manner that was observed in the peppers on mulched beds with a drastically lower am ount of competition from other weeds. As stated, there was a significant difference in purple nutsedge counts in the bean rows between herbicide treatments during the first cropping season (Figure 1-28). Purple nutsedge densities were highest in the bean plots that we re not treated with herb icides (29 nutsedge/m2) during the previous fallow period. There was no significant difference in purple nutsedge counts between the herbicide treatments (0-0.5 nutsedge/m2). Purple nut sedge was virtually eradicated in the bean plots that we re treated with either herbicide trea tment. As discussed earlier, there was a lot of interspecific competition with nutsedge in the beans during the first year. This was largely due to the ineffectiveness of the pre-plan t herbicide applied prior to planting which would

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86 typically control most of the w eeds present in the field, except for purple nutsedge and sexually propagated weeds with hard seed coats. It is theorized that s-metolachlor did not provide adequate control of several weed species because there was a l ack of adequate soil moisture present at the time of ap plication. S-metolachlor and most other pre plant herbicides require enough soil moisture to move the pre plant herbicid e into the soil where it controls the imbibing and germinating seeds. If supplemental irrigation had been provided, greater control of certain weeds would have been expected. There was disfiguration and herbicide symptomology (more spindly plants with thinner, ye llower leaves) observed in many of the weeds (especially Florida pusley), however the pre-plant application di d not result in plant death as expected. There was not a significant interaction in Florida pusley counts between herbicides and cultivation, but the main effect of herbicide was significant. Florida pusley densities were significantly higher in plots that were not treated with herbic ides during the summer before planting (388 pusley/m2) (Figure 1-29). Pusley counts were not significantly different between plots treated with glyphosate or glyphosate tank mixed togeth er with halosulfuron, 96 and 83 pusley/m2 respectfully. It was expected that cu ltivation and the additi on of halosulfuron would provide superior control of pusley. The amount of pusley present in the field would have been reduced with a proper application of s-metol achlor under ideal environmental conditions. This same pattern was recognized with crabgra ss counts in the bean rows. There was not a significant interaction in crabgr ass counts between herbicides and cultivation (at the alpha = .05 level), but the main effects of both herbicides and cultivation wa s significant. The plots that were not treated with herbicides had a si gnificantly higher number of crabgrass (16 crabgrass/m2) than the herbicide plots and ther e was no difference between herbicide plots (3-6 crabgrass/m2)(Figure 1-30). However, numerically crabgrass numbers were lowest in the plots

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87 treated with both glyphosate and halosulfuron. In addition, crabgrass dens ities were significantly greater in plots that were not cultivated (13 crabgrass/m2) during the previous fallowing period, when compared to the cultivated plots 3 cra bgrass/m2) (Figure 1-31). Although, the pre plant application was not effective at controlling weeds that are typical ly controlled by s-metolachlor, this highlighted the sole effect of the fallow tr eatments on weed control and made their effect more pronounced, which is important to understand, especially in minor vegetable crops which have no labeled pre-plant herbicides. Crop yields year 1 (data not shown) There were not any significan t inte ractions in pepper yi elds between herbicide and cultivation. In addition, the main effect of herbicide or cultiv ation on pepper yields were not significant. Unfortunately there were no significant differences in pepper yields for the first harvest, the second harvest or th e total marketable fruit yield. In our experiment the use of cultivation, glyphosate, glyphosate ta nk-mixed with halosulfuron or co mbinations of these fallow techniques did not improve pepper yields signif icantly. However, there was great variability between replications which was mainly attributed to deer damage. Furthermore, we were not able to mechanically harvest the snap bean s the first cropping season due to the heavy impenetrable weed densities present in the field. Green beans are typically harvested by machine in Florida, therefore if the beans could not be harv ested mechanically it is not practical to harvest them by hand, since it will not be applied by farmers. Purple nutsedge within the pepper row year 2 There were three different preplant herbicides included in th e second year experim ent to determine which combination of fallow treatment and pre-plant herbicide treatment most effectively controlled specific weed species in peppers.

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88 The results of the study were different in the second year comp ared to the first. During the second year, the untreated contro l consistently had th e highest number of purple nutsedge over three sampling dates (> 86 purple nutsedge/30 LBF), fo llowed by the cultivated check (> 39 purple nutsedge/30 LBF), and than the herbicide treatments (> 13 purple nutsedge/m2) (Figure 132). When left untreated, purple nutsedge numbe rs increase initially and then decrease during the fall growing season. The increase and declin e in nutsedge population ca n be explained by the weather conditions. During the summer, nutsedge increased due to the warm, wet growing conditions needed for nutsedge to grow and proliferate. But, during the fall, temperatures and rainfall decreased and purple nutsedge is known to decline in numbers and enter dormancy under these unfavorable growing conditions. It appears that after two years of summer fallowing, cult ivation began to control purple nutsedge compared to the untreated control. Th erefore, tillage holds a possibility of providing nutsedge control if a long term approach is adop ted. In addition, the first crop was planted in the spring and the long period of inactivity may have cau sed nutsedge in the til led plots to establish, proliferate, and continue to pr opagate. During the second year, there was a quick succession of cultivation events and the entire field was cultivated prior to be d preparation and planting. Thus, purple nutsedge in the cultivated plots may not have had time to establish between tillage events and this caused tuber desiccation, carbohydrate depletion, and death. In addition, the cultivation before planting may have caused an increase in purp le nutsedge counts in th e untreated plots that was not apparent during the fallow season, because apical dormancy was released. The effects of herbicides were significant fo r purple nutsedge counts during the second bell pepper crop. Herbicides lowere d purple nutsedge dramatically (< 10 purple nutsedge/30 LBF)

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89 compared to no herbicides (> 62.5 purple nutsedge/30 LBF) (Figure 1-33). This was similar to the trends observed in purple nuts edge during the first growing season. EPTC was expected to provide control of purple nutsedge since pr evious studies have revealed that EPTC applied under the plastic in tomatoes was shown to be effective at controlling purple nutsedge (M cAvoy and Stall, 2008; Santos 2009), however the irrigation methods differed between these experiments and ours. In the first study seepage irrigation was used, thus water was being pushed up to the soil surface from below, this provided adequate soil moisture to the herbicide without causing it to leach through the soil surface. In the second study (which was being conducted simultaneously with our experiment), EPTC was applied either sprayed on the soil surface underneath the plastic or applied through drip irrigation. Santos (2009) found that excessive irrigation from drip applications caused EPTC to be washed down into the soil profile which caused it to be ine ffective at controlling nuts edge sprouting (because most nutsedge tubers are near the soil surface) an d caused toxicity to tomato plants when they grew bigger and their roots penetrat ed the contaminated zone in the soil. Therefore, it can be concluded that EPTC may have been effective at controlling purple nutsedge if the proper amount of drip irrigation was provided. Basically enough irrigation to keep the soil moist without causing leaching of the chemicals. There were weeds that began to emerge through the planting holes during the second pepper crop, however an early frost prevented th e identification and data collection of these weeds. Cabbage weeds year 2 There were m any weeds present in the cabba ge crop that was grown during the second year of the study. In addition to many of th e weeds present during the spring crop, there were also several winter annuals in the fall/winter cr op that were not observe d during the first crop or

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90 the summer fallow period. The weed population c onsisted of purple nutsedge, pusley, crabgrass, smallflower morningglory, cutleaf evening primro se, wild mustard, and coreopsis. However, wild mustard and coreopsis were not prevalent in all areas of the field. There was a significant interac tion in purple nutsedge counts between fallow herbicides and cultivation techniques. Purple nutsedge control in the cabbage crop was lowest in the untreated fallow plots, moderate in the cultivat ed check plots (53% cont rol) and highest in the remaining plots (> 94% control) (Figure 1-34) The level of purple nu tsedge control provided by the various fallow treatments in cabbage was si milar to the level of purple nutsedge control found in the peppers. There were no interactions in smallflower morningglory percent control ratings between herbicide, cultivation and pre plant herbicides or any combinations of the three. However, the main effect of pre plant herbicides was signifi cant. There was a significant difference in the smallflower morningglory control between pre-pl ant herbicide treatments within the cabbage rows. The rows treated with oxyfluorfen resu lted in the highest level of smallflower morningglory control (95% cont rol) (Figure 1-35). S-meto lachlor controlled smallflower morningglory better (76% control) than the unt reated control but si gnificantly less than oxyfluorfen (95% control). Florida pusley and large crabgrass control ratings in the cabbage crop did not have significant interactions between fallow herbicid es, fallow cultivation and pre plant herbicides. However, there were significant interactions in both weed control ratings between cultivation and pre plant herbicide. Theref ore, significant Florida pusley a nd crabgrass control was obtained within the cabbage crop. Control of Flor ida pusley and crabgrass was dependent on the combined effect of fallow cultivation and pre pl ant herbicide application when transplanting.

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91 Oxyfluorfen applied to either cul tivated or uncultivated fallow plot s provided the best control of Florida pusley (above 95% control) (Figure 1-36). S-metolachlor provided better Florida pusley control in plots that were cult ivated during the fallow period ( 61% control) compared to plots that were not cultivated (40 % control). S-metolachlor did not contro l (40 to 61 % control) Florida pusley as well as oxyfluorfe n (95 to 98% control). Plots th at were not treated with a pre plant herbicide had the poorest Florida pusley co ntrol, regardless of cu ltivation practice during the fallow period. Thus the main factor that contributed to pusley control in the cabbage crop was the pre plant herbicide in which oxyfluorfen controlled pusley better than s-metolachlor. Since pusley infestation occurs fr om seeds within the soil it w ould make sense that a pre plant herbicide to kill germinating se eds would be necessary to prevent establishment in a cropping situation. However, cultivation controlled pusley bette r than no cultivation. These results can be explained by the fact that alt hough cultivation and herbicides both controlled pusley in the fallow period, and thus subsequently prevented the weed s from flowering and setting seeds. In addition to preventing seed rain it was apparent th at tillage may have in some cases reduced the number of viable seeds in the soil seed bank by stimulating germination and by seed burial. Lastly, fallow cultivation may have broken up the crop residues and clumps in the soil thus providing a fluffy soil with good ti lth that would provide a greater surface contact for the pre plant herbicides when applying and greater pr e plant herbicide movement within the soil. The control of crabgrass was highest in the plots that were trea ted with oxyfluorfen whether cultivation was performe d during the summer or not (99% control) and in plots that were cultivated during the summer than treated with s-metolachlor after planting (94% control) (Figure 1-37). S-metolachlor did not control crabgrass as well when cultivation was not implemented during the fallow period (83% control). Plots that were not treated with a pre plant

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92 herbicide resulted in the lowest control of crabgr ass even if the plot was cultivated during the fallow period. Crabgrass and pusley had a similar response to the effect of cultivation and pre plant herbicides. The same factors that affected the pusley control level would likely explain the control realized in large crabgrass. Thes e weeds may have responded similarly due to similarities between the two species. Both pl ants reproduce primarily by seed, both are summer annuals, and both produce a small seed that does no t remain dormant in the soil for long periods of time. There was no interaction in cutleaf eveningpr imrose control between fallow herbicide, fallow cultivation, and pre plant herbicide. Ho wever, there was a sign ificant interaction in cutleaf evening primrose control between fallow he rbicides and pre plant he rbicides. The control of cutleaf evening primrose was significantly different in the pl ots between the combinations of fallow herbicides and pre plant herbicides. Cutl eaf evening primrose was controlled best in all the plots that were treated with oxyfluorfen prior to transplanting no matter what fallow herbicide was applied (> 94% control)(Figure 1-38). The application of s-metolachlor did not control cutleaf evening primrose (26 to 54 % co ntrol) as well as oxyfluorfen applications. Smetolachlor provided better contro l of cutleaf evening primrose in plots that were not treated with herbicide during the fallow period (54% cont rol) and in plots that were treated with glyphosate tank mixed with halosulfuron (49% cont rol). The application of s-metolachlor in plots that were treated with glyphosate when fallowing resulted in decreased cutleaf evening primrose control (26% control). The control of cutleaf evening primrose was poorest in plots that were not treated with a pre plant herbicide, despite the fallow herbicide treatment that was used. In summary, oxyfluorfen controlled cutleaf evening primrose better than s-metolachlor, and s-metolachlor controlled cutleaf eveningprimrose better than no pre plant herbicide. It is

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93 uncertain why glyphosate applied during the fallow hindered the effect of a pre-plant application of s-metolachlor on cutleaf even ingprimrose control during the growing season. However, the level of reduction was significant. The expe riment should be replicated to verify the reproducibility of these results. Bean weeds year 2 The weeds within th e beans included: purple nutsedge, pusle y, crabgrass, smallflower morningglory, cutleaf evening primrose, wild mu stard, and coreopsis. However, wild mustard and coreopsis were not uniformly distributed within the experimental area. As explained earlier, several of these winter annuals such as cutleaf evening primro se, wild mustard and coreopsis were not present during the summer fallow period and were not as prevalent during the spring crop. Therefore, it would be assumed that su mmer fallow techniques would not control winter annuals. There were not any significan t interactions in weed control between fallow herbicide, fallow cultivation and pre plant herbicides for any of the weeds in the field. However, there was an interaction in pusley control between fallow herbicide and pre plant herbicide, and fallow cultivation and pre plant herbicide. In addition, the main effect of pre plant herbicides were significant for the control of large crabgra ss, cutleaf eveningprim rose, and smallflower morningglory. The main effect of fallow herbic ides was significant for controlling smallflower morningglory and purple nutsedge. There were significant differences in the contro l of crabgrass, cutleaf eveningprimrose and smallflower morningglory between pre plant he rbicides. S-metolachlor and pendimethalin provided the best control (> 98% control) of crabgrass in be ans (Figure 1-39). EPTC gave good control of crabgrass (90% contro l) and no pre plant he rbicide resulted in the poorest crabgrass control.

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94 The application of s-metolachlor provided th e highest level of cutleaf evening primrose control (89%) (Figure 1-40). EPTC controlled cutleaf eveningprimro se (56% contro l) better than pendimethalin (34% control) and the untreated check. All pre plant herbicides provided better control of smallflower morningglory (> 83% control) than the untreated ch eck (Figure 1-41). These result s indicate that although fallow cultivation and herbicides may control these weeds during the summer, a pre plant herbicide should still be used to prevent weed infestation during the crop. There are a large amount of viable seeds within the soil seedbank that rema in dormant until there are favorable conditions for them to grow. This is especially true for rudi mentary species in disturbed soil surfaces such as those encountered in conventional cropping systems. There was also a significant difference in th e level of smallflower morningglory control between fallow herbicides. Glyphosate plus halo sulfuron applications re sulted in better control of smallflower morningglory (75% control) than the untreated check (55% control) but provided similar levels of control as glyphosate by itself (67% cont rol) (Figure 1-42). Fallow applications of glyphosate provided similar levels of control (67% control) as the untreated herbicide check (55% control) and glyphosate tank mixed with halosulfuron (75% control). A possible explanation is that is that the halosulfur on provided additional pre emergent control of smallflower morningglory during the fallow peri od and therefore reduced the population during the crop. Significant differences in pusley control we re found between fallow herbicide/pre plant herbicide combinations and between fallow cultivation/pre plant herbicide combinations. In regards to the fallow herbicide/pre plant herbic ide control of pusley, fa llow without herbicide followed by s-metolachlor (97% control), no herbic ide followed by pendimethalin (99% control),

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95 glyphosate followed by s-metolachlor (98% c ontrol), glyphosate followed by pendimethalin (99.6% control), glyphosate tank mixed with halo sulfuron followed by EPTC (96% control), glyphosate tank mixed with halosulfuron follo wed by s-metolachlor (99% control) and glyphosate tank mixed with halosulfuron followed by pendimethalin (100% control) gave the best control (Figure 1-43). Glyphosate followed by EPTC (93% control) did not control Florida pusley as well as glyphosate followed by pendimethalin (99.6% control) and halosulfuron tank mixed with glyphosate followed by pendimethalin ( 100% control). All pl ots where a pre plant herbicide was not applied had the most severe pusl ey infestation. It appears that EPTC did not control pusley as well as the othe r herbicides especially when th ere were no herbicides applied during the fallow. Overall all pre plant herbicides controlled pusley better than the untreated pre plant scenario. These results indicate that smetolachlor or pendimethalin (numerically better control) should be used to contro l pusley in beans. However, if EPTC is used as a pre plant than it would be advantageous to used with fallow he rbicides, specifically glyphosate tank mixed with halosulfuron during the fallow season. In regards to the fallow cultivation/pre plant herbicide control of pusley, s-metolachlor and pendimethalin with or without cultivation resulted in the hi ghest level of pusley control (> 98% control) (Figure 1-44). EPTC in combination with fallow cultivation gave better control of pusley (93% control) than without fallow cultivation (84% control). All plots that were not treated with pre plant herbicides had the most pusley regardless of fallow cultivation technique. Therefore, it would be recommended that s-metolach lor be applied pre plant in beans to control pusley. However, if EPTC was being used it wo uld be better to cultivate rather than not cultivate. These results suggest that excellent pusley control can be obtained with the proper pre

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96 plant herbicides, however if suboptimal pre plant he rbicides were used it would be beneficial to apply fallow herbicides or till during the fallo w period to achieve be tter pusley control. There was a significant difference in purple nu tsedge control between fallow herbicide treatments in the bean crop of the second year. Both glyphosate and gly phosate tank-mixed with halosulfuron (> 95% control) provided better control of purple nutsedge than the untreated herbicide areas (6% control) (Figure 1-45). Thes e results are consistent with the findings we found for purple nutsedge in the fallow period, in the first bean crop, and in the peppers. This shows that systemic post emergent herbicides (glyphosate and glyphosat e plus halosulfuron) greatly increased the level of pur ple nutsedge control compared to not utilizing herbicides during the fallow period. The explanation for these findings were stated earlier in the fallow section. Pepper and bean dry weights year 2 (data not shown) There were no significant interactions in pe pper or bean plant dry weights between f allow cultivation, fallow herbicides, and pre plant herbicides or any comb ination of these factors. In addition the main effects of fallow cultivation, fallow herbicides, or pre plant herbicides did not significantly affect pepper or green bean plant dry weights. There were no significant differences in bell pepper or green bean pl ant dry weights between fallow tillage, fallow herbicide and pre plant herbicide treatments or the various combinations of the three (data not shown). No fruit yield was obtained from either crop due to an untimely frost event. The peppers were at first flower gr owth stage and the beans had be gun to flower when they were frozen to the ground. In addition, the weeds were very small when the frost occurred. Since the crops were at a uniform growth stage and the we eds were very small during the frost event there were not any significant differences in weight s because the weeds did not compete long enough with the crop to hinder growth, and development. One would speculate that if the weeds were

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97 allowed to compete with the crop all season long there may have b een differences in crop yields since there were differences in weed control between the various fallow and pre-plant treatments. Cabbage yield year 2 There were not any significan t inte ractions in cabbage numbers, cabbage weight, or average cabbage head weight between fallow herbicide, fallow tillage, and pre plant herbicides or any combination of these factors. However, pre plant herbicides main effects significantly impacted cabbage yields. There were significant differences in the number of cabbage per plot, the total cabbage yield per plot, and the average cabbage weight between the plots treated with pre-plant herbicides. The plot s treated with oxyfluorfen produced the highest number of cabbage per plot (13 cabbage/15 LBF) (Fi gure 1-46). There were less cabba ge plants in the plots that were not treated with a pre pl ant herbicide (11.5 cabbage/15 LBF) There was no difference in the number of cabbage in the plots treated wi th s-metolachlor (12.7 cabbage/15 LBF) when compared to the untreated (11.5 cabbage/15 LBF) or the oxyfluorfen treated plots (13 cabbage/15 LBF). The total cabbage yield was highe st in the plots treated with oxyfluorfen pre transplant (40 lbs/15 LBF) (Figure 1-47). S-metolachlor treate d plots had yields (32 lbs/15 LBF) higher than the untreated plots (28 lbs/15 LBF) but not as high as the oxyfluorfen treated areas (40 lbs/15 LBF). The plots that were not tr eated with a pre plant herbicide had the lowest cabbage yield (28 lbs/30 LBF). The average weight per cabbage was highest in the plots treated with oxyfluorfen (3.1 lbs) (Figure 1-48). The rows treated with s-metolachlor and the row not treated with a pre plant herbicide had similar sized cabbages on average (between 2.4 to 2.6 lbs). Although there were several weeds present at the be ginning of the cabbage crop, most of the weeds died during the frost. As a result of the frost, the primary weed present during most of the cabbage growing

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98 season was cutleaf eveningprimrose. In additi on, cabbage has been proven to be a strong competitor with other winter annuals, such as wi ld mustard during the winter season. Thus the effect of fallow cultivation and herbicides did not have an effect on cabbage yield. However, cabbage yield was strongly correlated to pre plant herbicides which significantly controlled cutleaf eveningprimrose. Conclusions Purple Nutsedge Control Glyphosate by itself or tank m ixed with halosulf uron was the most effective fallow method for controlling purple nutsedge regardless of ti llage regiment. Cultivation increased the amount of purple nutsedge during the fallow period and during the first crop compared to the untreated check. However, after two years of cultivating during the fallow there was less purple nutsedge in the cultivated check plot than in the untreat ed check plot in the second crop. Thus, cultivation may be effective at controlling purple nutsedge if implemented over a long time period. In addition, none of the pre plant herbicides were effective at controlling purple nutsedge in peppers, cabbage, or snap beans. Therefore, fallow applications of glyphosate or glyphosate plus halosulfuron are crucial in controlling purple nutsedge within a crop, since methyl bromide fumigation prior to planting is no longer an option, and the pre plant herbicides tested were not effective at controlli ng purple nutsedge. Yellow Nutsedge Control Yellow nutsedge was controlled by all of the fa llow treatments compared to the untreated check. Therefore, fallow cultivat ion and/or tillage provides adequa te yellow nutsedge control. In addition, yellow nutsedge was practically non-exi stent except in the untreated control plots during the cropping period for both years. The pr e plant herbicides were expected to control

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99 yellow nutsedge, however there were no significant differe nces since the infestation was so low during the cropping season. Florida Pusley Control Florida pusley was controlled by glyphosat e and glyphosate plus halosulfuron, compared to the untreated control during th e fallow period. At first, cult ivation increased the amount of pusley but by the second year cultivation resulted in less pusley compared to not cultivating. To summarize the results of fallow control of Flor ida pusley, cultivation controlled pusley better than the untreated check and the treatments with herbicides controlled pusley better than the cultivated check. During the first spring cr op pusley was controlled better by glyphosate and glyphosate plus halosulfuron than the non herbic ide treatments in pepper beds, pepper row middles and in green bean rows. In the second cropping season fallow cultivation plus pre plant herbicides were significant at controlling pusle y. Oxyfluorfen controlle d pusley better than smetolachlor or no pre plant herb icide with or without cultivat ion. S-metolachlor controlled pusley better with cultivation than without cultivation. In the second crop of snap beans both fallow herbicide plus pre plant herbicide and fallow cultivation plus pre plant herbicide were significant at controlling Florida pusley. Pendi methalin and s-metolachlor controlled Florida pusley the best. The efficacy of EPTC was dependent on fallow herbicide applications. When no fallow herbicides were applied, EPTC did not control pusley as good as pendimethalin and smetolachlor, when glyphosate was applied duri ng the fallow period EPTC provided the same level of pusley control as s-metolachlor but not pendimethalin, and when glyphosate plus halosulfuron was applied during the fallow period all the pre plant herbic ides provided the same level of pusley control. Similarly, pendimethal in and s-metolachlor provided the best pusley control regardless of fallow cultivation technique, however EPTC provided better pusley control when the plots were tilled during the fallow period.

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100 Large Crabgrass Control Crabgrass c ontrol between fallow treatments varied by date. However, it appears that many times, any fallow treatment controlled larg e crabgrass better than the untreated check. Sometimes herbicides provided greater control of crabgrass than the cultivated check and sometimes they did not. In one case (after the first fallow applications were applied) glyphosate plus halosulfuron provided greater control of crabgrass than the cultiv ated check and glyphosate plus halosulfuron with cultivation. During the first crop, fallow applications of both glyphosate and glyphosate plus halosulfuron controlled crab grass better than non-herb icide treatments in pepper row middles. In the first bean crop, both fallow cultivation and fallow herbicide applications were important in controlling crabgrass. Glyphosate and glyphosate plus halosulfuron controlled crabgras s better than the non-herbicide treatments. In addition, fallow cultivation controlled crabgrass better than the non-cultivated plots. During the second year, oxyfluorfen provided excellent control of cra bgrass in cabbage independently of fallow cultivation. But, s-metolachlor controlled crabgr ass better with fallow cultivation compared to no fallow cultivation. In the second bean crop, crabgrass control was dependent on pre plant herbicides. S-metolachlor and pendimethalin c ontrolled crabgrass better than EPTC and the untreated check. Hairy Indigo Control Glyphosate and glyphosate plus halosulfuron co ntrolled hairy indigo better than the nonherbicide treatments during the fallow period. However, hairy indigo control did not differ significantly during the cropping se ason at the 0.05 alpha level, but during the first bean crop hairy indigo counts were significan tly different between treatments at the 0.1 alpha level. During the second crop hairy indigo was not present in the field, this is probably due to unfavorable growing conditions (cool and dry), found in the late fall when we planted.

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101 Browntop Millet Control Browntop millet was con trolled in all the fa llow treatments compared to the cultivated check during the fallow period. Therefore, cult ivating alone increased the amount of browntop millet. In addition, glyphosate and glyphosate tank mixed with halosulfuron consistently controlled browntop millet better than the treatments that did not use herbicides in the fallow period (although the difference was not always significan t). Browntop millet was not a problem during the cropping season, however it is possible that browntop millet was misidentified as crabgrass when it was small. Smallflower Morningglory Control Glyphosate treatm ents controlled smallflowe r morningglory better than non-herbicide treatments during the fallow period. Howe ver, glyphosate plus halosulfuron controlled smallflower morningglory better than the non-he rbicide fallow treatments during the second green bean crop. In cabbage, the pre plant herbicide oxyfluorfen c ontrolled smallflower morningglory better than s-metolachlor. In additi on, all the pre plant herbic ides provided better control of small flower morningglory than the untr eated pre plant check in the second snap bean crop. Carpetweed Control At the end of two years of fallowing, all of the treatm ents controlled carpetweed better than the cultivated check. Ther efore, tillage caused an increa se in the carpetweed population. However, even after cultivation, halosulfuron provided preferment control of carpetweed during the fallow period. Cutleaf Evening Primrose Control Cutleaf eveningprim rose was not represented during the fallow period. However, fallow herbicides along with pre plant he rbicides affected cutleaf evening primrose control in cabbage.

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102 Oxyfluorfen controlled cutleaf ev eningprimrose better than s-metolachlor regardless of fallow herbicide used. In the second snap bean crop cu tleaf evening primrose was controlled best by pre plant applications of s-metolachlor, than EPTC, than pendimethalin, which all controlled cutleaf evening primrose better th an untreated pre plant check. Th erefore, pre plant herbicides are necessary to control cutleaf eveningprimrose since it is not present during the fallow period. Cabbage Yield Cabbage total yield was dictat ed by which pre plant herbicide was used. Applications of oxyfluorfen resulted in the hi ghest cabbage number per plot, average cabbage weight, and cabbage total weight. S-metolachlor resulted in similar cabbage numbers, but did not perform as well at controlling weeds (espec ially cutleaf evening primrose ) as oxyfluorfen, therefore the average cabbage head weight and the total cabbage weight per plot was lower in s-metolachlor treated plots compared to oxyfluorfen treated pl ots. However, s-metolachlor improved cabbage yields compared to the untreate d pre plant herbicide check. In conclusions, neither oxyfluorfen nor s-metolachlor hurt cabbage growth but oxyfluor fen controlled most of the weeds present in the field better.

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103 Figure 1-1. Experimental design of Live Oak, FL experiment during the first year. Plot #: Replication 101106 1 201206 2 301306 3 401406 4 Treatment #: Treatment Received 1 Disk, Untreated 2 Disk, Glyphosate, NIS 3 Disk, Glyphosate + Halosulfuron-methyl, NIS 4 No Disk, Untreated 5 No Disk, Glyphosate, NIS 6 No Disk, Glyphosate + Halosulfuron-methyl, NIS Peppers 1 2 15 ft 306 6 305 2 304 4 303 1 302 5 301 3 106 6 105 5 406 4 405 2 404 6 403 3 402 5 206 6 401 1 205 4 104 4 204 5 103 3 203 1 102 2 202 2 101 1 201 3 60 ft 60 ft 15 ft W E S Peppers 1 2 N Beans 1 2 3 4 Beans 1 2 3 4 Plot # Trt. # Plot # Trt. #

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104 Figure 1-2. Purple nutsedge counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Weed counts include all living plants independent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A pp lication Cultivation Crop 0 10 20 30 40 50 60 70 80 90 100 7/24/069/21/063/30/078/4/078/24/079/14/079/27/07Counts/m2Dates Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

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105 a a a a a a a a b b b b a a b b b b 0 10 20 30 40 50 60 70 7/24/069/21/063/30/078/4/078/24/079/14/07Counts/m2Dates No Herb Gly Gly & Halo Figure 1-3. Effect of herbicides on purple nutsedge counts duri ng the summer 2006 and 2007 fallow period in Live Oak, Fl. Means followed by the same letter within a sampling date are not significantly diffe rent according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants inde pendent of visual health. Note x axis dates are not drawn to scale.

PAGE 106

106 a bc c b cc 0 10 20 30 40 50 60 70 80 90 9/27/07Counts/m2Date Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-4. Effect of treatments on purple nutsedge counts during the summer 2007 fallow period in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Signi ficant Difference test at P = 0.05. Weed counts include all living plants independent of visual health.

PAGE 107

107 Figure 1-5. Yellow nutsedge c ounts during the summer 2006 a nd 2007 fallow period in Live Oak, Fl. Weed counts include all living plants independent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A pp lication Cultivation Crop 0 10 20 30 40 50 60 70 80 7/24/069/21/063/30/078/4/078/24/079/14/079/27/07Counts/m2Dates Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

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108 a b a a a a a a b aa a a a a b aa a a a aa a a a aa a b a a a aa a b a a a aa 0 10 20 30 40 50 60 70 80 7/24/069/21/063/30/078/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-6. Effect of treatment by date interaction on yellow nutsedge counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Note x axis dates are not drawn to scale.

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109 Figure 1-7. Florida pusley counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Weed counts include all living plants i ndependent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A pp lication Cultivation Crop 0 50 100 150 200 250 300 7/24/069/21/063/30/078/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

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110 a a a a a a a a a b b b b b a a b b b b b 0 50 100 150 200 2507/2 4 / 0 6 9 / 21/0 6 3/30/07 8/4/07 8/2 4 / 0 7 9 / 14/07 9/27/07DatesCounts/m2 No Herb Gly Gly + Halo Figure 1-8. Effect of herbicides on Flor ida pusley counts during the summer 2006 and 2007 fallow period. Means followed by the same letter within a sampling date are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include all liv ing plants independent of vi sual health. Note x axis dates are not drawn to scale.

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111 a b a a a a a a a a b a a a 0 50 100 150 200 2507/2 4 /06 9 /2 1/0 6 3 / 30/07 8/4/07 8/24/07 9/1 4 / 0 7 9 / 27/0 7DatesCounts/m2 No Cult Cult Figure 1-9. Effect of cultivation on Flor ida pusley counts during the summer 2006 and 2007 fallow period. Means followed by the same letter within a sampling date are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include all liv ing plants independent of vi sual health. Note x axis dates are not drawn to scale.

PAGE 112

112 Figure 1-10. Large crabgrass counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Weed counts include all living plants independent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A pp lication Cultivation Crop 0 10 20 30 40 50 60 70 80 7/24/069/21/063/30/078/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

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113 b bc a a bc a a c bcd a a c a a c b a a c a a a a aa a a a c cd a a c a a c d a a ab a a 0 10 20 30 40 50 60 70 80 7/24/069/21/063/30/078/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-11. Interaction effect of treatment and date on la rge crabgrass counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Means followed by the same letter within a sampling date are not signifi cantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Note x axis dates are not drawn to scale.

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114 Figure 1-12. Hairy Indigo counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Weed counts include all living plants i ndependent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A p p lication Cultivation Crop 0 5 10 15 20 25 30 35 7/24/069/21/068/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

PAGE 115

115 a a a a a a a a b b b b a a b b b b 0 5 10 15 20 25 7/24/069/21/068/4/078/24/079/14/079/27/07 DatesCounts/m2 No Herb Gly Gly + Halo Figure 1-13. Effect of herb icides on hairy indigo counts during the summer 2006 and 2007 fallow period. Means followed by the same letter within a sampling date are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include all liv ing plants independent of vi sual health. Note x axis dates are not drawn to scale.

PAGE 116

116 Figure 1-14. Browntop Millet counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Weed counts include all living plants independent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A pp lication Cultivation Crop 0.0 5.0 10.0 15.0 20.0 25.0 9/21/068/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

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117 a b b b b b 0 5 10 15 20 25 8/4/07 DateCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-15. Effect of treatment on browntop millet counts duri ng the summer 2006 and 2007 fallow period in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include a ll living plants independe nt of visual health.

PAGE 118

118 a a a a a a b aa b a b a a b 0 2 4 6 8 10 12 9/21/068/4/078/24/079/14/079/27/07 DatesCounts/m2 No Herb Gly Gly + Halo Figure 1-16. Effect of herb icides on browntop millet coun ts during the summer 2006 and 2007 fallow period. Means followed by the same letter within a sampling date are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include all liv ing plants independent of vi sual health. Note x axis dates are not drawn to scale.

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119 Figure 1-17. Carpetweed counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Weed counts include all living plants i ndependent of visual health. Note x axis dates and treatment applications timelines are not drawn to scale. Initial Weed Count Herbicide A pp lication Cultivation Crop 0 2 4 6 8 10 12 14 16 18 7/24/068/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo

PAGE 120

120 a a a a a a a a a b a a a b b a a a bb a a a b b a a a b b 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 7/24/068/4/078/24/079/14/079/27/07 DatesCounts/m2 Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-18. Interaction effect of treatment and date on carp etweed counts during the summer 2006 and 2007 fallow period in Live Oak, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Note x axis dates are not drawn to scale.

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121 0 10 20 30 40 50 60 4/23/20075/2/20075/16/2007Counts/ 30 LBFDates Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-19. Purple nutsedge counts per 30 linear bed feet of row with in a bell pepper crop during the spring of 2007 in Live Oak, Fl. Weed counts includ e all living plants independent of visual health. Note x axis dates are not drawn to scale.

PAGE 122

122 a a a b b b b b b 0 5 10 15 20 25 30 35 40 4/23/20075/2/20075/16/2007 DatesCounts/30LBF No Herb Gly Gly & Halo Figure 1-20. Effect of herbicid es on purple nutsedge counts per 30 linear bed feet within a bell pepper crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter within a sampling date are not signifi cantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Note x axis dates are not drawn to scale.

PAGE 123

123 a b b 0 20 40 60 80 100 120 PusleyCounts/30LBF No Herb Gly Gly & Halo Figure 1-21. Effect of herbicides for Florida pusley counts located in the planting holes per 30 linear bed feet within a bell pepper crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not sign ificantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health.

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124 a b b 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 CrabgrassCounts/30 LBF No Herb Gly Gly & Halo Figure 1-22. Herbicide main eff ect for crabgrass counts per 30 LBF within the rows of a pepper crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Weed counts incl ude all living plants indepe ndent of visual health.

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125 a b 0 0.5 1 1.5 2 2.5 3 3.5 CrabgrassCounts/30 LBF No Cult Cult Figure 1-23. Cultivation main effect for cra bgrass counts per 30 LBF w ithin the rows of a pepper crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Significant Difference test at P = 0.05. Weed count s include all living plants i ndependent of visual health.

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126 a b b 0 50 100 150 200 250 300 350 400 450 500 PusleyCounts/m2 No Herb Gly Gly & Halo Figure 1-24. Herbicide main effect for Florida pusley counts per m2 located within the row middle of a pepper crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health.

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127 a b b 0 5 10 15 20 25 CrabgrassCounts/m2 No Herb Gly Gly & Halo Figure 1-25. Herbicide main effect for large crabgr ass counts per m2 located within the row middle of a bell pepper crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health.

PAGE 128

128 a b b 19 20 21 22 23 24 25 26 27 HeightHeight (cm) No Herb Gly Gly & Halo Figure 1-26. Herbicide main effect for the aver age of six bell pepper heights in cm during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05.

PAGE 129

129 a b b 0 10 20 30 40 50 60 70 80 90 100 % CoverCounts/m2 No Herb Gly Gly & Halo Figure 1-27. Herbicide main ef fect for the overall percentage of ground cover for all weed species combined in a snap bean crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not sign ificantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health.

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130 a b b 0 5 10 15 20 25 30 Purple NutsedgeCounts/m2 No Herb Gly Gly & Halo Figure 1-28. Herbicide main effect for purple nutsedge counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Weed counts incl ude all living plants indepe ndent of visual health.

PAGE 131

131 a b b 0 50 100 150 200 250 300 350 400 450 Florida PusleyCounts/m2 No Herb Gly Gly & Halo Figure 1-29. Herbicide main effect for Florida pusley counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Weed counts incl ude all living plants indepe ndent of visual health.

PAGE 132

132 a b b 0 2 4 6 8 10 12 14 16 18 CrabgrassCounts/m2 No Herb Gly Gly & Halo Figure 1-30. Herbicide main effect for large crabgr ass counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Weed counts incl ude all living plants indepe ndent of visual health.

PAGE 133

133 a b 0 2 4 6 8 10 12 14 CrabgrassCounts/m2 No Cult Cult Figure 1-31. Cultivation main effect for large crabgrass counts per m2 in the row of a snap bean crop during the spring of 2007 in Live Oak, Fl. Means followed by the same letter within are not significantly different acco rding to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plan ts independent of visual health.

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134 0 10 20 30 40 50 60 70 80 90 100 123 DatesCounts/30LBF Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-32. Purple nutsedge counts per 30 linear bed feet of row with in a bell pepper crop during the fall of 2007 in Live Oak, Fl. Weed counts include all living plants independent of visual health. Note x axis sampling dates were not equally spaced in time.

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135 a a a b b b b b b 0 10 20 30 40 50 60 70 80 123 DatesCounts/30 LBF No Herb Gly Gly & Halo Figure 1-33. Effect of herbicid es on purple nutsedge counts per 30 linear bed feet within a bell pepper crop during the fall of 2007 in Live Oak, Fl. Means followed by the same letter within a sampling date are not signifi cantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Note x axis sampling dates were not equally spaced in time.

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136 b a a c a a 0 20 40 60 80 100 120 Purple Nutsedge % Control Cult Cult + Gly Cult + Gly & Halo Untreated No Cult + Gly No Cult + Gly & Halo Figure 1-34. Effect of fallow treatments on the control of purpl e nutsedge in the rows of a cabbage crop during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis, stunting, or death.

PAGE 137

137 c a b 0 10 20 30 40 50 60 70 80 90 100 SFMG% Control Untreated Oxyfluorfen S-metolachlor Figure 1-35. Pre plant herbicide main effect for the control of small flower morningglory in the rows of a cabbage crop during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

PAGE 138

138 d a b d a c 0 20 40 60 80 100 120 Pusley% Control cult + untreated cult + oxy cult + s-met no cult +unteated no cult + oxy no cult + s-met Figure 1-36. Interaction effect of cultivation a nd pre plant herbicides on the control of Florida pusley in the rows of a cabbage crop during th e fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

PAGE 139

139 c a a c a b 0 20 40 60 80 100 120 Crab % Control cult + untreated cult + oxy cult + s-met no cult +unteated no cult + oxy no cult + s-met Figure 1-37. Interaction effect of cultivation a nd pre plant herbicides on the control of large crabgrass in the rows of a cabbage crop during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

PAGE 140

140 d a b d a c d a b 0 20 40 60 80 100 120 Cutleaf Evening Primrose% Control no herb + untreated no herb + oxy no herb + s-met gly + untreated gly + oxy gly + s-met gly & halo + untreated gly & halo + oxy gly & halo + s-met Figure 1-38. Interaction effect of fallow herbicides and pre plan t herbicides on the control of cutleaf evening primrose in the rows of a cabbage crop dur ing the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

PAGE 141

141 c b a a 0 20 40 60 80 100 120 Preplant% Control untreated EPTC s-met pendimeth Figure 1-39. Main effect of pre plant herbicides on the control of large crabgrass in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, ne crosis, stunting, or death.

PAGE 142

142 d b a c 0 10 20 30 40 50 60 70 80 90 100 Preplant% Control untreated EPTC s-met pendimeth Figure 1-40. Main effect of pre plant herbicides on the control of cutleaf evening primrose in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05.

PAGE 143

143 b a a a 0 10 20 30 40 50 60 70 80 90 100 Preplant% Control untreated EPTC s-met pendimeth Figure 1-41. Main effect of pre plant herbicides on the control of smallflower morningglory in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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144 b ab a 0 10 20 30 40 50 60 70 80 Herb% Control untreated gly gly & halo Figure 1-42. Main effect of fallow herbicides on the control of smallflo wer morningglory in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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145 d c ab ab d b ab a d ab ab a 0 20 40 60 80 100 120 Herb*Preplant% Control no herb + untreated no herb + eptc no herb + s-met no herb + pendimeth gly + untreated gly + eptc gly + s-met gly + pendimeth gly & halo + untreated gly & halo + eptc gly & halo + s-met gly & halo + pendimeth Figure 1-43. Interaction effect of fallow herbicides and pre plan t herbicides on the control of Florida pusley in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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146 d b a a d c ab a 0 20 40 60 80 100 120 Cult*Preplant% Control cult + untreated cult + eptc cult + s-met cult + pendimeth no cult + untreated no cult + eptc no cult + s-met no cult + pendimeth Figure 1-44. Interaction effect of cultivation a nd pre plant herbicides on the control of Florida pusley in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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147 b a a 0 20 40 60 80 100 120 Herbicide% Control no herb gly gly & halo Figure 1-45. Main effect of fallow herbicides on the control of purple nutsedge in the rows of snap beans during the fall of 2007 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis stunting, or death.

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148 b a ab 10.5 11 11.5 12 12.5 13 13.5 PreplantNumber/15 LBF untreated oxyfluorfen s-metolachlor Figure 1-46. Main effect of pre plant herbicides on the number of cabbage per plot (15 LBF) during the winter of 2008 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05.

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149 c a b 0 5 10 15 20 25 30 35 40 45 PreplantWeight (lbs)/15 LBF untreated oxyfluorfen s-metolachlor Figure 1-47. Main effect of pre plant herbicides on the total cabba ge weight during the winter of 2008 in Live Oak, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05.

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150 b a b 0 0.5 1 1.5 2 2.5 3 3.5 PreplantWeight (lbs) untreated oxyfluorfen s-metolachlor Figure 1-48. Main effect of pre plant herbicides on the aver age cabbage weight during the winter of 2008 in Live Oak, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05.

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151 CHAPTER 3 FALLOW EXPERIMENT CITRA, FL LOCATION Objective The objective of this experim ent was to inve stigate the efficacy of several herbicides (including pre, post, contact, and systemic mate rials) and cultivation on fallow weed control and subsequent crop yields for several vegetables grown in Florida. In addition, pre-pl ant herbicides within the crop were investigated to determ ine which pre-plant herbicide would be most efficacious in conjunction with fallow treatment s to provide the best weed control and the highest crop yields. Materials and Methods A two year study was conducted at the Plant Science Research and Education Unit in Citra, FL to investigate s everal fallow treatments on weed control. The setup of the experiment was a randomized complete block design. The treatments were applied twice per fallow season for two consecutive years. The fallow treatments included: 1) an untreated check 2) glyphosate followed by glyphosate 3) glyphosate and metol achlor tank-mixed followed by glyphosate 4) glyphosate and trifloxysulfuron ta nk-mixed followed by glyphosate 5) paraquat and metolachlor tank-mixed followed by paraquat 6) paraquat and trifloxysulfuron tank-mixed followed by paraquat 7) paraquat followed by pa raquat and 8) cultivated control. After the first herbicide application the field was left undi sturbed (in order to allow the he rbicides action to take effect and to take weed control ratings and weed counts) before the se cond herbicide applications were made. The treatments were replicated 4 times. Pl ot sizes were strips 5 wide by 30 ft long. The orientation of the length of th e plots ran from east to west.

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152 All herbicides were applied w ith a non-ionic surfactant at a rate of .25 % volume/volume. Glyphosate treatments received the equivalent of 2pt/A using a product that contained 5 pounds per U.S. gallon of glyphosate acid equivalents. Metolachlor treatments were applied at rate of 1.25 pt/A using a product that contained 7.62 pounds of active ingredient per gallon. Trifloxysulfuron was sprayed at a rate of 0.2 oz wt/A from a product that contained 75% active ingredient. Paraquat was applied at a rate of 3 pt/A using a pr oduct that contained 2 pounds of active ingredient per gallon. Fallow Measurements Two m easurements were taken for each treatm ent plot; the percent weed control provided by that fallow method and weed counts for each indi vidual species. Percent control is defined as the amount of control provided by each treatment compared to the untreated check in which no fallow treatments were implemented. Therefore by definition the untreated check provided zero percent control, because there was no weed control improvement. However, 90 percent control means that there is 90 percent less weeds in that particular area compared to the untreated check. In addition to plant death, weed control ratings took into account the physical appearance of the weeds present. Treatments that resulted in chlo rosis, necrosis, and stunt ing of weeds were rated as providing weed control greater than that of the untreated check. Weed counts were taken in a .5 m2 (.5 meters wide by 1 meter long) rectangle constructed of PVC pipe. Counts accounted for all living weeds in the area regardless of their physical condition; therefore weed counts provided in formation only pertaini ng to plant death or reduction in numbers provided by the different fallow treatments. In addition, weed counts provided a base level of weeds present in the untreated check plots on which to compare, contrast, and extrapolate the effect of the % weed contro l ratings for the other fallow treatments. Weed counts were only made during the second fa llow season. During the first fallow season

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153 only the cultivated treatment areas were tille d during the fallow season, however during the second fallow season all the fallow treatment area s were tilled. During the second year the cultivated treatment plots were hand hoed ev ery other week during the cropping season in addition to being cultivated during the summer fallow. Crop 1 Sweet corn was planted during the spring afte r the f irst summer fallow treatments were applied. The entire field was treated with the same pre-emergence herbicide directly after the crop was planted. Row middles in the plots were visually rated for % weed control for each individual weed species. No differences in yiel ds were recorded between fallow treatment plots, therefore yield data was not included. Crop 2 Cabbage was planted during the fall after the second summer fallow treatm ents were applied. The cropping experimental design was a split plot desi gn, where the main fallow plots were split into pre-emergence he rbicide treated subplot s. There were two pre-plant herbicide treatments; oxyfluorfen and s-metolachlor. The oxyfluorfen was applied to the soil surface prior to planting cabbage transplants. S-metolachlor was sprayed directly over the top of freshly planted cabbage transplants. Counts per .5 m2 and % weed control visual ratings were recorded for the primary weed species present within the plots. The cultivated control plots were hand hoed every two weeks, starting two weeks after planting and continuing throughout the rest of the growing season until harvest. A single cabbage harvest was conducted. All cabbage heads larger than a softball were harvested. Cabbage vigor ratings, total yield (lbs) measurements and number of heads per plot were recorded, and average fruit size was calcu lated. Cabbage vigor ratings took into account

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154 the physical appearance of the cabba ge plants due to possible herbicide toxicities from either the fallow or pre-plant herbicides. Post Cabbage Harvest Weed Control Long term differences in weed control between fallow treatment plots were still evident even after the second crop was harvested. Henc e, weed control ratings and weed counts were taken to quantify the level of l ong term weed control provided by the various fallow treatments on specific weed species. Statistical Analysis Weed control ratings, w eed counts, and cabbage harvest yield parameters were analyzed in SAS (Statistical Analysis Software). Statis tical differences between fallow and pre-plant treatment plot measurements were identified us ing ANOVA (analysis of va riance) using the Proc GLM procedure. Once statistical differences we re identified, treatment means were separated using LSD (least signif icant differences). Results and Discussion Fallow Period (Sedges) Effect of different fallow treatments on purple nutsedge control yea r 1 Overall, all herbicide treatments provided better nutsedge control (> 35% control) compared to the untreated check (Figure 2-1). In addition, cultivation increased the level of control compared to the untreated check dependi ng on when it was implemented. After the first treatment applications of the first year, there were significant differen ces in nutsedge control between the different fallow treatment plots (Fig ure 2-2). Nutsedge control was highest in the plots that were treated with tr ifloxysulfuron with either para quat or glyphosate (87.5 and 72.5 % control respectively), cultivation (77.5 % control), and paraquat plus metolachlor (72.5% control). The addition of trifl oxysulfuron and s-metolachlor (to a lesser degree) was expected to

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155 increase purple nutsedge control beyond that pr ovided by glyphosate or paraquat alone. The level of control provided by pa raquat plus trifloxysulfuron (87.5 % control) was higher than glyphosate alone (57.5 % control), glyphosate plus s-metolachlor (55 % control), and paraquat by itself (47.5 % control). Glyphosate and paraquat were not expected to perform as highly as the tank-mixes at controlling purple nutsedge, since the various herbicides in th e tank mix are known to control purple nutsedge and they have different mode s of action. Paraquat al one does not usually provide adequate control of purple nutsedge, becaus e it is a contact materi al that causes burning of the foliage but does not translocate within the plant to systemica lly control the underground rhizomes and tubers. Paraquat does not control the shoots of purple nuts edge since the apical meristem is often shielded from the spray appl ication by outer layers of older leaves. The control of purple nutsedge in th e cultivated check (77.5 % control) was significantly greater than paraquat by itself (47.5 % control). Cultivation is known to induce different nutsedge control responses. When tillage is implemented during the warm weather when it is dry, purple nutsedge plants do not re-establish themselves af ter the mechanical disturbance. Under these conditions, nutsedge tubers are exposed to the so il surface, which causes them to desiccate or freeze and die (Glaze, 1987). However, when cu ltivation is done under warm, moist conditions the plants are able to reestablish themselves after the soil disturbance. Often times, cultivation increases the number of nutsedge plants because it breaks apart the extensive system of underground tubers and rhizomes and thus releas es the tubers from dormancy caused by apical dominance. In other words, cultivation may kill or propagate nutsedge depending on the environmental conditions. All the herbicides and cultivation applications resulted in a higher level of purple nutsedge control (> 47.5% control) compared to the untreated check.

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156 Two months after the initial fa llow applications (when the second fallow applications were made) there were no significant differences betw een the treatments. Purple nutsedge control declined in the herbicide and cultivation tr eatments, because the nutsedge population had begun to rebound during the period of inactivity. After th e second fallow applications of the first year were applied there were signifi cant differences in nutsedge control between treatments. The application of paraquat plus trifloxysulfuron or s-metol achlor (90 and 82.5 % control respectively), and glyphosate alone (85 % contro l) resulted in the highest level of purple nutsedge control. The level of control provide d by paraquat tank mixed w ith trifloxysulfuron (90 % control) was significantly higher than glyphosate plus metolachlor (72.5 % control), glyphosate plus trifloxysulfuron (72.5 % contro l) and paraquat by itsel f (75 % control). However, the level of nutsedge control provided by the all herbicides and their combinations was excellent (> 72.5 % control). The control provided by all the herbicides increased dramatically after the second application (> 72.5 % control) compared to the original application (> 47.5 % control), especially for glyphosat e (increased from 57.5% to 85% control) and paraquat applied alone (control increased from 47.5% to 75%). Nuts edge control was signif icantly better in all the herbicide treatments (> 72.5 % control) compared to the unt reated check and the cultivation check. Purple nutsedge control in the cultivat ed check was nullified due to inactivity. Although cultivation provided initial purpl e nutsedge control, th e population quickly rec overed to original levels. Cultivation needs to take place regul arly to keep purple nutsedge from becoming reestablished. Once cultivation has ceased, then purple nutsedge is able to multiply without restrictions. However, certain he rbicides, such as trifloxysulfur on can provide residual control of purple nutsedge.

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157 Five months after the applica tion of the second fallow treatment s (just prior to planting the spring crop), there were still significant differences between treatments. Trifloxysulfuron tankmixed with either glyphosate or paraquat (87.5 and 77.5 % control respectively), s-metolachlor plus glyphosate or paraquat (82.5 and 70 % c ontrol respectively), gl yphosate alone (70 % control), and cultivation (71.25 % co ntrol) resulted in the highest purple nutsedge control just before planting a spring crop of corn. Trifloxysul furon plus either glyphosate or paraquat (87.5 and 77.5 % control) and glyphosate plus metolach lor (82.5 % control) pr ovided significantly better control of purple nutsedge than paraquat by itself (55 % cont rol). All the herbicides and cultivation methods resulted in sign ificantly higher nutsedge control (> 55 % control) when compared to the untreated check. As discusse d earlier, chemical control of purple nutsedge control requires the use of systemic herbicides such as trifloxysulfuron and glyphosate. The efficacy of post emergent herbicides on purple nuts edge may be increased with the addition of a pre-emergent herbicide, such as s-metolachlo r. In addition, cultivation provides temporary control of purple nutsedge under dry conditions. Paraquat provides burndown control of purple nutsedge, but shoot re-growth from the tubers and meristem ensue. Effect of different fallow treatments on purple nutsedge control yea r 2 Throughout all of the second year all of the herbicides consistent ly controlled purple nutsedge better than the untreat ed and cultivated check (Figur e 2-3). The only sampling date when the cultivated check provided better contro l of purple nutsedge than the untreated check was at the beginning of the season before the tr eatments were applied, indicating that cultivation from the previous fallow extende d control into the second year. There were significant differences in purple nutsedge control between treatments during the second year of fallowing in Citra. After the first herbicide app lication during the second year, all the herbicide treatments, except for glyphosate and paraquat alone controlled purple

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158 nutsedge better than the untreated and cultivated checks. All the herbicides provided similar nutsedge control. After tilling the field for the first time during the second fallo w season, all the herbicides, except for glyphosate alone controlled purple nutse dge better than the untreated and cultivated checks. Trifloxysulfuron treatments controlled purple nutsedge better than glyphosate alone and glyphosate tank mixed with s-metolachlor. Pa raquat alone and paraqua t with s-metolachlor controlled purple nutsedge better than glyphosate alone. Following the second fallow herbicide applicati on during the second year all the herbicide treatments except glyphosate alone controlled purple nutsedge be tter than the untreated and cultivated checks. In addition, treatments cont aining trifloxysulfuron controlled purple nutsedge better than glyphosate alone. All the herbicide treatments, except glyphosat e alone controlled purple nutsedge better than the cultivated check and the untreated check. This may be due to the environmental conditions during the first herbic ide applications. During the fi rst herbicide applications the plants were drought stressed, which may have decr eased the efficacy of glyphosate. In addition, since glyphosate is systemic it takes a longer time to completely c ontrol weeds. Although glyphosate did not completely kill purple nutsedge after the second herbic ide application, those purple nutsedge plants may eventually die be fore planting a crop. Adding s-metolachlor to glyphosate seems to improve purpl e nutsedge control, although not significantly. Paraquat does not typically control purple nutse dge effectively. However, spraying nutsedge with paraquat and cultivating during the summer fallow depleted the carbohydrate reserves in the tubers. In addition, the herbicides were applied when the plants were small and paraquat was able to penetrate the foliage and kill the shoot merist em. The efficacy of paraquat on purple nutsedge,

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159 most likely depends on the size of the target weed s. The cultivated check and the untreated check did not differ in their control of purple nutsedge. During the sec ond year the entire field was cultivated across all treatments, therefore we did not expect to observe difference in nutsedge control between the cultivated and untreated check. However, cultivation from the previous year increased purple nutsedge control during the second year, although not significantly. Trifloxysulfuron offered consistently high cont rol of purple nutsedge. Purple nutsedge was controlled by trifloxysulfuron afte r applications and afte r tilling between herb icide applications. A long term approach is needed to control purple nutsedge with all of the fallow treatments tested in this experiment. Purple nutsedge counts year 2 Overall, if purple nutsedge is left untreated during the fallow season the counts will continue to increase in a linea r fashion (Figure 2-5). In addi tion, cultivating alone increases nutsedge counts throughout the fallow season, but not to the extent of leaving the land idle. There were no dif ferences in purple nutsedge counts between treatments until the last sampling date during the second fallow season. Th e untreated check plots contained more purple nutsedge than all the herbicide treated plots (Fig ure 2-6). Cultivated plots contained similar amounts of purple nutsedge compar ed to the untreated check and the herbicides treated plots. Yellow fallow control ratings year 2 There was a clear separation in yellow nutsedge ratings between the check plots, the paraquat plot and the other herb icide plots during the second year (Figure 2-7). Yellow nutsedge is a bigger plant and has a m ore upright growth habit compared to purple nutsedge. This may prevent paraquat from contacting the shoot apical meristem directly, as it would in prostrate, which would explain why paraquat provide d better control of purple nutsedge.

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160 There were significant differences in yellow nutsedge control between fallow treatments during the second fallow season. Af ter the initial herbicide trea tments were applied all the herbicide treatments except for paraquat prov ided better yellow nutse dge control than the untreated and cultivated checks (Figure 2-8). All the herbicides controlled yellow nutsedge better than paraquat alone. This same pattern was observed after tillage was implemented as well. However, after the second set of herbicide treatments were applied all the herbicides controlled yellow nutsedge better the untreated and cultivated checks. Treatments containing trifloxysulfuron controlled yellow nutsedge bett er than glyphosate plus s-metolachlor. Yellow nutsedge counts year 2 Yellow nutsedge counts declined dram atica lly throughout the fallo wing period regardless of which treatment was implemented (Figure 2-9) The herbicides and tillage reduced yellow nutsedge during the fallow peri od. Significant differences in yellow nutsedge counts between treatments were not seen until after the second fa llow treatments were applied. All the treatment methods (< 3.5 yellow nutsedge/m2) except cultivati on alone (5.5 yellow nutsedge/m2) lowered yellow nutsedge counts significantly compared to the untreated control (11 nutsedge/m2) (Figure 2-10). However, cultivation alone resulted in equa l levels of yellow nutsedge control as all of the other treatments. Implementing any of thes e herbicides during the fallow period would be better than leaving yellow nutsedge grow unchecked. Fallow Period Grasses Crabgrass fallow ratings year 1 After the first year of fallowing all the m et hods that were implemented to control weeds resulted in a significantly highe r level of crabgrass control compared to the untreated check (Figure 2-11). All the herbicides that were a pplied resulted in the hi ghest level of crabgrass

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161 control (> 60 % control). Crabgrass control was signi ficantly higher in all the plots that were treated with glyphosate or gl yphosate tank-mixes and paraquat plus s-metolachlor (> 81 % control) compared to th e cultivated (32.5 % control) or un treated checks. Glyphosate typically provides excellent post-emergent crabgrass control, because it is absorbed systemically and kills the entire plant. S-metolachlor provides excell ent pre-emergent control of crabgrass. Paraquat, on the other hand, does not typically provide excellent control of grass, especially when they are bigger because it is not absorbed wi thin the plant and is not able to directly contact the meristem. In grasses, intercalary meristems are located at the base of nodes and leaf blades, which are hard to reach and allow them to re-grow after the top of the plant has been destroyed. This is why grasses are able to re-grow after they have been grazed by herbivores or cut with lawnmowers. Cultivation alone (32.5 % control) controlled crabgrass better than the untreated check. Cultivation is good at controlling crabgrass. However, crabgrass is able to reestablish from rooted stem nodes after cultivation. This is be cause crabgrass develops a prostrate, crawling growth habit as it becomes mature. Crabgrass fallow ratings year 2 Crabgrass control increased in crem entally throughout the second year of fallowing when herbicides were applied (Figure 212). In other words, crabgra ss control increased further after the second application of herbicides were made compared to the fi rst. In the beginning of the second year of fallowing there we re no significant differences in crabgrass control between treatments. Therefore, the effect of the first year of fallowing did not carry over to the second year. Crabgrass is an annual weed that is primarily propagated through sexual reproduction and is unlikely to have long term population reductions from one fa llow season. In weeds that reproduce sexually there are plenty of seeds in the soil which can germinate when environmental conditions are optimal. A long term approach w ould be needed to cont rol the deposit of seeds

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162 into the soil, and to allow the viable seeds alread y in the soil to become depleted. On the other hand, weeds such as nutsedge that reproduce ase xually through vegetativ e propagation are more likely to be controlled permanently or more di rectly through summer fallow treatments. Lastly, the plants were big when herbicid es were applied therefore, they were not controlled as well as they would have been if they were small, tender, and more susceptible to herbicides. After the first fallow weed control methods we re applied during the second year, there was a significant difference in cra bgrass control between treatment plots. All the herbicide treatments (> 48 % control) were significantly better at controlling crabgrass than the cultivated check (0 % control) or the untreat ed check (Figure 2-13). When th e herbicides were applied they had a direct impact on controlling crabgrass. Re member, all the plots were cultivated during the second year of fallowing, includi ng the untreated check. The reason all treatments were included in case there was carryover from the first fallow season, since the same treatment plots were in the exact same area. This was not th e situation with crabgrass control. One month after implementing the first fallow applications (just prior to applying the second fallow applications), there were still significant differences in crabgrass control between treatments. The treatments that provided th e best crabgrass contro l were glyphosate plus smetolachlor (47.5 % control) and all th e paraquat or paraquat tank-mixes (> 42.5 % control). Glyphosate tank-mixed with s-metolachlor (47.5 % control), paraquat plus s-metolachlor (68.8 % control), and paraquat alone (87.5 % control) gave significantly bett er control than the untreated control, glyphosate by itself (0 % control), glypho sate plus trifloxysulfuron (0 % control), and the cultivated control (0 % contro l). As described earli er, the first application of herbicides was applied to drought stressed plants, which negativ ely affected the efficacy of glyphosate in most weeds. However, the addition of s-metolachlor served to control germinating crabgrass seeds

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163 during the period after the appli cation. Trifloxysulfuron failed to control crabgrass during the second year. Trifloxysulfuron is labeled to s uppress certain grasses, but does not provide control. Paraquat and paraquat tank mixes provi ded good control of crabgrass after the first fallow application of the second year. After the second fallow treatments of the second year were applied there were significant differences in crabgrass control between treatments. All of the herbicide treatments provided the same level of control (> 87.5 % control), which was significan tly higher than the untreated and the cultivated checks (0 % control). The s econd herbicide applicati ons provided excellent crabgrass control. Environmental conditions were ideal to realize the maximum weed control potential. In addition, the weeds were small beca use they were all tilled; therefore they were more easily controlled with herbicides. Crabgrass counts year 2 Crabgrass counts were low after the initial herbicide application, counts increased after cultivation and then cou nts decreased again afte r herbicides were applied (Figure 2-14). This pattern is indicative of what one would expect. Crabgrass is fairly easy to control with herbicides, but once cultivation is performed a flus h of germinating seedlings are stimulated to emerge. There were significant differences in crabgrass counts after th e first fallow treatment of the second year. The treatment that provided the best crabgrass suppression was paraquat tank mixed with s-metolachlor (4 crabgrass/m2), wh ich was significantly similar to the untreated check (14 crabgrass/m2), glyphosate plus s-me tolachlor (7 crabgrass/m2), glyphosate plus trifloxysulfuron (17 crabgrass/m2), paraquat pl us trifloxysulfuron ( 8.5 crabgrass/m2), and paraquat alone (8 crabgrass/m2) (Figure 2-15). Cultivation plots had the highest crabgrass counts (25.5 crabgrass/m2), which were signif icantly similar to the untreated check (14

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164 crabgrass/m2), glyphosate alone (20.5 crabgrass /m2), and glyphosate plus trifloxysulfuron (17 crabgras/m2). All the paraquat treatments (< 8.5 crabgrass/m2) and glyphosate plus smetolachlor (7 crabgrass/m2) resulted in significa ntly lower crabgrass count s than the cultivation alone (25.5 crabgrass/m2). Alt hough cultivation was not performed yet during the second year, prior cultivation events led to an increase in crabgrass numbers by eliminating competition with other plants. Paraquat was very effective at cont rolling crabgrass. Glyphosate did not perform as well as expected during the first fallow applicatio n, which is attributed to drought stressed plants. However, the addition of s-metolachlor did im prove the efficacy of glyphosate on crabgrass. Goosegrass control ratings year 1 Goosegrass control increased when herbicides and cultivation were implemented and then control decreased slowly after they were impl emented (Figure 2-16). Following the first fallow application of the first year there were significan t differences in gooseg rass control between treatments. Goosegrass was controlle d best in all paraquat treatment (> 87.5 % control) and glyphosate tank mix (> 85 % control) treatment plots (Figur e 2-17). S-metolachlor plus either glyphosate or paraquat (97.5 % control) provided significantly better goo segrass control than glyphosate alone (77.5 % control). All fallow weed control met hods, including herbicides and cultivation (> 30 % control) controlled goosegrass be tter than the untreated check. All herbicides (> 77.5 % control) provided better weed control than the cultivated check (30 % control). All the herbicides provided good post-emergent control of goosegrass. However, the addition of s-metolachlor to either glyphosate or paraquat dramatically increased the preemergent control of goosegrass, and therefore increased the overall control of goosegrass. Two months after the first fallow treatments we re applied (prior to applying the second set of fallow treatments) there were still signifi cant differences in goos egrass control between

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165 treatment plots. The level of goosegrass control was significantly higher in all the treatments (> 35 % control) when compared to the untreated check. The best goosegrass control was obtained from using glyphosate alone (57.5 % control), gly phosate tank mixed with s-metolachlor (67.5 % control), all the paraquat/para quat tank-mix combinations (> 40 % control), and the cultivated check (42.5 % control). Glyphosat e plus s-metolachlor (67.5 % c ontrol) controlled goosegrass significantly better than glyphos ate tank mixed with trifloxy sulfuron (35 % control). Smetolachlor provided pre-emergent goosegrass cont rol when added to glyphosate or paraquat but trifloxysulfuron did not. In crabgras s, the same results were observed. After the application of the second fallow tr eatments during the first year there was a significant difference in goosegrass control between treatments. A ll herbicides (100 % control) significantly controlled goosegrass be tter than the untreated and cultiv ated checks (0 % control). The weeds were smaller and more susceptible to herbicides during the second application, because the first application killed and burne d down the existing weeds. Therefore the herbicides provided more effective control because the targeted weeds were small and more susceptible to control. Goosegrass control ratings year 2 Goosegrass was not present in the ex perimental area the second year until toward the end of the fallowing period. There were significant differences in goosegrass control between treatments during the second year of fallowing. The same pattern was observed in goosegrass control on the last sample date of the second year as the last date during the first year. All the herbicide treatments (100 % control) provided better goosegrass control th an the untreated and cultivated checks (0 % control) (Figure 2-18). Consistent control of goosegrass was achieved using two consecutive fallow herbicide appli cations for both years of the study. The same factors contributed to the increased effi cacy of the second herbicide application.

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166 Goosegrass counts year 2 Goosegrass counts were signifi cantly different between treat m ent plots during the second year. The untreated (27 goosegrass/m2) and cu ltivated checks (26 goosegrass/m2) had higher goosegrass counts than the plots treated with herbicides (< 0.5 goosegrass/m2), following the last herbicide application of the second year (Figure 2-19). Ex cellent goosegrass control was obtained by either glyphosate or pa raquat without the presence of other herbicides. These results were fairly consistent with the trends found for other grass species. Corn fallow ratings year 2 Control of volunteer corn increased throughout the fallow period during the second year in all of the fallow treatment plots, except in th e untreated and cultivated check plots, following the spring corn crop (Figure 2-20). Initially there were no significant differences in the control of corn (as a weed) during the off-season at the begi nning of year two (Figure 2-21). After the first fallow treatments were applied, there was significantly higher corn control in all of the plots that were treated with herbicides (> 63 % control) compared to th e untreated and the cultivated control (0 % control). Controlling volunteer cr ops during the fallow season is another important reason for implementing weed control methods. Harmful pests, diseases, and viruses can be harbored in volunteer crops dur ing the fallow period. Controlling these crops during the fallow season has the potential to break the disease cycl e and lower the intensity of infestation in the subsequent crop. All herbicides tested could be used to adequately control unwanted corn plants between growing seasons. Crowfootgrass control ratings year 2 Significant differences in crowfootgrass co ntrol were observed between the different fallow weed control m ethods prior to bed prepar ation for planting cabbage. All the herbicides (100 % control) used controlled crowfoot gr ass significantly better th an the untreated and

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167 cultivated checks (0 % control) (Figure 2-22). The second herb icide application was made to small plants; therefore the level of control provi ded by the herbicides was excellent. Other grass species responded similarly to the fallow treatments. Fallow Broadleaves Amaranth fallow control ratings year 1 Am aranth control was very high following herb icide applications and cultivation events during the first year of fallowing (Figure 2-23). The high level of amaranth control was maintained in the trifloxysulfuron treated pl ots, even between treatment applications. Trifloxysulfuron has shown residual cont rol in many other weed species. Following the first fallow weed control applicat ions there were significant differences in amaranth control between treatments. All of the treatment methods gave significantly better amaranth control (> 90 % control) than the untreated check (Figure 2-24). The plots that were treated with paraquat (by itself or tank-mixed) (> 97.5 % control) or glyphosate tank-mixes (100 % control) had the greatest amount of amaranth control. When glyphosate or paraquat was tank-mixed with either s-metolachlor or trifloxysulfuron (100 % control) it provided amaranth control significantly higher than that provide d by glyphosate alone (90 % control) or cultivation (90 % control). The addition, of s-metolachlo r and trifloxysulfuron has improved the weed control activity of many other weeds, as well. Adding thes e herbicides provided a complete range of control including post-em ergent control of existing plants and pre-emergent control of germinating seedlings. A month after the first fallow treatments were applied significant differences in amaranth control were still observed. Th e highest levels of amaranth control was provided by glyphosate alone (57.5 % control), glyphosate plus trifloxysulfuron (82.5 % control), and paraquat plus trifloxysulfuron (77.5 % control). Glyphosate plus trifloxysulfur on (82.5 % control) controlled

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168 amaranth significantly better than glyphosate tank -mixed with s-metolachlor (40 % control), paraquat plus s-metolachlor (37.5 % control), paraquat alone (17.5 % control), cultivation (45 % control), and the untreated check. Similar results were observed for paraquat plus trifloxysulfuron (77.5 % control), ex cept this combination did not significantly control amaranth better than the cultivated check (45 % control). All treatments methods (> 37.5 % control), except paraquat alone (17.5 % control), outperfor med the level of amaranth control in the untreated check. The addition of trifloxysulfuro n certainly improved the duration of amaranth control. In addition, glyphosate controlled amar anth in a persistent manner (complete kill), whereas paraquat on provided temporary control of amaranth (burndown). After the second fallow herbicide treatments we re made there were significant differences in amaranth control between treatments. The herbicide treatment methods (100 % control) all gave better amaranth control than the untreated and cultivated checks (0 % control). All the herbicides are capable of completely controlling amaranth. The timing of application and more specifically the weed growth st age are important factors influencing herbicide efficacy. Five months after implementing the second fa llow herbicide treatmen ts and cultivating (prior to planting the spring cr op) all the fallow techniques (> 75 % control) provided significantly higher amaranth c ontrol than the untreated check. There were no differences between the other treatments, in respect to amaranth control. Cultivation without herbicides gave good amaranth control when it is im plemented, but the e ffects are temporary. Amaranth fallow control ratings year 2 During the second year am aranth control was high in the herbicide treated plots after herbicides were applied, and consistently low in the untreated and cultiv ated checks (Figure 225). Similar to the first year of fallowing, trif loxysulfuron treated plots had consistently high

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169 amaranth control throughout the entire fallow period; meanwhile the control provided by other herbicides was only temporary. After the first set of fallow herbicide appli cations were made during the second year there were significant differences in amaranth control be tween treatments. The pl ots that were treated with herbicides (> 75 % control) resulted in higher amaranth control than the untreated and cultivated checks (0 % control) (F igure 2-26). All the herbicides (> 75 % control) provided similar levels of amaranth control. After tillage was performed following the first set of fallow herbicide applications there were significant differences in amaranth control between treatments. Trifloxysulfuron tankmixed with either glyphosate or paraquat (100 % c ontrol) controlled amaranth better than the other treatments (< 25 % control). This finding was c onsistent with the results found for amaranth control during the first year of fallowing. In addition, th e same trend was observed in many other weeds for both fallowing seasons. Following the second fallow application of the second year there were significant differences between treatments. Amaranth contro l was greatest in the areas where herbicides were applied (100 % control) compared to the un treated and cultivated checks (0 % control). Optimum amaranth control was realized when app lications were made under ideal environmental conditions to small, succulent, susceptible amaranth seedlings. Amaranth counts year 2 Am aranth counts were relatively low in all th e plots regardless of tr eatment after the first fallow treatments were applied (Figure 2-27). Then amaranth counts increased following cultivation. Even after cultivation, amaranth num bers were suppressed in the trifloxysulfuron treated plots. After the second set of fallow he rbicide applications amaranth counts decreased again, except in the cultivated and untreated check s. Although cultivation kills the majority of

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170 emerged amaranth plants, it does not prevent viab le seeds from emerging in the soil. In many cases the opposite reaction is occu rs, cultivation often results in a surge of emerging seedlings, especially rudimentary species such as amaranth. However, trifloxysulfuron provided residual control to hinder amaranth emergen ce even after tillage events. There were no significant di fferences in amaranth counts between treatments until after the second treatments were made during the second year. The cultivated (115 amaranth/m2) and untreated checks (64.5 amaranth/m2) contained the highest numbers of amaranth (Figure 2-28). The cultivated check (115 amaranth/m2) had higher numbers of nutsedge compared to the plots treated with herbicides (< 3 amaranth/m2). In addition, there was no difference between the amount of amaranth in the untreated check plot (64.5 amaranth/m2) compared to the herbicide treatments (< 3 amaranth/m2) or the cultivated check (115 amaranth/m2). All the herbicides gave excellent suppression of emerged amaran th seedlings. Cultivation controlled emerged amaranth, but resulted in a flush of germinating seeds. Purslane fallow ratings year 1 Purslane control was very high when the first fallow applications were m ade, control declined drastically afterward in all plots, except for those treate d with trifloxysulfuron, and then control increased dramatically af ter the second herbicide applicatio ns were applied (Figure 2-29). In addition, purslane control dissipated in th e cultivation plots th roughout the fallow season. After the first fallow weed control methods were applied there were significant differences in purslane control between the various treatment plots. All the treatments containing paraquat (> 97.5 % control) and both the gly phosate tank mixes (with s-meto lachlor or trifloxysulfuron) (100 % control) resulted in the highest control of common purslane after th e first treatment were applied (Figure 2-30). All the fallow methods resulted in si gnificantly better weed control (> 92.5 % control) when compared to the untreated check. In addition, glyphosate tank mixed with

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171 either s-metolachlor or trifloxysulfuron and paraquat combined with s-metolachlor provided significantly higher purslan e control (100 % control) than th e cultivated check and glyphosate alone (92.5 % control). In summ ary, glyphosate and paraquat provi de good control of purslane, but tank-mixing these herbicides with either smetolachlor or trifloxys ulfuron can increase the level of control provided. One month after the first fallow treatments were applied the first year, there were significant differences in purslan e control between trea tments. Trifloxysulfuron plus either glyphosate (87.5 % control) or paraquat (75 % cont rol) controlled purslane the best one month after the first fallow treatments were applied. All the treatments except glyphosate by itself (20 % control) provided significantly better contro l than the untreated check. Glyphosate plus trifloxysulfuron (87.5 % control) gave a significantly greater am ount of control than glyphosate alone (20 % control), glyphos ate plus s-metolachlor (47.5 % control), paraquat plus smetolachlor (47.5 % control), paraquat alone ( 47.5 % control) and cu ltivation alone (50 % control). Paraquat with trifloxysulfuron (75 % control) gave signi ficantly higher purslane control than glyphosate alone (20 % control). Trifloxysulfuron provided good residual contro l of purslane in the period following the first herbicide application. Following the second fallow treatments of the fi rst year all the herb icides used in the treatments provided significantly higher control (100 % control) than the untreated check and the cultivation check (0 % control). The second herbic ide applications were a pplied to small plants under ideal environmental conditions which allo wed the herbicides to provide the maximum level of control.

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172 Purslane fallow ratings year 2 Purslane control increased th roughout the second year of fallowing (Figure 2-31). In addition, a high level of purslane control was esta blished and m aintained in the trifloxysulfuron treated plots. At the start of year two, there were not any significant differences in purslane control between treatments. This indicates that there was not re sidual control of purslane from the first year of fallowing. The lack of residual control between years of fallowing is consistent with many other annual, sexually reproducing weeds. In the period after the first set of herbicid e treatments were applied and cultivation was performed during the second year of fallowing there were significant differences in the level of purslane control between treatm ents. Trifloxysulfuron plus either glyphosate or paraquat provided significantly higher purslane control (1 00 % control) than all the other fallow treatments (< 20 % control) (Figure 2-32). These findi ngs are consistent w ith the results found during the first year of the study. Following the second set of fallow herbicide tr eatments were applied during the second year there were significant differences between treatments. Purslane was controlled at a significantly higher level where herbicides were applied (100 % control) compared to the untreated control and the cultivated check (0 % control). The result s found during the second year of fallowing were consistent with the observations made during the first fallow season and are attributed to the same factors. Purslane counts year 2 Throughout the second year of fallowing pursl ane counts declined regardless of fallow trea tment, except for cultivation (Figure 2-33). All the plots including the untreated check were tilled during the second year. It is believed that purslane counts were hi gher in the cultivated

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173 check than in the untreated check because ther e was less nutsedge competition with purslane in the cultivated check compared to the untreated check. There were no significant diffe rences in purslane counts betw een treatments after the first fallow applications (both herbicides and tillage ) of the second year. After the second fallow herbicide treatments were applied there were sign ificant differences in pu rslane counts between plots. The cultivated check (108 purslane/m2 ) contained a significantly higher number of purslane compared to all the other plots (< 29 purslane/m2) (Figure 2-34 ). Purslane count results are in tandem with purslane control results. Cu ltivation increased the am ount of purslane present because it reduced the amount of competition with other weeds such as nutsedge and increased the amount of germinating seeds from the soil seed bank. Florida pusley control ratings year 1 At the end of the first year of fallowing there were significant differe nces in pusley control between treatm ents. All of the fallowing methods (> 77.5 % control) controlled pusley significantly greater than the untreated check (Figure 2-35) These fallow methods provided similar levels of pusley control. These results ar e consistent with the re action of other broadleaf weeds to the treatments during year 1. Florida pusley control ratings year 2 Florida pusley control increased during the f allow season for all the herbicide treatments (Figure 2-36). After the first fallow treatments (herbicide application followed by cultivation) were applied the second year, there was significant differenc es in pusley control between treatments. Trifloxysulfuron either ta nk-mixed with glyphosate or paraquat (> 95 % control) provided the greatest level of pus ley control (Figure 2-37). Para quat plus trifloxysulfuron (100 % control) controlled Florida pusley significantly better than glyphosate alone (22.5 % control), glyphosate tank-mixed with s-metolachlor (50 % control), paraquat plus s-metolachlor (22.5 %

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174 control), paraquat alone (0 % control), the un treated check and the cultivated check (0 % control). Glyphosate plus trifloxysulfuron (95 % control) provided the same relative level of control as paraquat tank mixed with trifloxysulfuron (100% control), except that it did not control pusley significantly better than glyphos ate plus s-metolachlor (50 % control). Trifloxysulfuron gave excellent residual control of pusley after the plots were cultivated. The other herbicides did not provide control of pusley after the soil was disturbed by cultivation. The untreated control, paraquat by itself (0 % control) and the cultivated check (0 % control) did not control Florida pusley and this level of control was significantly lower than all the treatments except for glyphosate alone (22.5 % control) and pa raquat plus s-metolach lor (22.5 % control). Paraquat, glyphosate, and s-metolachlor did not provi de residual control of Florida pusley to any considerable degree. After the last fallow treatment during the second year there were signif icant differences in pusley control between treatments. All the he rbicides (100 % control) controlled pusley significantly better than th e untreated and cultivated checks (0 % control). Small, tender pusley plants were completely controlled by all the herbicides used in the experiment. Cultivating before applying herbicides increased the efficacy of the herbicides compared to the first herbicide application, which was made to larger weeds. Florida pusley counts year 2 The untreated control had the highest Florida pusley counts. P usley numbers increased in the untreated and cultivated check plots throughout the fallow seas on (Figure 2-38). In contrast, the number of pusley plants decreas ed during the fallow period in the plots that were treated with the herbicides used in this trial. There were not significant differences in Florida pusley counts between treatments at either sampling date. The differences in pusley counts were probably not significant due to the high va riability between plots.

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175 Cutleaf evening primrose control ratings year1 Glyphosate alone (95 % control) and glyphos ate or paraquat tank-m ixes containing trifloxysulfuron or s-metolachlor (> 95 % control) controlled cutle af evening primrose the most and the level of control was significantly higher than cultivation alone (82.5 % control) (Figure 2-39). Glyphosate tank mixed with s-metolachlor (96.3 % control) or trifloxysulfuron (97.5 % control) provided greater cutleaf evening primrose control than paraquat alone (87.5 % control). All the treatments (> 82.5 % control) controlled cutleaf evening primrose significantly better than the untreated control. Glyphosate provides excellent cont rol of cutleaf eveningprimrose, however adding trifloxysu lfuron or s-metolachlor to the spray solution increases cutleaf evening primrose control, especia lly when using paraquat. Cutleaf ground cherry control ratings year 2 Trifloxysulf uron with either gl yphosate or paraquat provided c onsistent control of cutleaf ground cherry during the second year of fallowing (Figure 2-40). The other herbicides provided high levels of control when they were applied, but did not provide much residual control. This pattern of response from the fallow treatments is similar to other annual, broadleaf, sexually propagated weeds. At the start of year two all th e treatments plots where herbicid es were applied the previous year, there was a significantly higher level of control (> 65 % control) compar ed to the untreated and the cultivated checks (7.5 % control) (Figure 2-41). These results i ndicate that there was carryover control from the previous year of fallowing. The use of herbicides and to some degree cultivation, prevented cutleaf ground cherry plants from flowering, setting seeds, and depositing seeds into the soil seed bank. Glyphosate alone (87.5 % control) did not control cutleaf gr ound cherry as well as the other herbicide and herbicide combinations (> 95 % control) after the first fallow herbicide

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176 application. The soil was dry and plants were sl ightly wilted during the first fallow herbicide application of the second year. It is hypothesize d that the dry conditions did not allow glyphosate to be absorbed and translocated to its maximum potential. Be cause of the condition described the efficacy of glyphosate was compromised. Ho wever, the addition of s-metolachlor or trifloxysulfuron had a synergistic effect that improved the effectiveness of glyphosate. All the herbicide treatments provided better control (> 87.5 % control) of cutl eaf ground cherry than the cultivated check (0 % contro l) and the untreated check. After tilling all the plots after the first fallo w herbicide applications, trifloxysulfuron tankmixed with either glyphosate or paraquat (100% cont rol) provided a higher level of control than all the other fallow w eed control methods (< 25 % control). Trifloxys ulfuron provided residual control of cutleaf ground cherry, even after cultivating. This same phenomenon was realized with many other broadleaf, annual weeds, which are primarily dispersed by seeds. After the second herbicide appl ications of the second year all the herbicides (100 % control) used in this experiment for fallow weed control provided better control of cutleaf ground cherry compared to the cultivated check (0 % co ntrol) and the untreated check. Cultivating and then applying herbicides is a very effective pr otocol to control weeds. This procedure is commonly used in stale seedbed preparation. Cultiva ting stimulates a flush of seedlings and herbicides kill these tender, highly susceptible se edlings without disturbing the soil. Therefore two objectives are accomplished, the existing seed lings are killed and new seedlings do not emerge since the soil is not disturbed (s uch as in no-till agri cultural operations). Cutleaf ground cherry counts year 2 The counts of cutleaf ground cherry were lower in all the treatm ent plots when compared to the untreated control, across all treatment dates (Figure 2-42 ). Cutleaf ground cherry counts were significantly higher in the unt reated control after applying th e first fallow applications (12

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177 cutleaf ground cherry/m2) and afte r cultivating the field after th ese applications (52 cutleaf ground cherry/m2 compared to all th e other fallow treatment plots (< 7 cutleaf ground cherry/m2) during the same time period (Figure 2-43). There were no significant differences in cutleaf ground cherry counts in th e plots after the second fallow a pplications were applied. Carpetweed fallow control ratings year 2 Trifloxysulf uron provided consistently high control of carpetweed throughout the second year of fallowing (Figure 2-44). In addition, al l the herbicides provide d excellent carpetweed control after they were applied. Cultivation and th e untreated plots did not control carpetweed. Trifloxysulfuron mixed with either glyphosat e or paraquat (100% c ontrol) controlled carpetweed significantly better than the other treatments (0% contro l) after cultivation following the first fallow herbicide appli cations (Figure 2-45). Trifloxysulfuron provided residual control in many other weeds in the field as well. After the second fallow applications there we re significant differences in carpetweed control between treatments. Carpetweed was contro lled significantly better in plots treated with herbicides (100% control) compared to the un treated and cultivated checks (0% control). Complete control of carpetweed was controlled with all herbicides after the plots were tilled; therefore there is no advantage of using any pa rticular herbicide over another. The least expensive herbicide would be the best choice to control carpetweed and there in no need to tankmix herbicides. Carpetweed counts year 2 Carpetweed counts decreased towards the end of the second year of fallowing regardless of treatm ent (Figure 2-46). There were not signifi cant differences in carpetweed counts until after the second herbicide applications were applied. After the second fallow application, all the herbicide treatment plots had a sign ificantly lower carpetweed density (< 0.5 carpetweed/m2)

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178 than the untreated (9 carpetweed /m2) and cultivated checks (11 carpetweed/m2) (Figure 2-47). The results obtained for the various treatment counts are consistent with the control ratings that were taken. All the herbicides used in the expe riment provide excellent carpetweed control and would be practically implemented in modern horticultural production. Redweed control ratings year 2 There were significan t differences in redweed control between treatmen ts by the end of the season. Redweed was controlled best in all the plots that were treated with herbicides (100 % control) and this level of c ontrol was significantly higher than the untreat ed and cultivated checks (0 % control) (Figure 2-48). The herbic ides were applied to young weeds that emerged after being sprayed and tilled. At this stage of development the weeds were more effectively controlled. Cabbage Vigor Ratings and Weed Control Ratings during the Crop Purple nutsedge, yellow nutsedge, crabgrass, an d purslane control differed significantly in the cabbage crop between fallow treatment plots. In addition, purple nutse dge, crabgrass, cutleaf evening primrose, and purslane control was signif icantly different between pre-plant herbicide subplots during the growing seas on. Lastly, cabbage vigor was significantly different between fallow treatment areas. Purple Nutsedge Fallow treatment effect Glyphosate tank mixed with s-metolachlor (65.8% control) or tr ifloxysulfuron (78.3 % control), paraquat (72.5 % control) and paraquat tank-mixed with s-metolachlor (79 % control) or trifloxysulfuron (65 % control) that were applied during the summ er controlled purple nutsedge the best initially after cabbage was planted (Figure 2-49). Paraquat plus s-metolachlor (79 % control) controlled purple nutsedge in the initial stages of the crop better than glyphosate

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179 alone (60 % control), cu ltivation alone (52.5 % control), and the untreated check. Glyphosate plus trifloxysulfuron (78.25 % control) and paraquat alone (72.5 % control) controlled purple nutsedge better than the cultivated (52.5 % control) and untrea ted checks. All the treatment methods provided significantly better nutsedge control (> 52.5 % control) when compared to the untreated check. On the second sampling date during the growi ng season, there were significant differences in purple nutsedge control betw een fallow treatments as well. The untreated check (18.8 % control) did not control purple nutsedge as well as the othe r methods of weed control (> 71.9 % control); regardless of which pre-plant herbic ide was used. The cult ivated control (94.4 % control) and all the fallow herbicide treatments (> 77.5 % control) except for glyphosate plus smetolachlor (71.9 % control) provided the highe st level of purple nutsedge control. Hoeing every to weeks (cultivated check) (94.4% contro l) during the crop provided significantly better purple nutsedge control than glyphosate plus s-metolachlor (71.9 % control). On the last sampling date of sampling, all the herbicide fallow treatments (> 68 % control) and hand hoeing (85.6 % control) du ring the growing season provided the highest level of purple nutsedge control, this was signi ficantly better than th e untreated control (18.8 % control). In summary, applying herbicides during th e fallow period provided control of purple nutsedge that carried over into the cropping season. All of th e fallow herbicides provided similarly high purple nutsedge control in the crop. Initially hand hoeing (cultivation) did not control purple nutsedge as well as the fallow herbicides. Howeve r, after hand hoeing routinely every other week cultivation provided excellent purple nutsedge control. Multiple consecutive fallow herbicide applications made over two contiguous years of both systemic and burndown post emergent materials tank-mixed with pre-em ergence herbicides did not cause drastically

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180 different nutsedge control duri ng the crop, although there were major differences during the summer when they were applied. Tradition knowledge of both herb icides and nutsedge extensive underground growth would lead one to expect that burndown herbicides would not control purple nutsedge to the same degree as syst emic herbicides. Although this may true for a single herbicide application, multiple herbicide app lications coupled with multiple tillage events compound each other and provide good contro l of purple nutsedge even when burndown materials are used. This is because paraquat destroyed the above ground shoots and even killed the shoot meristem when it was applied to small purple nutsedge plants because greater canopy penetration was achieved. Fallow cultivation broke up nutsedge tuber dormancy by breaking apical dominance thus allowing the tubers to sp rout then the shoots to be destroyed with herbicides. In addition, routin e cultivation alone implemented at short intervals (14 days) during the crop provided excellent purple nutsedge contro l because it disrupted the growth of existing shoots, depleted reserves in the tubers and t hus did not allow purple nu tsedge to re-establish. Pre-plant treatment effect In referen ce to the efficacy of pre-plant herbic ides in conjunction with fallow weed control methods on purple nutsedge, s-meto lachlor (> 80 % control) provi ded significantly better control than oxyfluorfen (> 68 % control) (Figure 250). S-metolachlor is known to suppress purple nutsedge but not provide ad equate control when used by itself. However, if used as pre-plant herbicide in conjunction with fallow herbicides it can provide benefici al effects that contribute to the overall level of purple nutsedge control. Wh en s-metolachlor is used following fallow weed control methods good control of purple nutsedge is achieved. Yellow Nutsedge Control in Cabbage There were significant differences in yellow nutsedge control between treatm ent methods. All the methods used to contro l weeds during the fallow period (> 52.5 % control) controlled

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181 yellow nutsedge better than the untreated check during the crop (Figure 2-51). In addition, all the herbicide treatments (> 80 % control) controlled yellow nutsedge better than the cultivated check (52.5 % control). All the herbicide treatments (> 85 % control) except for glyphosate alone (80 % control) provided th e best yellow nutsedge control. S-metolachlor tank-mixed with either paraquat or glyphosate (> 98 % control) controlled yellow nutsedge significantly better than glyphosate by itself (80 % control). S-metolachlor is extremely effective at controlling yellow nutsedge. Fallow herbicide applications ca n provide excellent cont rol of yellow nutsedge in the subsequent crop. The r eason that glyphosate alone did not perform to the same standards at controlling yellow nutsedge is unclear. It may be possible th at applying glyphosate to small sized yellow nutsedge plants not optimal becau se the weeds do not absorb enough of the herbicide to kill the underground tubers. Crabgrass Control in Cabbage Fallow treatment effect All the fallow treatm ent systems (> 83 % cont rol) controlled crabgras s significantly better than the untreated check (58.8 % control) dur ing the first sampling date during the crop, independent of which pre-plant herbicide was applied (Figure 2-52). Glyphosate alone (90.6 % control), S-metolachlor tank-mixed with glyphosate or paraquat (> 90% control), and cultivation (100 % control) controlled crabgrass the best. Hand-hoeing on a biweekly basis (100% control) controlled crabgrass significantly better than paraquat alone (83.8 % control) and trifloxysulfuron mixed with either glyphosate (86. 3 % control) or paraquat (87.5 % control). There were also differences in crabgrass c ontrol between fallow treatments, on the second sampling date. All treatments (> 70 % control) controlled crabgr ass significantly better than the untreated check (40 % control). Cultivation (98 % control) controlled crabgrass better than

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182 paraquat plus trifloxysulfuron (70.6 % c ontrol). All the other herbicides (> 78.8 % control) were equally as effective as hand hoeing (98 % control) at contro lling crabgrass. Cultivation had an immediate positive effect at controlling crabgrass. Scheduling frequent hand hoeing during the crop will effective control the existing crabgrass population and prevent future infestations from taking grasp. Trifl oxysulfuron did not control crabgrass in the fallow period; therefore it was not expected to control crabgrass during th e cropping season. The addition of trifloxysulfuron to glypho sate or paraquat decreased the control of those herbicides in most cases; however the decrease in control was not significant. It is unc lear if the addition of trifloxysulfuron yields an antagonistic response on crabgrass control when applied with other herbicides. However, the addition of trifloxysul furon is definitely not beneficial to control crabgrass. In contrast, the addition of s-metola chlor in the fallow period did increase crabgrass control but not significantly. Pre-plant treatment effect There were also sign ificant differences in crabgrass control between pre-plant herbicide treatments. On both sampling dates oxyfluorfen (> 90 % control) provided higher control of crabgrass than s-metolachlor (> 65 % control) (Figure 2-53). Oxyf luorfen would be preferred to s-metolachlor to control crabgrass in cabbage. Although, s-metolachlor is more effective at controlling purple nutsedge, it did not control most other weeds (most annual weeds) as well as oxyfluorfen. According to personal communication with Dr. Stall, th is is unusual. S-metolachlor usually provides better control of grasses compared to oxyfluorfen. Cutleaf Evening Primrose Fallow treatment effect There were significan t differences in cutleaf evening primrose control between pre-plant herbicides, but not between fallow treatments. Sin ce cutleaf evening primrose is a winter annual

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183 it was not present and/or prevalen t during the fallow period. Ther efore, it is not practical to target this weed during the summer fallow season, but instead it is more efficient to focus control efforts during the cool se ason (cropping season). Pre-plant treatment effect Oxyfluorfen (96.6 % control) controlled cutleaf evening prim rose significantly better than s-metolachlor (75.5 % control) (Figure 2-54). As seen with other types of weeds oxyfluorfen was more effective at control mo st annual species than s-metolach lor. Since excellent cutleaf evening primrose is achieved with oxyfluorfen as a pre-plant herbicide, there is no need to apply fallow herbicides or cultivate during the fallo w period to control this particular weed. Purslane Control in Cabbage Fallow treatment effect Cultivation (100 % control) and the u ntreated check (82.5 % control) provided the best purslane control in cabbage dur ing the first sampling date (F igure 2-55). Hand hoeing (100 % control) every other week cont rolled purslane significantly better than all the chemical fallow methods (< 70 % control). The untreat ed check (82.5 % control) pr ovided better control of purslane than glyphosate alone (60 % control) and paraquat plus smetolachlor (61.3 % control). The methods that provided the best purslane control on the second sampling dates were the untreated check (87.5 % contro l), glyphosate alone (86.25 % c ontrol), glyphosate tank-mixed with trifloxysulfuron (81.3 % control), and the cultivated check (99.4 % control). Cultivation (99.4 % control) provided significantly higher control of purslane than all the treatments containing paraquat (< 71.3 % control) and glyphosate plus s-metolachlor (74.4 % control). Even the untreated check (87.5 % control) provid ed significantly better purslane control than paraquat plus trifloxysulfuron (68.1 % control). It is unusual for the untreated check to control a weed better than the treated plots. However, it is possible that the competition from other weeds

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184 such as purple nutsedge was too intense for purslan e to become established. In the treated plots competition with purslane from other weeds was much less and thus purslane was allowed to grow freely. Since purslane is an annual weed that is propaga ted by seed, the fallow treatments did not provide control from the fallow period af ter the field was cultivated and prepared for planting. Pre-plant treatment effect Purslane was controlled to a higher degree by the pre-plant herbicide oxyfluorfen (> 98 % contro l) rather than s-metolachlor (< 61 % control) on both sampling dates (Figure 2-56). Oxyfluorfen was excellent at controlling purslane and should be recommended for pre-plant control in cabbage. Fallow weed control met hods are most likely not necessary to control purslane in vegetables, unless there are no effect ive pre-plant herbicides labeled for a specific crop. Cabbage Weed Counts Fallow treatment effect: There were significant differences in purple nutsedge counts in cabbage between the fallow treatment plots. In addition, there were differences in yellow nutsedge and crabgrass counts between pre-plant herbicide treatments. Purple nutsedge counts were significantly highe r in the untreated tr eatments (217 purple nutsedge/m2) compared to all the other fallow tr eatments (< 49 purple nutsedge/m2) (Figure 257). The counts in the other fallow treatments were similar during the cropping season (15 49 purple nutsedge/m2). These findings are similar to the purple nutsedge rating results, but not exactly the same. As noted earlie r, control ratings may differ s lightly than counts. All living nutsedge in any condition was tallied in the counts. However, the ratings took into account the condition the plants were in when they were observed.

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185 Yellow nutsedge counts were significantly higher in the oxyfluorfen (0.9 yellow nutsedge/m2) treated plots compared to plots tr eated with s-metolachlo r (0 yellow nutsedge/m2) (Figure 2-58). These results are consistent w ith the results found with the purple nutsedge ratings. S-metolachlor provided better cont rol of both purple and yellow nutsedges than oxyfluorfen. Crabgrass numbers were significantly higher in the plots treated with s-metolachlor (4.6 crabgrass/m2) than oxyfluorfen (0.9 crabgrass/m2 ) (Figure 2-59). Oxyfluorfen controlled most annual weeds better than s-metolachlor, but not perennial nutsedge. The results for crabgrass counts response to these pre-plan t herbicides are consistent with the findings from the crabgrass control ratings. Applying oxyfluorfen before planting cabbage is highly recommended to control crabgrass even if the field was treated during th e fallow period. Cabbage Vigor Fallow treatment effect : Cabbage vigor differed significan tly between fallow treatments but not between pre-plant herbicides. The cabbage in the untreated plots (76 % vigor) were the least vigorous, but this was not significantly lower than the cabba ge vigor in the glyphosate plus trifloxysulfuron (83 % vigor) and cultivation plot s (79 % vigor) (Figure 2-60). The herbicide treatments provided the most vigorous cabbage (> 85.9 % vigor) except for glyphosate tankmixed with trifloxysulfuron (83 % vigor). The cabbage in the paraquat plus s-metolachlor (88.8 % vigor) plots were significantly more vigorous than the cabbage in the glyphosate plus trifloxysulfuron (83 % vigor) and cultivation plot s (79 % vigor). In summary, vigor was less in the untreated plots, cultivated pl ots, and trifloxysulfuron treated pl ots. Cabbage vigor was less in the untreated plots because ther e was an overwhelming amount of weeds present that negatively impacted cabbage growth. The vigor was proba bly less in the cultivat ed plots because the

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186 cabbage roots were disturbed sli ghtly by frequent hoeing. It s eems trifloxysulfuron may have a negative impact on cabbage growth and developmen t even when it is applied during the summer. Cabbage Yield Year 2 Cabbage number, total weight and average weight differed signifi cantly b etween fallow treatment plots. The total yield and the average weight per head of cabbage were significantly different between pre-plant herbicide treatments. Cabbage Number Fallow treatment effect: The treatment plots with the hi ghest number of cabbage were glyphosate by itself (12.6 cabbage/15 LBF), glyphosate tank-mixed with trifloxysulfuron (12.1 cabbage/15 LBF), and all of the paraquat treatments (> 12.9 cabbage/15 LBF) (Figure 2-61). The untreated check (10.25 cabbage/15 LBF), glyphosate plus s-metolachlor (10.6 cabbage/15 LBF), glyphosate tank-mixed with trifloxysulfur on (12.1 cabbage/15 LBF), and cultivation (10.9 cabbage/15 LBF) resulted in the lowest cabbage counts per plot. Paraquat plus trifloxysulfuron (13.1 cabbage/15 LBF) resulted in a higher numbe r of surviving cabbage at harvest than the untreated check (10.25 cabbage/15 LBF), glyphosat e plus s-metolachlor (10.6 cabbage/15 LBF), and biweekly cultivation (10.9 cabbage/15 LBF). All the treatments containing paraquat (> 12.9 cabbage/15 LBF) had higher cabbage numbers th an the untreated check (10.25 cabbage/15 LBF) and glyphosate plus s-metolachlor (10.6 cabbage/15 LBF). All the herbicide treatments except the glyphosate tank-mixes (10.6 to 12.1 cabbage /15 LBF) contained a greater number of cabbages than the untreated check (10.25 cabbage/15 LBF). Cabbage survival was low in the untreated plots because of excessive unmanaged weed competition for resources such as sunlight, water, and nutrients. Allelopathic chemicals produced by the weeds may have also been a fa ctor that resulted in the decline of stand establishment. Frequent cultivation could have disturbed cabbage roots which had a direct effect

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187 on water and nutrient uptake. In addition, cultivation may have slightly injured cabbage roots which led to increased susceptibility to soil bo rne pathogens that indir ectly led to decreased water and nutrient uptake. An explanation for the decreased establishment in the plots treated with glyphosate plus s-metolachlor in the fallow period is uncertain. External factors such as fertilizer toxicity and lateral herbicide movement may have led to the decline in cabbage numbers. Fertilizer wa s applied by hand which was not the most accurate and uniform method of distribution. On one occa sion when the fertilizer was applied the soil was moist which made the fertilizer dissolve ho wever irrigation was not provided to dilute the granular fertilizer until several days later therefor e the fertilizer was more too concentrated. The pre-plant herbicide labels warn against stressing the transplants by drought or over fertilization to avoid herbicide toxicity and possible death. In addition, the field had a s light slope which would cause overhead irrigation wa ter to pool more on one side of the field. This side of the field had less vigorous cabbage, however it is unclear whet her the plants suffered from over irrigation or chemicals dissolved in the irrigation water whic h accumulated there in greater amounts. Total Cabbage Weight Fallow treatment effect: The total cabbage weight was highe st in the plots treated with glyphosate (47 lbs/15 LBF), glyphosate plus s-metol achlor (41 lbs/ 15 LBF), and all the paraquat treatments (> 43 lbs/15 LBF) (Figure 2-62). The total we ight was significantly higher in all the paraquat treatments (> 43 lbs/ 15 LBF), and glyphosate alone (47 lbs/15 LBF) when compared to the untreated (30 lbs/15 LBF) and cultivated chec ks (33 lbs/15 LBF). In addition, glyphosate alone (47 lbs / 15 LBF) and paraqua t tank-mixed with s-metolachlor (50 lbs/ 15 LBF) resulted in higher total cabbage yields th an glyphosate plus trifloxysul furon (37 lbs/ 15 LBF). It is not known why trifloxysulfuron reduced cabbage yield when added to glyphosate but not paraquat. External factors may be involve d. Additional studies should be conducted to

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188 verify these results. However, most of the herb icides used during the fallow period increased the yield of cabbage compared to the untreated control, which was the one of the main goals of this experiment. In addition, all of the paraqua t treatments and glyphosate alone increased cabbage total yield compared to the cultivated check. This indi cates that two herbicide applications during the summer results in a higher yield level than fr equent season long tillage. Herbicides do not disturb the soil and the crop roots wh ich may have lead to the increa se in total yields. Pre-plant herbicide application and planting was done on th e same day for all the plots. However, cultivation did not begin until two weeks after planting, which may have allowed early weed competition to occur and ultimately result in lowe r cabbage yields. Meanwhile, the plots treated with herbicides during the fallow period had the lowest weed infe station at planting. Average Cabbage Weight Fallow treatment effect: Cabbage average weight was highe st in the plots treated with glyphosate (3.8 lbs/head), glyphosate plus s-me tolachlor (4 lbs/head), paraquat plus smetolachlor (3.9 lbs/head) and paraquat alone (3.5 lbs/head) (Figure 2-63). The treatments that resulted in the lowest cabbage average weights were the untreated check (3 lbs/head), glyphosate plus trifloxysulfuron (3 lbs/head), paraquat plus trifloxysulfuron (3.3 lbs/ head), paraquat alone (3.5 lbs/head) and the cultivated check (3 lbs/head ). Average cabbage weights were higher in the glyphosate plus s-metolachlor treated plots compar ed to the plots treated with glyphosate plus trifloxysulfuron, paraquat tank-mixed with tr ifloxysulfuron, the cult ivated check and the untreated check. In addition, glyphosate alone a nd paraquat plus s-metolachlor yielded larger cabbages than the untreated ch eck, glyphosate plus trifloxysulfu ron, and the cultivated check. S-metolachlor used during the fallow increased the weight of the average cabbage when added to either paraquat or glyphosate, al though not significantly. Since paraquat and

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189 glyphosate only control emerged weeds the addition of pre-plant herbicide applied in the fallow season increases the overall level and spectrum of weed control. When added to glyphosate or paraquat, trifloxysulfuron also in creased the overall level and spect rum of weed control, however trifloxysulfuron may also cause slight stunti ng which is why the vigo r and average cabbage weight is slightly lower, however not signifi cantly. In contrast, trifloxysulfuron did not adversely affect the number of cabbage produced which means the herbicide toxicity did not result in cabbage death but possibly stunting. Total Cabbage Weight Pre-plant treatment effect: Overall, cabbage yields were significantly higher in the oxyfluorfen (44 lbs/15 L BF) treated plots compared to the ones treated with s-metolachlor (38 lbs/15 LBF), when averaged across all fallow treatm ent plots (Figure 2-64). Broadleaf and grass weeds are commonly more competitive with crops th an sedges at low infestation numbers. In general, oxyfluorfen provided superior control of broadleaf and gra ss weeds during the crop compared to s-metolachlor. Fallow weed cont rol methods should be implemented to control various weeds, especially purple nutsedge. Preplant herbicides should be used to treat the remaining weeds that escape fallow control and pose an infestation threat to the crop. Average Cabbage Weight Pre-plant treatment effect: The average weigh t per cabbage was significantly higher in oxyfluorfen (3.8 lbs/head) treated plots than s-metolachlor (3.1 lbs/he ad) (Figure 2-65). Similarly to total yield the oxyfluorfen treated plots resulted in bigger cabbages. Oxyfluorfen controlled broadleaf and grass weeds better than s-metolachlor, therefore the cabbages were allowed to grow with less competition which yielded bigger plants. Although oxyfluorfen did not control purple nutsedge as well as s-metolachlor, the fallow treatments primarily controlled

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190 purple nutsedge whereas the pre-pl ant herbicides primarily controlled sexually propagated weeds that emerged following the disturbance caused by field preparation. Weeds after Cabbage Harvest Purple nutsedge post cabbage harvest After the cabbage was harvested and all the pl o ts were cultivated, th ere were significant differences in weed control between treatments. All the herbicides (> 70.6 % control) except glyphosate tank-mixed with s-metolachlor (55 % control) provided the best purple nutsedge control (Figure 2-66). These herbicides (> 70.6 % control) controll ed purple nutsedge significantly better than glyphosate plus s-metolachlor (55 % control) and the untreated check (15.6 % control). Trifloxysulfuron tank mixed with either glyphosate or pa raquat (80 % control) and paraquat plus s-metolachlor ( 81 % control) gave significantly higher purple nutsedge control than cultivation alone (62.5 % c ontrol). All the treatments (> 55 % control) provided significantly better nutsedge control compared to the untreated check. The effects of fallow weed control treatments ar e beneficial during the fallow, the crop and even after the fall crop into the spring crop. Applying he rbicides during the summer fallow season decreased purple nutsedge more than bi weekly hand hoeing implemented throughout the fall cropping season. Hand hoeing has a short te rm effect on nutsedge control. Cultivation controls nutsedge shortly after it is performed however, once cult ivation has ceased nutsedge is able to re-establish itself and begin to pro liferate. A speculative reason to explain why smetolachlor (mixed with glyphosate) increased pu rple nutsedge control during the fallow period, during the beginning of the cropping season but not toward the end of the crop and after the crop is that s-metolachlor only provides temporary pur ple nutsedge control. S-metolachlor might hinder root and shoot growth from viable tubers but not kill the tube r completely. If s-

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191 metolachlor delays shoot emergence until after glyphosate is applied then glyphosate will not be absorbed, translocated within the pl ant, and control the underground tubers. Crabgrass post cabbage harvest There were significan t differences in crabgr ass control between treatments following the cabbage harvest. All the herbicides (> 66 % c ontrol) used in this st udy controlled crabgrass better than hand-hoeing (33 % cont rol) and the untreated check af ter the crop (Figure 2-67). In addition, the cultivated check (33 % control) provided higher crabgr ass control than the untreated check but not as much as the diffe rent herbicides (> 66 % control). Although cultivation provided excellent cra bgrass control during the crop, it did not provide long term crabgrass contro l. In contrast, the herbicides used provided long term control of crabgrass. The fallow herbicides controlled the crabgrass plants and germination seedlings during the summer. In addition, the herbicides prevented crabgrass from producing seeds and depositing them into the soil profile. Although cu ltivation during the crop did prevent the plants present from producing seeds, the main grow th season of crabgrass is in the warmer temperatures of the late spring, summer, and early fall. Once temperatures become low, seeds become dormant and do not germinate. Therefore, summer fallow treatments targeted the optimal crabgrass growing season when seeds ar e produced. Cultivation during the summer does result in a flush of crabgrass, which can then be killed by herbicides or subsequent tillage. However, fully mature crabgrass plants are to tally controlled during summer cultivation, because the soil is moist and plant fragments become propagative material. Pusley post cabbage harvest Florida Pusley was controlled best by cultiv ating (88 % control) during the growing season and by all th e fallow applied herbicides (> 70 % control) except for paraquat alone (51 % control) after the cabbage had been harvested (Fi gure 2-68). All the treatm ents (> 51 % control)

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192 controlled pusley to a greater extent than the untreated check. Glyphosat e alone (80 % control), paraquat tank mixed with trifloxysulfuron (84 % control), and cultivation (88 % control) controlled pusley significantly better than paraquat alon e (51 % control). Implementation of all the proactive fallow treat ments resulted in dramatically increased Florida Pusley control compared to leaving th e field unattended. Cultivating, glyphosate, and all the tank mixes with pre-plant herbicides provided excellent long term control of Florida Pusley by destroying the plants, theref ore preventing them from produc ing viable seeds. However, paraquat is a contact herbicide that did not kill the shoot meristem of pusley, thus it was able to re-grow and produce seeds after being treated. Purslane post cabbage harvest All the trea tments (> 27.5 % control) except paraquat plus s-metolachlor (17.5 % control) controlled purslane significantly better than th e untreated check (Figure 2-69). The cultivated check (27.5 % control) a nd all the herbicides (> 33.75 % control) ex cept paraquat plus smetolachlor (17.5 % control) provided the highest degree of purslane control following in the fallow period after cabbage harvest. Glyphos ate plus s-metolachlor (52.5 % control) and paraquat alone (44 % control) c ontrolled purslane significantly better than paraquat plus smetolachlor (17.5 % control). Most of the fallow treatments had a positive impact on carryover purslane control after cabbage was harvested. However, an explanation for the decreased control response obtained in the paraquat plus s-metolachlor in not clear. Perhaps this should be further investigated to determine if this response is reproduci ble and provide clarity on the matter.

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193 Conclusions Fallow Treatments Untreated fallow The untreated fallow treatm ent did not control any weeds. The weeds were left unmanaged and allowed to grow unchecked. We eds in the untreated fallow proliferated via seeds and vegetative parts. Leaving the fiel d unattended during the fallow period allowed the weeds to become more numerous and nega tively impacted subsequent crop growth, development, and yield through increased competition for vital resources. Cultivation Cultiva tion controlled the weeds better than the untreated check, when cultivation was performed. However, cultivation had no pre-emergent or residual weed control. Weed infestation levels quickly reached their original levels when the land was left undisturbed. In many cases tillage increased weed counts of pioneer species, which are the first to colonize disturbed areas, because competition from other weeds was removed. Cultivation does prevent plants from forming seeds and depletes the soil seed bank reserves. Tilla ge plays a crucial role in inducing seeds to germinate and provides a prime opportunity for targeting seedlings with herbicides. Seedlings are most susceptible growth stage and are most effectively controlled with herbicides since they are young, tender, and f eeble. Cultivation controlled purple nutsedge compared to the untreated check. Frequent cultivation under dry soil conditions, depleted carbohydrate reserves in the tuber and caused the tubers to de siccate rather than reestablishing themselves. Hand-hoeing biweekly during the cr op provided excellent tem porary control of all weeds, however cabbage vigor, stand establishment, plant size, and total yield suffered compared to the best fallow herbicide treatments. Cultiva tion disturbs the soil, which may have damaged

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194 cabbage roots, therefore hindering crop growt h. Using pre-plant herb icides during the crop resulted in similar yields in the cultiv ated and untreated plots fallow plots. Glyphosate Fallow applications of glyphosate provided post em ergent control of all of the weeds present when it was applied. The full impact of glyphosate on the plant was not immediate. A few weeks were needed to realize the full extent of glyphosat e control. Glyphosate did not provide any pre-emergent or re sidual weed activity. This herbicide provided temporary and long term control of purple and yellow nutsedge because it killed the underground tubers of the plant. Multiple applications were needed to control purple nutsedge. In addition, the efficacy of glyphosate was dependent on weed species and environmental conditions. Glyphosate lowered the amount of seed rain produced by sexually re producing plants which had a direct impact on the soil seed bank. The populations of subseque nt weed populations were lowered compared to the untreated check due to the lowered weed pressure. Applications made to weeds during drought stress conditions reduced the efficacy of glyphosate considerably. Glyphosate provided long term control of weeds during the crop afte r the fallow period and ev en after the crop was removed the effects could still be clearly obs erved. Although fallow applications of glyphosate is effective at controlling nutsedges during the cropping season, a pre-pl ant herbicide should be used during the crop to provide enhanced control of broadleaf and grass weeds. Lastly, fallow glyphosate applications resulted in increased crop yields compar ed to the untreated check, and did not cause herbicide toxicity in cabbage. Glyphosate plus s-metolachlor Applying a m ixture of glyphosate and s-metolachlor provided a synergistic effect on weed control in most species. In addition, to the post emergent control provided by glyphosate, smetolachlor gave beneficial pre-emergent contro l of many weeds including sedges, broadleaves,

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195 and grasses. Residual weed control was not pr ovided by s-metolachlor. S-metolachlor tankmixed with glyphosate did not hinder crop grow th and yields. Although this combination controlled many weeds during the fall ow season, pre-plant herbicides should be used to increase weed control during the crop. Glyphosate plus trifloxysulfuron Glyphosate tank m ixed with trif loxysulfuron provided exce llent broad spectrum weed control during the fallow period. Trifloxysul furon mixed with glyphosate provided post emergent, pre-emergent, and resi dual control of sedge and broa dleaf weeds. Post emergent control of grasses was provided by this herbicide mixtur e. The residual control of sedges and broadleaf could be observed by the high level of weed suppression following tillage events. The glyphosate alone and glyphosate ta nk mixed with s-metolachlor did not continue to provide effective control of weeds, especially annual br oadleaf weeds after cultivation. Trifloxysulfuron plus glyphosate permanently stunted nutsedge plants after treatments were applied. In addition, trifloxysulfuron mixed with paraquat revealed sim ilar residual control prop erties. These results indicate that trifloxysulfuron provi ded the residual control in thes e mixtures and is an important compound for providing residual co ntrol of sedge and broadleaf weeds during the fallow season. Vigor or yield differences between treatments were not observed in the corn crop planted after the first year of fallowing. Unfortuna tely, fallow applications of glyphosate plus trifloxysulfuron may have slightly decreased cabbage vigor, size, a nd total yield compared to the most promising fallow herbicide treatments but not compared to the untreated or cultivated check. Corn is less sensitive to trifloxysulfuron toxicity than cabbage. In addition, the corn was planted in spring following the fallow treatments, while the cabbage was planted in the fall directly after the summer fallow. In the corn crop, the longer layover period may have allowed the herbicide to degraded and nullify the toxic e ffects observed in cabbage. Lastly, corn is a grass

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196 crop and trifloxysulfuron does not provide residual control of grass weeds, which would explain the response of corn to this particular herbicide. Paraquat Typically contact herbicides like paraquat do not control weeds as well as system ic herbicides like glyphosate and tr ifloxysulfuron. Paraquat is not absorbed into the plant and translocated to the actively growi ng portions of the plant. Thus, it is unable to effectively control underground structures such as tubers, and meri stems that are covered by plant canopies, which is typical with older grasses, sedges, and broa dleaves. However, in the current experiment, consisting of multiple sequential paraquat app lications with tillage implemented between herbicide applications, paraqua t was able provide post emergent control of nutsedges, broadleaves, and grasses. Init ial applications of paraquat bur ned down large weeds that were present at the beginning of the fallow season, however many were not killed. Many weeds were able to re-sprout from tubers, and shielded above ground shoot meristem. However, this application depleted the weed s of carbohydrate reserves and prevented them from developing seeds or producing new underground propagative st ructures, such as tubers. Tillage destroyed most of the existing broadleaf, and grass weeds, es pecially since they were already in a weaken state. Tillage also destroyed nutsedge shoots, ca using them to re-sprout from tubers. The second application of paraquat was able to kill most of the weeds because unlike before they were small, tender, exposed, and vulnerable to control with paraquat. During the second applic ation paraquat was able to destroy weeds including purple nuts edge and grasses, because the exposed shoot meristem of the small plants were penetrated by the spray due to the lack of canopy cover. Continuing with two spray applica tions, two cultivation events for two consecutive years enabled successful weed control for almost all species by continually depleti ng carbohydrate reserves,

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197 preventing seed rain, depleting the soil seed ba nk, and killing small plants. Paraquat did not provide any pre-emergent or re sidual control of weeds. No yield differences in yield or vigor between fallow treatments were noticed in corn. Applying paraquat during the summer fallow in c onjunction with pre-plant herbicides during the cropping season provided the highest level of cabbage vigor, stand establishment, size, and yield. Cabbage is less competitive than corn; theref ore weed infestations have a more pronounced negative effect on cabbage yield. Paraquat plus s-metolachlor The addition of smetolachlo r to paraquat provided pre-em ergent weed control activity which does not occur with paraquat alone. Theref ore, these herbicides were complimentary to each other because they provided weed control to existing plants and emerging seedlings, which broadened the spectrum of weed control possibilities that either herbicide could not provide alone. However, this herbicide combination did not provide any l ong term residual weed control. Paraquat plus s-metolachlor resulted in the highest level of vigor, stand establishment, fruit size, and yield in cabbage and corn. Paraquat plus trifloxysulfuron Trifloxysulf uron mixed with paraquat gave excellent post emergent control of sedges, grasses, and broadleaves when applied. Pre-emer gent and residual control of broadleaves and sedges were achieved using paraqua t plus trifloxysulfuron. Howeve r, these herbicides did not provide pre-emergent or residual control of grasses. Cabbage vigor, stand establishment, and to tal yield were very high when using these herbicides during the fallow period. However, cabbage size may ha ve suffered slightly.

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198 Pre-plant Herbicide Treatments Oxyfluorfen Oxyfluorfen provided better weed control of broadleaf and gra ss species. In addition, the use of oxyfluorfen resulted in greater cabbage yi elds. Oxyfluorfen did not control nutsedges as well as s-m etolachlor, however, nutsedge control was mainly a factor of fallow herbicide treatments rather than pre-plant herbicide treatments. S-metolachlor As a pre-pla nt herbicide treatment s-meto lachlor controlled nutsedges better than oxyfluorfen. However, s-metolachlor did not co ntrol broadleaf and grass weeds well compared to oxyfluorfen. S-metolachlor resulted in lower cabbage yields than oxyfluorfen. Pre-emergent herbicides used in conjunction with fallow herb icide treatments need to control annual grass and broadleaf weeds rather than nutse dges since long term control of nutsedge is provided primarily by fallow herbicide treatments.

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199 0 10 20 30 40 50 60 70 80 90 100 9/12/0610/19/0611/9/064/11/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-1. Effect of differen t fallow treatments on the contro l of purple nutsedge during the first fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was only performed in the cultivation treatment plots during the fallow period and no cultivati on was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

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200 dacc bc a ab ab bc a b a abc a b a abc a ab ab a a a a c a b b ab a c ab 0 20 40 60 80 100 9/12/200610/19/200611/9/20064/11/2007 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-2. Effect of differen t fallow treatments on the contro l of purple nutsedge during the first fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly diffe rent according to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis stunting, or death. Cultivation was only performed in the cult ivation treatment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

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201 0 20 40 60 80 100 8/14/078/27/079/14/079/28/07 Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-3. Effect of differen t fallow treatments on the contro l of purple nutsedge during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

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202 abdc a ab cd bc a a bc ab a a a a a a ab ab a a a a a ab ab ab a bdc 0 10 20 30 40 50 60 70 80 90 100 8/14/078/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-4. Effect of differen t fallow treatments on the contro l of purple nutsedge during the second fallow season in Citra, Fl. Mean s followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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203 0 100 200 300 400 500 8/27/07 9/14/07 9/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-5. Effect of differen t fallow treatments on the populat ion density of purple nutsedge during the second fallow season in Citra, Fl. Weed count s include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the sec ond crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 204

204 a a a a a b a a b a a b a a b a a b a a b a a ab 0 50 100 150 200 250 300 350 400 450 8/27/079/14/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-6. Effect of differen t fallow treatments on the populat ion density of purple nutsedge during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly ba sis in the second crop.

PAGE 205

205 0 20 40 60 80 100 120 8/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-7. Effect of differen t fallow treatments on the contro l of yellow nutsedge during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 206

206 bbc a a ab a ab a a a a a ab a a a b b ab bbc 0 20 40 60 80 100 120 8/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-8. Effect of differen t fallow treatments on the contro l of yellow nutsedge during the second fallow season in Citra, Fl. Mean s followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

PAGE 207

207 0 10 20 30 40 50 60 08/28/07 09/13/07 09/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-9. Effect of differen t fallow treatments on the populat ion density of yellow nutsedge during the second fallow season in Citra, Fl. Weed count s include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 208

208 a a a a a b a a b aab a ab a a b a a b a a ab 0 10 20 30 40 50 60 08/28/0709/13/0709/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-10. Effect of different fallow treatme nts on the population density of yellow nutsedge during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 209

209 c a a a a ab ab b 0 10 20 30 40 50 60 70 80 90 100 4/11/07 Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-11. Effect of different fallow treatme nts on the control of la rge crabgra ss during the first fallow season in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cultivation trea tment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Herbicide and Cultivation Crop

PAGE 210

210 0 20 40 60 80 100 120 8/14/078/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-12. Effect of different fallow treatme nts on the control of la rge crabgra ss during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 211

211 abbb a a b a a a a a a a b a a a a a a a ab a a a aa b a bb 0 20 40 60 80 100 120 8/14/078/27/079/14/079/28/07Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-13. Effect of different fallow treatme nts on the control of la rge crabgra ss during the second fallow season in Citra, Fl. Mean s followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis date s and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 212

212 0 20 40 60 80 100 120 140 8/28/079/13/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-14. Effect of different fallow treatme nts on the population dens ity of large crabgrass during the second fallow season in Citra, Fl. Weed count s include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 213

213 abc ab bc abc c bc bc a 0 5 10 15 20 25 30 8/28/07 DateCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-15. Effect of different fallow treatme nts on the population dens ity of large crabgrass during the second fallow season in Citra, Fl. Means follo wed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plan ts independent of visual health. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivat ion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 214

214 0 20 40 60 80 100 120 9/12/0610/19/0611/9/06 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-16. Effect of different fallow treatme nts on the control of goosegrass during the first fallow season in Citra, Fl. Control is defi ned as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cultivation treatm ent plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 215

215 dcb b ab a a a a ab b a a ab a ab ab a ab ab a c ab b 0 20 40 60 80 100 120 9/12/0610/19/0611/9/06 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-17. Effect of different fallow treatme nts on the control of goosegrass during the first fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cult ivation treatment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 216

216 b aaaaaa b 0 20 40 60 80 100 120 9/28/07 Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-18. Effect of different fallow treatme nts on the control of goosegrass during the second fallow season in Citra, Fl. Means follow ed by the same letter are not significantly different according to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, st unting, or death. Cul tivation was performed to all treatments plots during the fall ow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applica tions timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 217

217 a b bbbbb a 0 5 10 15 20 25 30 9/28/07DateCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-19. Effect of different fallow treatme nts on the population density of goosegrass during the second fallow season in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include all living plants i ndependent of visual health. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applica tions timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 218

218 0 10 20 30 40 50 60 70 80 90 8/14/07 8/27/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-20. Effect of different fallow treatment s on the control of volunteer corn plants during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 219

219 b a a a a a a a a a a a a a b a 0 10 20 30 40 50 60 70 80 90 08/14/07 08/27/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-21. Effect of different fallow treatment s on the control of volunteer corn plants during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis date s and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 220

220 b aaaaaa b 0 20 40 60 80 100 120 9/28/2007 Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-22. Effect of different fallow treatment s on the control of crowfootgrass plants during the second fallow season in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applica tions timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 221

221 0 20 40 60 80 100 120 9/12/0610/19/0611/9/064/11/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-23. Effect of different fallow treatme nts on the control of amaranth during the first fallow season in Citra, Fl. Control is defi ned as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cultivation treatm ent plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 222

222 cebb b abc a a a cd a a a a a a a cd a a a ab a a ab de a a b bcd b a 0 20 40 60 80 100 120 9/12/0610/19/0611/9/064/11/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-24. Effect of different fallow treatme nts on the control of amaranth during the first fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cult ivation treatment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 223

223 0 20 40 60 80 100 120 8/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-25. Effect of different fallow treatment s on the control of amaranth plants during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 224

224 bbb a b a a b a aaa a b a a aa a b a bbb 0 20 40 60 80 100 120 8/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-26. Effect of different fallow treatment s on the control of amaranth plants during the second fallow season in Citra, Fl. Mean s followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis date s and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 225

225 0 50 100 150 200 250 8/28/079/13/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-27. Effect of different fallow treatme nts on the population density of amaranth during the second fallow season in Citra, Fl. Weed counts include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 226

226 a a ab a a b a a b a a b a a b a a b a a b a a a 0 50 100 150 200 250 8/28/079/13/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-28. Effect of different fallow treatme nts on the population density of amaranth during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plan ts independent of visual health. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 227

227 0 20 40 60 80 100 120 9/12/0610/19/0611/9/06 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-29. Effect of different fallow treatme nts on the control of common purslane during the first fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was only performed in the cultivation treatment plots during the fallow period and no cultivati on was implemented during the growing season. Note x axis dates and treatment applic ations timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 228

228 b d c a cd b a bc a a a aa bc aa ab ab a bc ab b bc b 0 20 40 60 80 100 120 9/12/06 10/19/06 11/9/06 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-30. Effect of different fallow treatme nts on the control of common purslane during the first fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly diffe rent according to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis stunting, or death. Cultivation was only performed in the cult ivation treatment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 229

229 0 20 40 60 80 100 120 8/14/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-31. Effect of different fallow treatme nts on the control of purslane plants during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 230

230 abb ab a a b a a aa ab a a aa a b a abb 0 20 40 60 80 100 120 8/14/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-32. Effect of different fallow treatme nts on the control of purslane plants during the second fallow season in Citra, Fl. Mean s followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis date s and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 231

231 0 50 100 150 200 250 300 350 9/14/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-33. Effect of different fallow treatme nts on the population density of purslane during the second fallow season in Citra, Fl. Weed counts include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 232

232 b b bb b b b a 0 20 40 60 80 100 120 9/28/07 DateCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-34. Effect of different fallow treatme nts on the population density of purslane during the second fallow season in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Weed counts include all living plants i ndependent of visual health. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applica tions timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 233

233 b a a a a a a a 0 10 20 30 40 50 60 70 80 90 100 4/11/07 Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-35. Effect of different fallow treatment s on the control of Florida pusley during the first fallow season in Citra, Fl. Means fo llowed by the same letter date are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cultivation trea tment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 234

234 0 20 40 60 80 100 120 9/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-36. Effect of different fallow treatment s on the control of Florida pusley plants during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 235

235 db cd a bc a ab a cd a aa d a db 0 20 40 60 80 100 120 9/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-37. Effect of different fallow treatment s on the control of Florida pusley plants during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis date s and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 236

236 0 5 10 15 20 25 9/13/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-38. Effect of different fallow treatme nts on the population density of Florida pusley during the second fallow season in Citra, Fl. Weed count s include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 237

237 d ab a a abab bc c 0 20 40 60 80 100 120 4/11/07 Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-39. Effect of different fallow treatments on the control of cutleaf evening primrose during the first fallow season in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was only performed in the cultivation trea tment plots during the fallow period and no cultivation was implemented during the growing season. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 238

238 0 20 40 60 80 100 120 8/14/078/27/079/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-40. Effect of different fallow treatment s on the control of cutleaf ground cherry plants during the second fallow season in Citra, Fl. Control is de fined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 239

239 bcbb ab b a a a b a a a aa a a b a a aaa a a b a b cbb 0 20 40 60 80 100 120 8/14/078/27/079/14/079/28/07Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-41. Effect of different fallow treatment s on the control of cutleaf ground cherry plants during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 240

240 0 10 20 30 40 50 60 8/14/078/28/079/13/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-42. Effect of different fallow treat ments on the population de nsity of cutleaf ground cherry during the second fallow season in Citra, Fl. Weed counts include all living plants independent of visual health. Cultiv ation was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 241

241 a a a b b a b b a b b a b b a b b a b b a b b a 0 10 20 30 40 50 60 8/28/07 9/13/07 9/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-43. Effect of different fallow treat ments on the population de nsity of cutleaf ground cherry during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not signifi cantly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 242

242 0 20 40 60 80 100 120 9/14/079/28/07 Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-44. Effect of different fallow treatments on the control of carpet weed plants during the second fallow season in Citra, Fl. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 243

243 bb b a b a aa b a aa b a bb 0 20 40 60 80 100 120 9/14/079/28/07Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-45. Effect of different fallow treatment s on the control of carpe tweed plants during the second fallow season in Citra, Fl. Mean s followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis date s and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

PAGE 244

244 0 10 20 30 40 9/13/079/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-46. Effect of different fallow treat ments on the population density of carpetweed during the second fallow season in Citra, Fl. Weed count s include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

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245 a a a b a b a b a b a b a b a a 0 5 10 15 20 25 30 35 40 9/13/07 9/28/07 DatesCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-47. Effect of different fallow treat ments on the population density of carpetweed during the second fallow season in Citra, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Weed counts include all living plants independent of visual health. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoei ng was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applications timelines are not drawn to scale. Cultivation Herbicide Crop

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246 b aaaaaa b 0 20 40 60 80 100 120 9/28/07Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-48. Effect of different fallow treatme nts on the control of redweed plants during the second fallow season in Citra, Fl. Means fo llowed by the same letter not significantly different according to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, st unting, or death. Cul tivation was performed to all treatments plots during the fall ow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop. Note x axis dates and treatment applica tions timelines are not drawn to scale. Cultivation Herbicide Crop

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247 d cb bc ab a abc b a ab ab a a ab a abc ab a ab ab a c a a 0 10 20 30 40 50 60 70 80 90 100 123 Sampling Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-49. Effect of different fallow treatments on the control of purple nutsedge plants during the second crop season (cabbage) in Citra, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivati on was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop.

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248 a b b a a a 0 10 20 30 40 50 60 70 80 90 123 Sampling Dates% Control Oxy S-Met Figure 2-50. Effect of different pre-plant herb icide treatments on the c ontrol of purple nutsedge plants during the second crop season in C itra, Fl. Means followed by the same letter within a sampling date are not significan tly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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249 d b a ab a ab ab c 0 20 40 60 80 100 120 1 Sampling Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-51. Effect of different fallow treat ments on the control of yellow nutsedge plants during the second crop season in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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250 c c ab ab ab ab b ab ab ab b b b ab a a 0 20 40 60 80 100 120 23 Sampling Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-52. Effect of different fallow treatment s on the control of crab grass plants during the second crop season in Citra, Fl. Means follo wed by the same letter within a sampling date are not significantly diffe rent according to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivat ion treatment on a biweekly basis in the second crop.

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251 a a b b 0 10 20 30 40 50 60 70 80 90 100 23 Sampling Dates% Control Oxy S-Met Figure 2-53. Effect of different pre-plant herbic ide treatments on the control of crabgrass plants during the second crop season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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252 a b 0 20 40 60 80 100 120 3 Sampling Date% Control Oxy S-Met Figure 2-54. Effect of different pre-plant herbic ide treatments on the control of cutleaf evening primrose plants during the second crop s eason in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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253 ab ab c abc bc bc bc abc c bc bc c bc bc a a 0 20 40 60 80 100 120 23 Sampling Dates% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-55. Effect of different fallow treatme nts on the control of purslane plants during the second crop season in Citra, Fl. Means follo wed by the same letter within a sampling date are not significantly diffe rent according to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivat ion treatment on a biweekly basis in the second crop.

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254 a a b b 0 20 40 60 80 100 120 23 Sampling Dates% Control Oxy S-Met Figure 2-56. Effect of different pre-plant herbic ide treatments on the control of purslane plants during the second crop season in Citra, Fl. Means followed by the same letter within a sampling date are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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255 a b b b b b b b 0 50 100 150 200 250 1 Sampling DateCounts/m2 Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-57. Effect of different fallow treatme nts on the population density of purple nutsedge plants during the second crop season in C itra, Fl. Means followed by the same letter are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivat ion treatment on a biweekly basis in the second crop.

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256 a b 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 Sampling DateCounts/m2 Oxy S-Met Figure 2-58. Effect of different pre-plant he rbicide treatments on the population density of yellow nutsedge plants during the second cr op season in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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257 b a 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 1 Sampling DateCounts/m2 Oxy S-Met Figure 2-59. Effect of different pre-plant herb icide treatments on the population density of large crabgrass plants during the second crop seas on in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death.

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258 d ab abc bcd a ab abc cd 0 10 20 30 40 50 60 70 80 90 100 1 Sampling Date% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-60. Effect of different fallow treat ments on cabbage vigor during the second crop season in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Di fference test at P = 0.05. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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259 d abc cd abcd ab a ab bcd 0 2 4 6 8 10 12 14 NumberCabbage/15 LBF Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-61. Effect of different fallow treat ments on cabbage stand establishment during the second crop season in Citra, Fl. Mean s followed by the same letter are not significantly different accordi ng to Fishers Least Signifi cant Difference test at P = 0.05. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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260 d a abc bcd a ab ab cd 0 10 20 30 40 50 60 TotalLbs/plot Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-62. Effect of different fallow treatments on total cabbage weight per plot (15 LBF of row) during the second crop season in Citra, Fl. Means followed by the same letter are not significantly different according to Fi shers Least Significant Difference test at P = 0.05. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultiva tion treatment on a biweekly basis in the second crop.

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261 c ab a c ab bc abc c 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 AveLbs/cabbage Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-63. Effect of different fallow treatments on average cabbage weight during the second crop season in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Si gnificant Difference test at P = 0.05. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivat ion treatment on a biweekly basis in the second crop.

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262 a b 35 36 37 38 39 40 41 42 43 44 45 TotalLbs/plot Oxy S-Met Figure 2-64. Effect of different pre-plant herbic ide treatments on total cab bage weight per plot (15 LBF of row) during the second crop seas on in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05.

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263 a b 0 0.5 1 1.5 2 2.5 3 3.5 4 AveLbs/Cabbage Oxy S-Met Figure 2-65. Effect of different pre-plant herb icide treatments on aver age cabbage weight per plot (15 LBF of row) during the second cr op season in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05.

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264 d ab c a a a ab bc 0 10 20 30 40 50 60 70 80 90 Purple% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-66. Effect of different summer fallo w treatments on the long term control of purple nutsedge after the harvest of the second crop in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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265 c a a a a a a b 0 10 20 30 40 50 60 70 80 90 100 Crab% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-67. Effect of different summer fallo w treatments on the long term control of large crabgrass after the harvest of the second crop in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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266 c a abab ab a b a 0 10 20 30 40 50 60 70 80 90 100 Pusley% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-68. Effect of different summer fallow treatments on the long term control of Florida pusley after the harves t of the second crop in Citra, Fl. Means followed by the same letter are not significantly different accordi ng to Fishers Least Significant Difference test at P = 0.05. Control is defined as pl ant chlorosis, necrosis stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivat ion treatment on a biweekly basis in the second crop.

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267 c ab a ab bc ab a ab 0 10 20 30 40 50 60 Purslane% Control Untreated Gly + Gly Gly & S-Met + Gly Gly & Tri + Gly Para & S-Met + Para Para & Tri + Para Para + Para Cultivation Figure 2-69. Effect of different summer fallo w treatments on the long term control of common purslane after the harvest of the second cr op in Citra, Fl. Means followed by the same letter are not significantly different according to Fishers Least Significant Difference test at P = 0.05. Control is defined as plant chlorosis, necrosis, stunting, or death. Cultivation was performed to all treatments plots during the fallow period, however, hand hoeing was implemented to the cultivation treatment on a biweekly basis in the second crop.

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268 CHAPTER 4 CONCLUSIONS LIVE OAK AND CITRA SUMMARY Untreated Fallow Effect on Weeds In general, fallow fields left unattended between production cycl es resulted in higher weed inf estation compared to all other treatments. These results were observed for yellow nutsedge, Florida pusley and large crabgrass in Live Oak. In Citra, this pattern was continued for all weeds observed during the fallow period. Live Oak Purple nutsedge and carpetweed counts in untre a ted plots were lower than the cultivated check in Live Oak. The untreated check contained less purple nutsedge than the cultivated check, but the herbicide treate d plots contained the least am ount of nutsedge. A possible explanation is cultivation ma y have caused dormant tubers to sprout by breaking apical dominance in purple nutsedge tuber chains. In addition, cultivation may cau se a shift in species due to lower competition from more vigorous we ed species and allow nutsedge a chance to proliferate. Carpetweed counts were lower in the untreated plots compared to the cultivated check and glyphosate plus cultivation after cultivation was implemented. Carpetweed is a pioneer rudimentary species that may take advantage of soil disturbance, which may explain why cultivation increases carpetweed number s compared to the untreated check. Citra All the weed s were higher in the untreated plots compared to the cultivated check in Citra, except purslane. The untreated check contained less purslane than the cultivated check. Similar to carpetweed, purslane is a weed species that colonizes disturbed areas, which may account for the increased numbers in the cultivated checks.

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269 Effect of Fallow Cultivation on Weeds (Regardless of Herb icides) Live Oak Cultiva tion may cause an increase flush of s eedlings when it is initially implemented. However, the effect of multiple cultivation even ts over a two year period generally decreases the amount of weeds in the field rega rdless of herbicide applications. The effect of cultivation on pusley counts varied overtime. Initially cultivat ion caused an increase in the pusley population. This increase in seedling emergence was probably due to the soil disturba nce which released the seeds from dormancy and caused sprouting. Ho wever, by the beginning of the second fallow season, cultivated plots had less pusley than non-cultivated plots. Multiple sequential tillage events seemed to deplete the soil seed reserv es and prevent plants from maturing to seed production capacity. Fallow Cultivation Effect on Weeds In general, cultiv ation alone resulted in lo wer weed counts than th e untreated check and higher weed counts than the treatments that contained herbicides for most weed species. This was the case observed for Florida pusley and crabgrass (depending when cultivation was implemented) in Live Oak. In Citra, this tr end was observed during the first year for purple nutsedge, crabgrass, amaranth, purslane, Florid a pusley, and cutleaf eveningprimrose. During the second year this trend was observed for purpl e nutsedge and cutleaf ground cherry counts. However, there were some weeds that did no t follow this general pattern. During the fallow period the cultivated check contained th e highest number of purpl e nutsedge compared to all other treatment plots in Live Oak. Cultiva tion provided similar yellow nutsedge control as the herbicide treatments, which was better than th e untreated check. Cult ivation and cultivation plus glyphosate resulted in the highest number of carpetweed after cultivation was implemented. In Citra, cultivation did not increase the contro l of yellow nutsedge for both years of the study, but crabgrass, amaranth, Florida pusley, and car petweed were controlled during the second year

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270 only. Purslane was the only weed species in which counts were higher in th e cultivated plots than in the untreated check du ring the second year. Cultivation controlled the weeds that were present well (in many cases as well as herbicides), however it did not pr event the re-establishment of ma ny of these weeds. Overall, cultivation resulted in similar weed control at both locations with the exception of a few weed species. Most notably, cultivation had the opposite effect on purple nutsedge during the fallowing period compared to Live Oak. Effect of Fallow Herbicides on Weeds (R egardless of Cultivation) Live Oak In general herbicide treatm ents provided bett er weed control than non-herbicide treated plots. In addition, there us ually was no difference between weed counts in glyphosate and glyphosate plus halosulfuron treated plots. Glyphosate and glyphosate plus halosulfuron treatments provided better weed control than non-herbicide treatments for several weeds including, pusley and hairy in digo. Glyphosate treatments contro lled smallflower morningglory better than non-herbicide treatments. There were no differences in weed control efficacy between glyphosate and glyphosate mixed with halosulfuron for any weeds. Fallow Herbicide Effects on Weeds In general, herbicides provided better weed control than the untreated check and in many cases outperfor med cultivation. This was the tr end observed for purple nutsedge and Florida pusley in Live Oak. However, yellow nutsedge and carpetweed did not follow this pattern. Yellow nutsedge levels in herbicid e plots were comparable to the levels in the cultivated check plot, but lower than the levels in the untreated check. Directly after cultivati ng the glyphosate plus cultivation plot there was a significant increase in carpetweed compared to the uncultivated glyphosate plot in Live Oak.

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271 Herbicides provided better weed control than the untreated check for most weed species following an herbicide applica tion. Glyphosate provided excelle nt systemic post-emergent control of most weed species at both locations Increased weed control was achieved with glyphosate when applied to actively growing plants in moist soils compared to drought stressed plants in dry soils. In addition, paraquat a pplications resulted in temporary burndown post emergent control of most weed species in Citr a. Besides burndown cont rol, paraquat provided complete weed control of many species when mu ltiple applications were made in conjunction with tillage. All herbicides and herbicide comb inations provided better yellow nutsedge control than paraquat during the second year of fallowi ng in Citra. Neither glyphosate nor paraquat provided pre emergent control or residual cont rol of weeds. Adding trifloxysulfuron or smetolachlor to glyphosate or paraquat often impr oved post-emergent control and provided pre emergent control of weeds. Sulfonylurea herbicides did not perform simila rly at both locations. There usually was not any difference in weed counts between glyphosate and glyphosate plus halosu lfuron in Live Oak. At Live Oak, glyphosate provide d excellent weed control by itself and the addition of halosulfuron did not provide any incremental control. Ideal weat her conditions may have lead to the high level of control provide d by glyphosate. Under suboptim al conditions halosulfuron may have improved weed control. Adding trifloxysulfuron to glyphosate or paraquat improved postemergent control of purple nutsedge and pre-emergent control of most broadleaf weeds in Citra. This pattern was observed for amaranth, pursl ane, Florida pusley, cutleaf ground cherry and carpetweed. There were increased purple nutsedge counts in the glyphosate tank-mixed with smetolachlor treated plots compared to the gl yphosate plus trifloxysulfuron plots during the

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272 second year. No differences in purple nutsedge control between glyphos ate and paraquat were observed either year. An increase in weed control was observed for yellow nutsedge and crabgrass and other grass species when addi ng s-metolachlor to glyphosate or paraquat. At the Live Oak location, cult ivation practice typi cally did not affect weed counts in herbicide treated areas. All he rbicides and herbicide combina tions performed equally for the following weeds: crabgrass and Florida pusley during the first year and yellow nutsedge during the second year (counts) in Citra. Many times all herbicide combinati ons killed the weeds present at the time of applic ation but did not provide any residual control, except for trifloxysulfuron. All post-emergent herbicides pe rformed better when applied to small, tender, succulent, more susceptible weeds. All herb icides performed better under conditions that stimulated weed growth, such as warm te mperatures and optimal soil moistures. Effect of Fallow Treatments on Weeds within Peppers Untreated Fallow Effect on Peppers Live Oak The untreated check resulted in lower purple nu tsedge counts than the cultivated check, but not lower than the herbicide treatm ents during year one. During year two, the untreated check had the highest amount of purple nutsedge within the pepper row compared to all the other fallow treatments. Fallow Cultivation Effect on Peppers Live Oak Fallow cultivation plots containe d the greatest amount of purp le nutsedge during the first pepper c rop. Cultivation during the fallow period resulted lower purple nutsedge counts than the untreated control, but higher nut sedge counts than the herbicide treated plots during the second pepper crop.

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273 Effect of Fallow Herbicides on Bell Pepper (Regardless of Cultivation ) Live Oak Glyphosate and glyphosate tank-mixed with halo sulfuron increased Florida pusley control within both pepper rows and row middles. In addition, crabgrass row middle control was increased by glyphosate and glyphosate plus halo sulfuron. Peppers were taller in the nonherbicide plots compared to both herbicide treatments. Fallow Herbicide Effect on Peppers Live Oak Herbicide treatm ents did not lower purple nuts edge counts more than the untreated check, but did lower purple nutsedge counts more than the cultivated check. In the second pepper crop, herbicides reduced purple nutsedge numbers more th an the cultivated and untreated check plots. There was no difference in purple nutsedge control between glyphosate and glyphosate tankmixed with halosulfuron, w ith or without cultivation. Effects of Fallow Treatments on Snap Beans Effect of Fallow Cultivation in Snap Bean s (Regardless of Herbicides) Live Oak Fallow cultivation p rior to planting decrease d the crabgrass presence during the first cropping season in snap beans. Effect of Fallow Herbicides on Snap Be ans (Regardless of Tillage) Live Oak Percent weed cover of all weed species co m bined, Florida pusley, and crabgrass numbers were decreased by glyphosate and glyphosate plus halosulfuron during th e first year. Glyphosate tank-mixed with halosulfuron controlled smallf lower morningglory bette r than non-herbicide treatments in bean rows during the second y ear. Purple nutsedge was controlled better by glyphosate and glyphosate tank mixed with halosulf uron compared to non-herbicide plots both years of the study. There were no differenc es in weed control between glyphosate and glyphosate plus halosulfuron treatm ents for any of these weeds.

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274 Effect of Fallow Treatments on Weeds w ithin Cabbage Untreated Fallow Effect on Cabbage The untrea ted check resulted in the lowest le vel of purple nutsedge compared to all the other treatments in cabbage during the sec ond cropping season. There were no significant differences in cabbage yields between fallow trea tments in Live Oak. The weed species that were present during the summer fallow were kill ed by frost or in a dormant stage during the winter cabbage crop in Live Oa k. The only weeds that were pr esent were winter annuals. Therefore there was not much weed competition fr om weeds controlled by fallow treatments. The Citra location was much warmer during the winter compared to the Live Oak location. Thus summer annuals were not killed by the fros t and perennials did not go dormant. There was more competition from summer weed population in Citra compared to Live Oak due to the warmer weather. The untreated control typically resulted in the lowest weed control, the highest weed counts, the lowest cabbage vigor and yields. Purslane infe station was less in the untreated plots compared to the other treatments. The unt reated control provided si milar weed control and cabbage yields as many of the other treatments in Citra. Fallow Cultivation Effect on Cabbage Cultiva tion during the fallow period resulted in a higher level of purple nutsedge control than the untreated check, but provided less contro l than the herbicide treatments in Live Oak. Tillage killed purple nutsedge shoots and deplet ed tuber carbohydrate reserves over a long period of time. Biweekly hand hoeing during the cropping season resulted in higher weed control than the untreated check, but did not improve cabbage vigor or yield in Citr a. In addition, hand hoeing provided weed control co mparable to the best herbicid e treatments for purple nutsedge and crabgrass. Yellow nutsedge control was high er in the cultivated check compared to the untreated check, but was lower than the control provided by herbicides in Citra. However,

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275 yellow nutsedge was non existent in most plots after the second hand hoeing, therefore data was not collected. Purslane control was similar between the best herbicide treatments, the cultivated check, and the untreated check. Fallow Herbicide Effect on Cabbage Live Oak Treatm ents that contained herbicides, glyphosate and glyphosate tank-mixed with halosulfuron, provided the highest level of purple nutsedge contro l. There was no difference in purple nutsedge contro l between glyphosate and glyphosate ta nk-mixed with halosulfuron, with or without cultivation. Fallow Herbicide Treatment Effect on Weeds during Cabbage Crop Citra Weed control was highest in th e herbicide treated plots. Herbicides applied during the fallow often provided the sam e level of weed control as hand hoeing every other week (cultivated check) during the crop. This was observed in all weeds on all sample dates except for purple nutsedge, yellow nutsedge and pursl ane on the first sample date. Many times the different fallow herbicides re sulted in similar weed control during the cropping season for crabgrass and purslane. Sometim es the fallow herbicide treatments provided variable control depending on the weed spec ies for purple and yellow nutsedge. At the beginning of the crop paraquat plus s-metolachlo r controlled purple nu tsedge better than glyphosate alone. S-metolachlor mixed with either glyphosate or paraquat provided better yellow nutsedge control than glyphosate by itself. Fallow Treatment Effect on Cabbage Vigor and Yield Citra Overall, the untreated check and the cultivated check consistently resulted in the poorest cabbage stand establishment, size, vigor, and yield. In addition, it appears trifloxysulfuron negatively affected cabbage si ze, vigor, and yield.

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276 The untreated check, the cultivated check a nd the plots treated with glyphosate plus trifloxysulfuron had the lowest ca bbage vigor and yields. All th e other fallow herbicide plots resulted in the highest cabbage vigor. Trifl oxysulfuron tank-mixed with either glyphosate or paraquat, the untreated check, and the cultivated check yielded the smallest cabbage size per head. The untreated check, the cultivated check and the plots treated with glyphosate tank-mixed with s-metolachlor during the fallow period had th e lowest stand establishment. All the other fallow herbicide, except those herbicide treat ments with trifloxysulfuron, had higher cabbage yield and size. Effect of Pre-plant Herbicides on Cabbage In regards to pre-plant herbic ides, oxyfluorfen provided the be st weed control and highest yields com pared to s-metolachlo r and the untreated subplots for mo st weed species in Live Oak. Furthermore, s-metolachlor did not control w eeds as well as oxyfluor fen but provided better control than the untreated subplots in general. In Citra, s-metol achlor provided greater control of purple and yellow nutsedges, but not to the extent as fallow herbicide treatments. Oxyfluorfen provided superior control of gra sses and broadleaf weeds. In addition, oxyfluorfen resulted in greater cabbage size and total yield when compar ed to s-metolachlor in Citra. Crabgrass was controlled better by oxyfluorfen compared to s-meto lachlor. Oxyfluorfen provided a higher level of cutleaf evening primrose and purslane compared to s-metolachlor. Based upon the results of these studies, it is recommended to apply herbicides during the fallow period to control weeds. A sulfonylurea he rbicide used in conjunction with glyphosate or paraquat to provide pre, post c ontrol and residual of broadl eaves and sedges for non-sensitive crops. Sulfonylurea herbicides should not be used in sensitive crops such as cabbage. Adding smetolachlor to glyphosate or paraquat will provide pre-plant control, not provided by glyphosate or paraquat alone. Both glyphosate and para quat are recommended for weed control because

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277 they are inexpensive, provide good weed control, and do not nega tively impact crop yields. It would be beneficial to implement herbicide fallow weed control to control perennial weeds such as purple and yellow nutsedge. Fallow weed contro l is very beneficial to control all weeds in minor vegetable crops that have no registered herbicides labeled for use in those crops. Herbicide fallow and cultivation decrease a nnual weed presence by lim iting the seed rain deposited into the soil seed bank. Furthermore, cultivation depletes the soil seed bank by seed burial and seedling emergence. Cultivation woul d be useful for contro lling annual weeds in organic production systems. Cultivation also controls nutsedges but not nearly as well as herbicide treatments, but is an option for those systems excluding herbicides from the weed management program. Based upon the results from this study, applying a pre-plant herbicide in addition to implementing fallow weed control measures is recommended to control annual weeds. Oxyfluorfen provides th e best control of emerging grasses and broadleaves seedlings missed by fallow weed control.

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278 LIST OF REFERENCES Aguyoh, J. N. and J. B. Masiunas. 2 003. Interference of large crabgrass ( Digitaria sanquinalis ) with snap beans. W eed Sci. 51:171-176. Aguyoh J. N. and Masiunas. 2003. Interference of redroot pigweed ( Amaranthus retroflexus) with snap beans. Weed Sci. 51:202-207. Anderson, W. P. 1996. Weed science: principl es and applications. 3rd ed. West Publishing Co., St. Paul, MN. Baker, H. G. 1974. The evolution of weeds. Annu. Rev. Ecol. Syst. 5:1-24. Bariuan, J. V., K. N. Reddy, and G. D. Wills. 1999. Glyphosate injury, rainfastness, absorption, and transloca tion in purple nutsedge ( Cyperus rotundus ). Weed Technol. 13:112119. BASF Corporation Agricultura l Products labels, Res earch Triangle Park, NC. Bibhas, R. and M. Wilcox. 1969. Chemical fall ow control of nutsedge. Weed Res. 9:86-94. Booth, B. D., S. D. Murphy, and C. J. Swanton. 2003. Weed ecology in natural and agricultural systems. CABI Publishing, Cambridge, MA. Brandenberger, L. P., J. W. Shrefler, C. L. Webber III, R. E. Talbert, M. E. Payton, L. K. Wells, and M. McClelland. 2005. Pre emergence weed control in direct-seed ed watermelon. Weed Technol. 19:706-712. Brandenberger, L. P., R. E. Talbert, R. P. Wied enfeld, J. W. Shrefler, C. L. Webber III, and M. S. Malik. 2005. Effects of halosulfuron on weed control in commercial honeydew crops. Weed Technol. 19:346-350. Brecke, B. J., D. O. Stephenson IV, and J. B. Unruh. 2005. Control of Purple Nutsedge ( Cyperus rotundus ) with Herbicides and Mowing. Buker R. S., III, S. M. Olson, W. M. Stall, and D. G. Shilling. 1998. Watermelon yield as affected by competition from varying yellow nutsedge ( Cyperus escultentus ) populations. Proc. South. Weed Sci. Soc. 51:95-96. Caldwell, B. and C. L. Mohler. 2001. Stale Seedbed Practices for Vegetable Production. HortScience. 36(4):703-705. Chachalis, D., K. N. Reddy, C. D. Elmore, and M. L. Steele. 2001. Herbicide efficacy, leaf structure, and spray droplet contact a ngle among Ipomoea species and smallflower morningglory. Weed Sci. 49:628-634.

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279 Cools, W. G., and S. J. Locascio. 1977. Control of purple nutsedge ( Cyperus rotundus L.) as influenced by season of application of glyphosate a nd nitrogen rate. Proc. South. Weed Sci. Soc. 30:158-164. Deepak, M. S., T. H. Spreen, and J. J. VanSickle. 1996. An analysis of the impact of a ban of methyl bromide on the U.S. winter fresh vegeta ble market. Jornal of Agr. And Appl. Econ. 28(2):433-443. Dow AgroSciences LLC labels, Indianapolis, IN. Dusky, J. A., C. W. Deren, and D. B. Jone s. 1997. Competition between yellow nutsedge ( Cyperus esculentus) and rice (Oryza sativa ). Proc. South. Weed Sci. Soc. 50:152. Earl, H. J., J.A. Ferrell, W. K. Vencill, M. W. van Iersel, and M. A. Czarnota. 2004. Effects of three herbicides on whole-plant carbon fi xation and water use by yellow nutsedge ( Cyperus esculentus). Weed Sci. 52:213-216. Edenfield, M. W. 2000. Purple nutsedge ( Cyperus rotundus ) dynamics in glyphosate-tolerant crops. Univ. of Fl., Gainesville, PhD Diss. FMC Corporation Agricultural Produc ts Group labels, Philadelphia, PA. Glaze, N. G. 1987. Cultural and mechanical manipulation of Cyperus Spp Weed Technol. 1:32-83. Gown Company labels, Yuma, AZ. Holm, L. G., D. L. Plucknett, J. V. Pancho, J. P. Herberger. 1977. The Worlds Worst Weeds: Distribution and Biology. The Univers ity Press of Hawaii, Honolulu, Hawaii. Hauser, E. W., J. L. Butler, J. L. Shepherd, and S.A. Parham. 1966. Response of yellow nutsedge, Florida pusley, and peanuts to thiocar bamate herbicides as affected by method of placement in soil. Weed Res. 6:338-345. Hunt, R. 1988. Analysis of growth and resource allocation. Weed Res. 28:459-463. Johnson III, W. C. and B. G. Mullinix, Jr. 1998. Stale seedbed weed control in cucumber. Weed Sci. 46:698-702. Johnson, W. C. and B. G. Mullinix. 1999. Cyperus esculentus interference in Cucumis sativus Weed Sci. 47:327-331. Johnson III, W. C. and B. G. Mullinix Jr. 2005. Effect of application method on weed management and crop injury in transplanted cantaloupe production. Weed Technol. 19:108112. Kadir, J. B., R. Charudattan, W. M. Sta ll, and T. A. Bewick. 1999. Effect of Dactylaria higginsii on interference of C yperus rotundus with L. esculenum Weed Sci. 47:682-686.

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280 Keeley, P. and R. Thullen. 1975. Influence of yellow nutsedge competition on furrow-irrigated cotton. Weed Sci. 23:171-175. Knezivic, S. Z., M. J. Horak, and R. L. Va nderlip. 1997. Relative time of redroot pigweed ( Amaranthus retroflexus L.) emergence is critical in redroot pigweed-sorghum [Sorghum bicolor (L. ) Moench] competition. Weed Sci. 45:502-508. Lonsbary, S. K., J. OSullivan, and C. J. Swanton. 2003. Stale-seedbed as a weed management alternative for machine-harvested cucumbers ( Cucumis sativus ). Weed Technol. 17:724-730. Marini, R. P. 2003. Approaches to analyzing experiments with factor ial arrangements of treatments plus other treatments. Hort. Sci. 38(1):117-120. Masin R., M. C. Zuin, S. Otto, G. Zanin. 2006. Seed longevity and dormancy of four summer annual grass weeds in turf Weed Res. 46:362-370. McAvoy, E. J. and W. M. Stall. 2008. Toma to, pepper, and watermelon tolerance to EPTC applied under mulch in Florida. Southern Weed Science Society Proceedings p.141. McNaughton, K. E., P. H. Sikkema, and D. E. Robinson. 2004. Snap bean tolerance to herbicides in Ontario. Weed Technol. 18:962-967. Monks, D. W. and J. R. Schultheis. 1998. Critical weed-free peri od for large crabgrass ( Digitaria sanguinalis ) in transplanted watermelon ( Citrullus lanatus ). Weed Sci. 46:530-532. Morales-Payan, J. P., and W. M. Stal l. 1997. Effect of purple nutsedge ( Cyperus rotundus ) population densities on th e yield of eggplant ( Solanum melongena). HortSci. 32(3):431. Morales-Payan, J. P., B. M. Santos, W.M. Stall, and T. A. Bewick. 1997a. Effects of purple nutsedge (Cyperus rotundus) on tomato (Lycopersicon esculentum) and bell pepper (Capsicum annum) vegetative growth and fru it yield. Weed Technol. 11:672-676. Morales-Payan, J. P., B. M. Santos, and W. M. Stall. 1997b. Weed management in solanaceous crops in the Dominican Republic. Pr oc. Caribb. Food Crops Soc. 33:333-339. Morales-Payan, J. P., W. M. Stall, D. G. Sh illing, R. Charuadattan, J. A. Dusky, and T. A. Bewick. 2003. Aboveand belowground interf erence of purple and yellow nutsedge ( Cyperus spp.) with tomato. Weed Sci. 51:181-185. Mossler, M., M. J. Aerts, and O. N. Nesheim. 2006. Florida crop/pest management profiles: bell peppers. University of Florida/IFAS Extension. Electro nic Information Data Source. http://edis.ifas.ufl.edu/PI040 Mulahey, J. J., J. P. Gilreath, W. M. Stall, J. A. Dusky, J. G. Norcini, M. Singh, and J. Weinbrecht. 1999. Proceedings, Southern Weed Science Society, 52:281. Neeser, C., R. Aguero, and C. J. Swanton. 1997. Survival and dormancy of purple nutsedge ( Cyperus rotundus ) tubers. Weed Sci. 45:784-790.

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281 Nelson, K. A. and K. A. Renner. 2002. Yellow Nutsedge ( Cyperus esculentus ) Control and Tuber Production with Glyphosate and ALS-Inhib iting Herbicides. Weed Technol. 16:512-519. Nelson, K. A., K. A. Renner, and D. Penner. 2002. Yellow nutsedge ( Cyperus esculentus) control and tuber yield with glyphosate a nd glufosinate. Weed Technol. 16:360-365. Radosevich, S., J. Holt, and C. Ghersa. 1997. Weed ecology: implecations for management. 2nd ed. John Wiley and Sons, Inc., New York, NY Santos, B.M., J. A. Dusky, W. M. Stall, D. G. Shilling, and T. A. Bewick. 1997. Influence of smooth pigweed and common purslane densities on lettuce yields as a ffected by phosphorous fertility. Proc. Fla. State Hortic. Soc. 110:315-317. Santos, B. M., J. A. Dusky, T. A. Bewick, and D. G. Shilling. 2004. Mechanisms of interference of smooth pigweed (Amaranthus hybridus ) and common purslane ( Portulaca oleracea ) on lettuce as influenced by phosphor us fertility. Weed Sci. 52:78-82. Santos, B. M. 2009. Drip-applied metam pot assium and herbicides as methyl bromide alternatives for Cyperus control in tomato. Crop Protection. 28:68-71. Schneider, S. M., E. N. Rosskopf, J. G. Leesc h, D. 0. Chellemi, C. T. Bull, and M. Mazzola. 2003. United States Department of Agriculture-A gricultural Research Service research on alternatives to methyl bromide: pre-plan t and post-harvest. Pest Manag. Sci. 59:814-826. Senseman, S. A. 2007. Herbicide handbook. 9th ed. Weed Science Society of America, Lawrence, KS. Sharma, S.D. and M. Singh. 2007. Effect of ti ming and rates of application of glyphosate and carfentrazone herbicides and their mixtures on th e control of some broadleaf weeds. HortSci. 42(5):1221-1226. Smith, E. V. 1942. Nutgrass eradication studies III. The control of nutgrass, Cyperus rotundus L, on several soil types by tilla ge. Agronomy Journal 34: 151-159. Smith, E. V. and E. L. Mayton. 1938. Nutgrass eradication studies II. The eradication of nutgrass, Cyperus rotundus L., by certain tillage treatmen ts. Agronomy Journal 30:18-21. Siriwardana, G. and R. K. Nishimoto. 1987. Propagules of purple nutsedge ( Cyperus rotundus) in soil. Weed technol. 1:217-220. Stall, W. M. and J. P. Gilreath. 2005. Estim ated effectiveness of recommended herbicides on selected common weeds in Florida vegetables. Vegetable Production Handbook of Florida. Stall, W. M. 1999. Integrating non-chemical me thods to enhance weed management. Abstract FACTS Vegetable and Methyl Bromide Proc. Stevens, O. A. 1932. The number and weight of seeds produced by weeds. Am. J. Bot. 19:784794.

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282 Syngenta Crop Protection labels, Greensboro, NC. VanSickle, J. J., C. Brewster, T. H. Spreen. 2000 Impact of a methyl bromide ban on the U.S. vegetable industry. University of Florida/IFAS Extension-Bulletin 333. Webster, T. M and G. E. MacDonald. 2001. A Surv ey of Weeds in Various Crops in Georgia. Weed Technol. 15:771-790. Webster, T. M. 2003. Nutsedge (Cyperus spp.) eradiation: impossible dream? http://www. Fcnanet.org/proceedings/2002/Webster.pdf Webster, T. M., J. Cardina, and A. D. White 2003. Weed seed rain, soil seedbanks, and seedling recruitment in no-tillage cr op rotations. Weed Sci. 51:569-575. William, R. D. and G. F. Warre n. 1975. Competition between purple nutsedge and vegetables. Weed Sci. 23:317-323. The Columbia Encyclopedia, Sixth Edition Co pyright 2004, Columbia University Press. Licensed from Lernout & Hauspie Speech Products N.V.

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BIOGRAPHICAL SKETCH Theodore (T eddy) Porter McAvoy was born in New Brunswick, New Jersey on in 1982. He was born to Eugene Joseph McAvoy and D onna Marie McAvoy. Teddy is the middle child of three sons. His mother and father worked in overseas development organizations such as Peace Corps and USAID. This allowed him to trav el to Jamaica from the age of 2 years old until 6 years of age. Here he was received basic schooling in a one room school house managed by Mrs. Hall. After living in Jamaica the family moved to Pine Island, FL. Teddy lived in Pine Island, FL and Cape Coral, FL from second grad e until sixth grade. He attended elementary school at Pine Island Elementary, Franklin Pa rk Elementary, and Lee Middle School. Both Franklin Park and Lee Middle were science a nd technology magnet schools. Again the family moved, this time to Swaziland in southern Africa. In Swaziland, Teddy attended a private secondary school named Waterford Kamhlaba. Intere stingly the children of former President of South Africa, Nelson Mandela attended this school during the apartheid era. The family returned to Pine Island, Fl. Teddy attended high school at Mariner High School in Cape Coral, Florida, There he excelled in both academics and wrest ling. After graduating high school in 2000, Teddy was accepted to the University of Florida. Teddy ha s been at the University of Florida, since the fall of 2000. Interestingly his time spent at the university has been the longest he has ever lived in the same city. Teddy graduated and received his bachelor of science degree in horticultural sciences in the department in the fall of 2005. Teddy started hi s Masters program in the spring of 2006 in the Horticultural Sciences Department with an emphasis in Weed Science under the direction of advisor Dr. William Stall. His mast ers project focused on fallow weed control in Florida vegetable crops. He recei ved his M.S. from the University of Florida in the spring of 2009.