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Investigating Ipm Tactics to Reduce Pests and Disease Incidence and Increase Marketable Yields in Organic Squash Production

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Title:
Investigating Ipm Tactics to Reduce Pests and Disease Incidence and Increase Marketable Yields in Organic Squash Production
Creator:
Razze, Janine M
Place of Publication:
[Gainesville, Fla.]
Florida
Publisher:
University of Florida
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Language:
english
Physical Description:
1 online resource (157 p.)

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Entomology and Nematology
Committee Chair:
LIBURD,OSCAR EMANUEL
Committee Co-Chair:
WEBB,SUSAN E
Committee Members:
MCSORLEY,ROBERT T
NUESSLY,GREGG STEPHEN
TREADWELL,DANIELLE D
Graduation Date:
8/9/2014

Subjects

Subjects / Keywords:
Buckwheat ( jstor )
Crops ( jstor )
Immatures ( jstor )
Insecticides ( jstor )
Intercropping ( jstor )
Live mulches ( jstor )
Natural enemies ( jstor )
Pests ( jstor )
Population decline ( jstor )
Squashes ( jstor )
Entomology and Nematology -- Dissertations, Academic -- UF
aphids -- biocontrol -- buckwheat -- insecticides -- ipm -- organic -- squash -- whitefly
City of Gainesville ( local )
Genre:
bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Entomology and Nematology thesis, Ph.D.

Notes

Abstract:
Zucchini squash, Cucurbita pepo L., is a high value vegetable crop in Florida. Aphids and the silverleaf whitefly are considered significant pests of squash and are responsible for transmitting plant viruses. Information on organic pest management is limited and sometimes unavailable for many growers. In this study several integrated pest management (IPM) strategies were evaluated to reduce pests and disease incidence while increasing marketable yield in organic squash production. Objective 1 investigated how the presence of buckwheat and a key natural enemy, Delphastus catalinae, affected whitefly colonization on squash. Whitefly densities were greater on squash when compared with buckwheat. Delphastus catalinae released in exclusion cages in the greenhouse significantly reduced whitefly populations on squash. Objectives 2 and 3 compared planting arrangements of intercropped buckwheat and squash augmented with D. catalinae, to evaluate effects on pests, disease incidence, natural enemies, and marketable yields in field-grown squash. The treatments included buckwheat alternating (A) on either side of the squash with and without D. catalinae, buckwheat in the middle (B) of squash planted on either side with and without D. catalinae, buckwheat on both sides of squash (C), a bareground treatment, and a mixed varieties treatment. The field experiments demonstrated that aphid densities and insect-transmitted viruses were reduced, while natural enemies were more abundant, in buckwheat treatments compared with bareground treatments. However, the effect of buckwheat on whitefly populations was variable. Ultimately, marketable yields were not significantly different between the bareground treatment and buckwheat arrangements A and B. Furthermore, there were no differences among treatments with similar intercropping tactics when considering the effect of D. catalinae on pest populations, and significant dispersal between plots was observed. Objective 4 evaluated the effect of insecticides approved for organic use on silverleaf whitefly and D. catalinae in squash. Insecticide treatments included PyGanic, M-Pede, AzaSol, Entrust, and an untreated control. Adult and immature whitefly populations were reduced when applying PyGanic with a delayed release of D. catalinae 3-5 d after spraying. The findings from this study will be useful for incorporating several management strategies for the suppression of aphid and whitefly pests in organic squash productions. ( en )
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.
Thesis:
Thesis (Ph.D.)--University of Florida, 2014.
Local:
Adviser: LIBURD,OSCAR EMANUEL.
Local:
Co-adviser: WEBB,SUSAN E.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2015-08-31
Statement of Responsibility:
by Janine M Razze.

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Embargo Date:
8/31/2015
Classification:
LD1780 2014 ( lcc )

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INVESTIGATING IPM TACTICS TO REDUCE PEST S AND DISEASE INCIDENCE AND INCREASE MARKETABLE YIELDS IN ORGANIC SQUASH PRODUCTION By JANINE RAZZE A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN P ARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2014

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© 2014 Janine Razze

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To my Mom and Dad, who taught me the importance of dedication, passion, and ser vice to the community; and to Tim, whose love, support, and laughter helped tremendously along this journey.

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4 ACKNOWLEDGMENTS I would like to thank my major professor, Dr. Oscar E. Liburd, for his support and guidance throughout this study. I would also like to thank Drs . Robert McSorley, Gregg Nuessl y, Danielle Treadwell, and Susan Webb for serving on my supervisory committee and for their guidance and input into this study. I would like to also thank Drs. Tesfa Mengi stu, Nick Sekora, and Susan Webb for their expertise and guidance in using PCR and ELISA techniques for virus detection. I thank the staff and graduate students of the Small Fru it and Vegetable IPM Laboratory at the University of Florida for their help in data collection , as well as for cont ributing to an encouraging and stimulating environment to work in . I also would like to thank the staff and workers at the Plant Science, Research and Education Unit, University of Florida, and in particular Buck Nelson for his constant support and help in growing and maintaining the squash plants for my research. I would like to thank Charley Andrews from Hammock Hollow Farms for helping me grow and maintain my squash plots and giving me the opportunity to work with him on his farm. Special thanks go to my family and friends for their love and support.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ................... 12 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 14 Justification ................................ ................................ ................................ ............. 18 Statement of Problem ................................ ................................ ............................. 19 2 LITERATURE REVIEW ................................ ................................ .......................... 21 Pest Biology and Damage ................................ ................................ ...................... 21 Aphids ................................ ................................ ................................ .............. 21 Whiteflies ................................ ................................ ................................ .......... 23 Using Insecticides to Manage Insect Pest Populations in Organic Squash ............ 25 Integrated Pest Management Strategies ................................ ................................ . 28 Biological Control ................................ ................................ ............................. 28 Synthetic Mulche s ................................ ................................ ............................ 30 Habitat Manipulation and Living Mulches ................................ ......................... 31 3 PREFERENCE OF THE SILVERLEAF WHITEFLY ON ZUCCHINI SQUASH AND BUCKWHEAT AND THE EFFECT OF DELPHASTUS CATALINAE ............. 36 Materials and Methods ................................ ................................ ............................ 38 Results ................................ ................................ ................................ .................... 40 Discussion ................................ ................................ ................................ .............. 43 4 INVESTIGATING VARIOUS TACTICS OF INTERCROPPING BUCKWHEAT WITH SQUASH TO REDUCE PEST S AND DISEASE INCIDENCE AND INCREASE YIELD ................................ ................................ ................................ .. 54 Materials and Methods ................................ ................................ ............................ 57 Plot Preparation and Experimental Design ................................ ....................... 57 Sampling ................................ ................................ ................................ .......... 61 Data Analysis ................................ ................................ ................................ ... 64 Results ................................ ................................ ................................ .................... 65 Aphids ................................ ................................ ................................ .............. 65 Whiteflies ................................ ................................ ................................ .......... 66

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6 Diseases ................................ ................................ ................................ ........... 68 Natural Enemies ................................ ................................ ............................... 70 Plan t Measurements and Marketable Yields ................................ .................... 73 Discussion ................................ ................................ ................................ .............. 76 Aphids ................................ ................................ ................................ .............. 76 Whiteflies ................................ ................................ ................................ .......... 77 Diseases ................................ ................................ ................................ ........... 78 Natural Enemies ................................ ................................ ............................... 79 Plant Measurements and Marketable Yields ................................ .................... 81 5 EVALUATION OF ORGANICALLY APPROVED INSECTICIDES FOR CONTROL OF SILVERLEAF WHITEFLY IN ORGANIC SQUASH ...................... 118 Materials and Methods ................................ ................................ .......................... 120 Results ................................ ................................ ................................ .................. 123 Effectiveness of Organically Approved Insecticides on Whiteflies in Organic Squash ................................ ................................ ................................ ........ 123 Effects of Selected Insecticides on Delphastus catalinae ............................... 124 Discussion ................................ ................................ ................................ ............ 127 Effectiveness of Organically Approved Insecticides on Whiteflies in Organic Squash ................................ ................................ ................................ ........ 127 Effects of Selected Insecticides on Delphastus catalinae ............................... 128 6 CONCLUSION ................................ ................................ ................................ ...... 142 LIST OF REFERENCES ................................ ................................ ............................. 148 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 157

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7 LIST OF TABLES Table page 4 1 Mean ± SEM of natural enemies sampled by in situ counts for the intercro pping field study in fall 2011 . ................................ ................................ .. 85 4 2 Mean ± SEM of natural enemies sampled by in situ counts for the intercropping field study in fall 2012. ................................ ................................ .. 86 4 3 Mean ± SEM of natural enemies collected from yellow stick traps for the intercropping field study in fall 2011. ................................ ................................ .. 87 4 4 Mean ± SEM of natural enemies collected from yellow sticky traps for the intercropping field study in fall 2012 ................................ ................................ ... 88 4 5 Mean ± SEM of natural enemies collected from pitfall traps for the intercropping field study in fall 2012 ................................ ................................ ... 89

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8 LIST OF FIGURES Figure page 3 1 Mean ( ± SE) number of adult whiteflies observed for the whitefly preference study in spring 2011 ................................ ................................ ........................... 46 3 2 Mean ( ± SE) number of adult whiteflie s observed for the whitefly preference study in spring 2012 ................................ ................................ ........................... 47 3 3 Mean ( ± SE) number of 1 st instar immature whiteflies observed for the whitefly preference study in spring 2011 ................................ ................................ ......... 48 3 4 Mean ( ± SE) number of 1 st instar immature whiteflies observed for the whitefly preference study in spring 2012 ................................ ................................ ......... 49 3 5 Mean ( ± SE) number o f 2 nd 4 th instar immature whiteflies observed for the whitefly preference study in spring 2011 ................................ ............................ 50 3 6 Mean ( ± SE) number of 2 nd 4 th instar immature whiteflies observed for the whitefly pref erence study in spring 2012 ................................ ............................ 51 3 7 Mean ( ± SE) number of D. catalinae observed for the whitefly preference study in spring 2011 ................................ ................................ ........................... 52 3 8 Mean ( ± SE) number of D. catalinae observed for the whitefly preference study in spring 2012 ................................ ................................ ........................... 53 4 1 Diagrams of the different buckwheat arrangements implemented i n the intercropping field study ................................ ................................ ...................... 90 4 2 Mean ( ± SE) number of aphids sampled per squash leaf by in situ counts for the intercropping field study in fall 2011 ................................ ............................. 91 4 3 Mean ( ± SE) number of alate aphids sampled per pan trap for the intercropping field study in fall 2011 ................................ ................................ ... 92 4 4 Mean ( ± SE) number of aphids sampled per squash leaf by in situ counts for the intercropping field study in fall 2012. ................................ ............................ 93 4 5 Mean ( ± SE) number of alate aphids sampled per pan trap for the intercropping field study in fall 2012 ................................ ................................ ... 94 4 6 Mean ( ± SE) number of aphids sampled per squash leaf by in situ counts for the intercropping field study in fall 2013 ................................ ............................. 95 4 7 Mean ( ± SE) number of alate aphids s ampled per pan trap for the intercropping field study in fall 2013 ................................ ................................ ... 96

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9 4 8 Mean ( ± SE) number of immature whiteflies sampled from leaf discs for the intercropping field study in fall 2011 ................................ ................................ ... 97 4 9 Mean ( ± SE) number of adult whiteflies sampled from yellow sticky traps (YST) for the intercropping field study in fall 2011 ................................ .............. 98 4 10 Mean ( ± SE) number of immature whiteflies sampled from leaf discs for the intercropping field study in fall 2012 ................................ ................................ ... 99 4 11 Mean ( ± SE) number of adult whiteflies sampled from yellow sticky tr aps (YST) for the intercropping field study in fall 2012 ................................ ............ 100 4 12 Mean ( ± SE) number of immature whiteflies sampled from leaf discs for the intercropping field study in fall 2013 ................................ ................................ . 101 4 13 Mean ( ± SE) number of adult whiteflies sampled from yellow sticky traps (YST) for the intercropping field study in fall 2013 ................................ ............ 102 4 14 M ean ( ± SE) number of squash plants with virus symptoms for the intercropping field study in fall 2011 ................................ ................................ . 103 4 15 Mean ( ± SE) squash silverleaf (SSL) disorder symptom rating per squash plant for th e intercropping field study in fall 2011 ................................ .............. 104 4 16 Mean ( ± SE) number of squash plants with virus symptoms for the intercropping field study in fall 2012 ................................ ................................ . 105 4 17 Mean ( ± SE) squash silverleaf (SSL) disorder symptom rating per squash plant for the intercropping field study in fall 2012 ................................ .............. 106 4 18 Mean ( ± SE) number of squash plants with virus symptoms for the intercropping field study in fall 2013 ................................ ................................ . 107 4 19 Mean ( ± SE) squash silverleaf (SSL) disorder symptom rating per squash plant for the intercropping field stud y in fall 2013 ................................ .............. 108 4 20 Mean ( ± SE) height (cm) of squash plants sampled for the intercropping field study in fall 2011 ................................ ................................ ............................... 109 4 21 Mean ( ± SE) width (cm) of squash plants sampled for the intercropping field study in fall 2011 ................................ ................................ ............................... 110 4 22 Mean ( ± SE) height (cm) of squash plants sampled f or the intercropping field study in fall 2012 ................................ ................................ ............................... 111 4 23 Mean ( ± SE) width (cm) of squash plants sampled for the intercropping field study in fall 2012 ................................ ................................ ............................... 112

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10 4 24 Mean ( ± SE) height (cm) of squash plants sampled for the intercropping field study in fall 2013 ................................ ................................ ............................... 113 4 25 Mean ( ± SE) width (cm) of squash plants sampled for the intercropping field study in fall 2013. ................................ ................................ .............................. 114 4 26 Total marketable squash yield (kg) ( ± SE) harvested for the intercropping field study in fall 2011 ................................ ................................ ............................... 115 4 27 Total marketabl e squash yield (kg) ( ± SE) harvested for the intercropping field study in fall 2012 ................................ ................................ ............................... 116 4 28 Total marketable squash yield (kg) ( ± SE) harvested for the intercropping field study in fall 2013 ................................ ................................ ....................... 117 5 1 Mean ( ± SE) number of adult whiteflies observed per squash plant for the organically approved insecticide efficacy study in spring 2013 ......................... 132 5 2 Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved insecticide efficacy study in spring 2013 ......................... 133 5 3 Mean ( ± SE) number of adu lt whiteflies observed per squash plant for the organically approved insecticide efficacy study in spring 2014 ......................... 134 5 4 Mean ( ± SE) number of immature whiteflies observed per squash plant for th e organically approved insecticide efficacy study in spring 2014 ......................... 135 5 5 Mean ( ± SE) number of D. catalinae adults observed per squash plant for the organically approved insecticide efficacy st udy evaluating the release of D. catalinae in spring 2013 ................................ ................................ .................... 136 5 6 Mean ( ± SE) number of D. catalinae adults observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2014 ................................ ................................ .................... 137 5 7 Mean ( ± SE) number of adult whiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2013 ................................ ................................ .................... 138 5 8 Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2013 ................................ ................................ .................... 139 5 9 Mean ( ± SE) number of adult whiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2014 ................................ ................................ .................... 140

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11 5 10 Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved in secticide efficacy study evaluating the release of D. catalinae in spring 2014 ................................ ................................ .................... 141

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12 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of P hilosophy INVESTIGATING IPM TACTICS TO REDUCE PEST S AND DISEASE INCIDENCE AND INCREASE MARKETABLE YIELDS IN ORGANIC SQUASH PRODUCTION By Janine Razze August 2014 Chair: Oscar E. Liburd Major: Entomology and Nematology Z ucchini squash, Cucurbita pepo L ., is a high value vegetable crop in Florida . Aphids and the silverleaf whitefly are considered significant pests of squash and are responsible for transmitting plant viruses . Information on organic pest management is limited and sometimes unavailable for many growers . In this study several integrated pest management ( IPM ) strategies were evaluated to reduce pest s and disease incidence while increasing marketable yield in organic squash production. Objective 1 investigated how the presence of buckwheat an d a key natural enemy, Delphastus catalinae , affect ed whitefly colonization on squash . W hitefly densities were greater on squash when compared with buckwheat. Delphastus catalinae released in exclusion cages in the greenhouse significantly reduce d whitefl y populations on squash. Objective s 2 and 3 compare d planting arrangements of intercropped buckwheat and squash augmented with D. catalinae, to evaluate effects on pest s, disease incidence, natural enem ies , and marketable yields in field grown squash . The treatments include d buckwheat alternating (A) on either side of the squash with and without D. catalina e , buckwheat in the middle (B) of squash planted on either side with

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13 and without D. catalinae, buckwheat on both sides of squash (C) , a bareground treat me nt, and a mixed varieties treat ment. The field experiments demonstrated that aphid densities and insect transmitted virus es were reduced , while natural enemies were more abundant, in buckwheat treatments compared with bareg round treatments . However, t he effect of buckwheat on whitefly populations was variable . Ultimately, marketable yields were not significantly different between the bareground treatment and b uckwheat arrangements A and B. Furthermore, t here were no differences among treatments with simil ar intercropping tactics when considering the effect of D. catalinae on pest populations, and significant dispersal between plots was observed. Objective 4 evaluate d the effect of insecticides approved for organic use on silverleaf whitefly and D. catalina e in squash. I nsecticide treatments included PyGanic ® , M Pede ® , AzaSol ® , Entrust ® , and an untreated control. A dult and immature whitefly populations were reduced when applying PyGanic® with a delayed release of D. catalinae 3 5 d after spraying . Th e find ings from this study will be useful for incorporating several management strategies for the suppression of aphid and whitefly pes ts in organic squash production .

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14 CHAPTER 1 INTRODUCTION Cucurbits are a major vegetable crop grown in Florida and commercial product ion occurs throughout the year. Cucurbit crop production in the U S is broken down into 7 major classes: cucumber fresh, cucumber processing, cantaloupe, honeydew, pumpkin, squash, and water melon (Can tliffe et al. 2007). In 2012, Florida ranked firs t in the value of production of cucumber for fresh market, squash, and watermelon (FDACS 2013). In particular, zucchini squash, Cucurbita pepo L. (Cucurbitales: Cucurbitaceae) is a high value vegetable crop in Florida (Nyoike and Liburd 2010). For the 20 12 production season in Florida, squash was harvested from 9,700 acres (3,926 ha) and valued at approximately $67 million USD (FDACS 2013). Southeast Florida (Miami Dade County) is the principal squash producing region in Florida (Mossler and Nesheim 2001 ). Other important squash producing regions in the state include Lee, Hendry, and Collier counties in Southwest Florida; Hillsborough, Hardee, and Manatee counties in West Central Florida; and Alachua, Columbia, and Gilchrist counties in North Florida (Mo ssler and Nesheim 2001). Squash is a warm season plant that is adapted to cool conditions; therefore, squash is typically planted in Florida between 15 August and 1 Apr il (Mossler and Nesheim 2001). Squash grows best in a fertile, well drained soil, suc h as the deep, sandy soils common to Flori da (Mossler and Nesheim 2001). Squash is planted by direct seeding or transplanting seedlings, and is commonly grown on synthetic mulches in Florida (Mossler and Nesheim 2001). Although the majority of the squash produced

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15 in Florida is grown conventionally, about 20 25% is produced using USDA organic standards (Liburd 2012). Crop plant physiological disorders and insect transmitted viruse s are major problems for many growers around the state. Two key insect pests of zucchini squash in North Central Florida are aphids, including the melon aphid, Aphis gossypii Glover, and the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) , and the silverleaf whitefly, Bemisia tabaci (Gennadius) B biotype (Hemipte ra: Aleyrodidae) (Frank and Liburd 2005, Nyoike et al. 2008, Nyoike and Liburd 2010). These insect pests are largely responsible for transmitting viruses (i.e., Zucchini yellow mosaic virus transmitted by aphids, Squash vein yellowing virus and Cucurbit l eaf crumple virus transmitted by whiteflies) (Webb et al. 2003, Akad et al. 2008) and causing physiological disorders in squash (i.e., squash silverleaf disorder associated with the feeding of immature whiteflies) ( Yokomi et al. 1990 , Schuster et al. 1991 ) . Aphid and whitefly populations tend to be greater on squash planted in the fall than squash planted in the spring; therefore, the incidence of physiological disorders and insect transmitted viruses is typically greater in the fall ( Schuster et al. 1992 ). High infestations can cause stunting and eventual death of the plant, t hus reducing fruit production. Reduced fruit quality and failure to meet commercial grading standards can cause severe economic damage to growers (Mossler and Nesheim 2001). Mana gement of these pests is extremely difficult irrespective of the production system (conventional or organic) that growers are using. However, organic growers face an even more daunting task since a greater diversity of prophylactic pest controls are develo ped for conventional growers than organic growers, and often are not

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16 permitted in organic production (i.e., synthetic pesticides and fertilizers). Informa tion on organic pest management, particularly the efficacy of products and strategies available for or ganic production, is very limited and sometimes unavailable for many growers. Insecticides are an important management tactic for preventing pest population build up on the host, which can aid in reducing the proliferation of viruses and transmission among plants (Nyoike and Liburd 2010). However, attempts to manage aphids and whiteflies successfully throughout the season with the use of insecticides can be problematic because all life stages occur on the underside of leaves where they are not likely to be a ffected by contact pesticides. With regard to aphids, the application of contact and systemic insecticides to manage aphid populations provides insufficient control because aphids acquire and transmit viruses within 20 30 s, usually before the aphid vect or acquires a lethal insecticide dose (Gibson and Rice 1989). Furthermore, overdependence on insecticides has resulted in resistant populations to selected classes of insecticides (Manandhar et al. 2009). There is growing interest to increase knowledge and focus efforts on incorporating integrated pest management (IPM) strategies that are compatible with sustainable and organic production systems. Biological control is one management st rategy that is available to aid in pest suppression in organic squash p roduction systems due to the minimal use of broad spectrum and high residual insecticides in organic systems . Natural enemies are either naturally occurring in the environment or can be introduced into the production system through augmentation. Predators of aphids and whiteflies include ladybird beetles (Coleoptera: Coccinellidae), larvae of hoverflies (Diptera: Syrphidae), gall midge larvae (Diptera: Cecidomyiidae) and lacewing larvae (Neuroptera: Chrysopidae) (Schmidt et al.

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17 2003, McNeill et al. 2012). O ther biological control agents, including Encarsia formosa Gahan , Encarsia luteola Howard , and Eretmocerus californicus Howard (Hymenoptera: Aphelinidae) have been fairly successful in the greenhouse (Liburd and Nyoik e 2008). The coccinellid beetle Delpha stus catalinae (Horn) (Coleoptera: Coccinellidae), has been cited as a good biological control candidate for whiteflies as a result of high prey consumption rates, long adult lives, and high fecundity rates (Heinz et al. 1999), and is commercially availabl e for whitefly control (Simmons et al. 2008). Biological control is an effective management strategy, but is not a stand alone practice. Other tactics such as living mulches can be used in conjunction with biological control to support natural enemy popula tions. apparency to the pest (the resource concentration hypothesis; Root 1973). Furthermore, the increase in diversity of vegetation provided by living mulches se rves to attr act natural enemies and provides another level of pest management at a reduced cost (Hilje et al. 2001). Buckwheat, Fagopyrum esculentum Moench (Caryophyllales: Polygonaceae) has been cited as an important living mulch in cucurbit production systems (Hook s et al. 1998 , Frank and Liburd 2005 ). Significant reductions in aphid and whitefly densities, as well as the incidence of insect transmitted viruses , have been recorded when buckwheat was intercropped into squash production systems when compared with zucc hini in bare ground treatments (Hooks et al. 1998, Frank and Liburd 2005). Buckwheat is an annual plant that completes its life cycle in Florida in 6 w; however, it can be managed so that it produces seeds throughout the year and does not require

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18 subsequen t plantings later in the season (Frank and Liburd 2005). Buckwheat is of particular interest because it flowers profusely and attracts beneficial insects to the cucurbit crop (Platt et al. 1999, Frank and Liburd 2005). Furthermore, it can aid in the supp ression of weed species that can compete with the main crop for nutrients (Platt et al. 1999). Synthetic plastic mulches are used extensively in commercial vegetable production to improve crop growth and qu ality (McCraw and Motes 2007). In particular, ref lective mulches have also been used successfully to reduce pest incidence as well as the onset of diseases caused by aphid transmitted viruses and whitefly induced physiological disorders in squash (Summers and Stapleton 2002, Summers et al. 2004). However , there are considerable costs associated with the removal of plastic materials. Living mulches are considered a low cost alternative to synthetic mulches that, if adequately managed, provide high yields and net profits (Hilje et al. 2001). Justification Several studies have shown that aphid and whitefly populations are reduced in mixed cropping systems and in squash crops interplanted with nonhost cover crops or mulches (Hooks et al. 1998, Frank and Liburd 2005, Manandhar et al. 2009). These studies supp ort the idea that nonhost crops planted within the same field as the cash crop can serve as habitats for conserving and increasing populations of natural enemies; therefore, introducing diversity into agroecosystems for improved pest control (Platt et al. 1999). However, yields can be significantly reduced, most likely due to early season competition for shared resources (Nyoike and Liburd 2010). One potential way to reduce the costs and competitive effects of intercropping is to undersow in strips

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19 across t he field instead of planting over th e entire field (Gaolach 2002). Adjustments in plant spacing and time of planting may increase marketable yields, but more research is needed in this area. The implementation of cultural control techniques in agriculture , such as the augmentation and conservation of biological control and the implementation of living mulches, has the potential to reduce aphid and whitefly numbers as well as insect transmitted viruses on cucurbits. In an organic production system, further reduction of aphid and whitefly populations could be achieved by incorporating organically approved pesticides with other cultural control techniques. However, a lack of knowled ge on the effectiveness of products approved for organic p roduction is one of the constraints to organic squash production in Florida. Resear ch on the effectiveness of organically approved insecticides for managing pest populations in squash, as well as their effects on natural enemies will provide additional in formation for organic growers on how these insecticides can be used to regulate pest populations. Statement of Problem A more sustainable approach is needed to address the limitations of the current management strategy for key pests in organic squash produ ction. Current strategies in squash production rely on conventional insecticides to manage aphids and whiteflies and the dis eases they transmit in squash. More informati on on the effectiveness of organically approved insecticides and how they can be incor porated with other IPM techniques will provide additional tools for managing pest populations in organic squash as well as other emerging pests. The overall goal of this study was to evaluate several IPM strategies that may potentially reduce pest s and dise ase incidence while increasing

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20 marketable yiel d in organic squash production. The specific objectives were : 1) to conduct greenhouse trials to determine how the presence of buckwheat and a key natural enemy, Delphastus catalinae , affect whitefly colonizati on on zucchini squash; 2) to compare tactics of intercropping buckwheat and squash , while incorporating D. catalinae, to evaluate effects on pest and natural enemy densities, disease incidence, and marketable yields in field grown squash; 3) to use an on fa rm demonstration to implement the buckwheat incorporating D. catalinae, and compare to current organic squash growing practices; and 4) to evaluate the effect of organically approved insecticides on sil verleaf whitefly and D. catalinae in organically grown squash.

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21 CHAPTER 2 LITERATURE REVIEW Pest Biology and Damage Aphids Aphids (Hemipte ra: Aphididae) are small phloem sucking insects, and many species are considered significant pests for agricu lture. Aphid species vary greatly, from their host plant specialization to their abilities to transmit viruses. The melon aphid, Aphis gossypii Glover, and the green peach aphid, Myzus persicae (Sulzer) are particularly major pests of cucurbits, including watermelons, cucumbers, cantaloupes, and squash (Capinera 2001, Capinera 2009). Aphid females have the ability to be parthenogenetic, and can produce offspring without mating. This capability has contributed to their success as major agricultural pests. Aphids can complete development and rep roduce in as little as a week. Females are capable of producing a total of about 70 to 80 offspring within approximately 15 d at an optimum temperature of 25 ° C (Capinera 2009). Aphids cause plant damage by feeding on the sap in phloem vessels, such that the saliva injected during feeding may cause the leaves to become curled or cupped downwa rd (Mossler and Nesheim 2001). Heavy infestations may cause plants to gradually wilt, turn yellow or brown, and die ( Kessing and Mau 2007). Young plants may have reduced or stunted growth (Kessing and Mau 2007). Indirect damage also occurs through the excretion of excess sugars as honeydew, which accumulates on the upper surface s of leaves and supp orts the growth of sooty mold. This can hinder photosynthetic activity and reduce fruit quality ( Capinera 2009).

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22 One of the major problems with aphids is that the y transmit plant virus es. Aphid transmitted viruses affecting zucchini squash include the cucumovirus Cucumber mosaic virus (CMV), and the potyviruses Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), and Papaya ringspot virus watermelon strain (PRSV W) (Webb et al. 2003, Summers e t al. 2004, Frank and Liburd 2005). During periods of high infestations, plants can become stunted and yield fewer fruits compared with healthy plants. In addition, fruits harvested from infected plants are frequently deformed and mottled, rendering them u nmark etable (Blua and Perring 1989). Blua and Perring (1989) reported that as much as 80% of the crop can be lost if squash plants infected with ZYMV are left untreated. Aphids have the ability to transmit these plant viruses in a non persistent manner , w stylet s while feeding on an infected plant and transferred to a healthy plant during the next feeding or probing ( Castle et al. 1992, Perring et al. 1992 ). Aphids are efficient vectors of viruses. Ap hids are able to acquire viruses in as little as 8 s of probing and can transmit them in less than 4 s (Kucharek and Purcifull 2001). In addition to their ability to reproduce rapidly and reach high numbers in a short period of time, alate aphids are capab le of movement from one location to another, feeding on a number of plants in a short period of time, thus aiding in the transmission of viruses (Kucharek and Purcifull 2001). Lecoq et al. (1981) reported that M. persicae and A. gosspyii can transmit ZYMV at a frequency of 70 90% with three viruliferou s aphids per plant. These aphid transmitted viruses can cause significant yield reduction and substantial monetary losses.

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23 Whiteflies Another significant pest of squash are whiteflies (Hemiptera: Aleyrodida e), which are minute phloem feeding insects generally characterized by having wings covered with wax. The silverleaf whitefly, Bemisia tabaci B biotype, is considered one of the most noxious insect pests attacking ornamentals, vegetable, and agronomic cro ps in tropical and subtropical regions of the world (Chen et al. 2004). Bemisia tabaci has a wide host range and can reproduce on over 500 different plant species (Greathead 1986), including some 30 cash and staple crops worldwide, such as tomato, pepper, melon, watermelon, soybean, cotton, and b eans (Hilje and Stansly 2008). The silverleaf whitefly was first reported in 1986 to be a significant pest on poinsettias in Florida, but soon became a major pest of vegetables in south and central parts of Florid a (Hilje et al. 2001). The first report of economic damage associated with silverleaf whitefly in cucurbits was recorded in Florida i n 1988 (Schuster et al. 1991). Today, B. tabaci is considered an important economic pest and a vector of viruses and plan t transmitted diseases in cucurbits. The whitefly life cycle comprises an egg, four nympha l ins tars, and a winged adult. Female whiteflies deposit eggs singly on the undersides of leaves, in part because of a negative geotropic response (Cardoza et al. 2000). Upon eclosion, a scale mouthparts and begin feeding ( Schuster et al. 1991 ). The mobile first instar stage is followed by three sessile nymphal instars (Jones 2003). Development time fr om egg to adult is approximately 2 to 3 w at optimal temperatures (25 30 ° C ) ( Gerling 1990 ), and adults can live up to several weeks ( Byrne and Bellows 1991 ).

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24 Whiteflies generally present a greater problem during the fal l squash crop, particularly in north c entral Florida, since whitefly populations peak in late summer. Similarly, in west c entral Florida, sticky trap catches of adult silverleaf whiteflies have been greatest in the summer and late fall ( Schuster et al. 1992 ). Whit eflies cause direct damage to cucurbits through feeding, su cking the sap from the phloem. Whiteflies also excrete a sticky substance known as honeydew, a sugar rich substrate that promotes the growth of sooty mold on leaf surfaces and can reduce photosynt hesis (Jones 2003, Chen et al. 2004). A significant concern for growers is the ability of B. tabaci to transmit numerous plant pathogenic viruses and induce plant physiological disorders (Chen et al. 2004), causing significant yield losses. The Cucurbit leaf crumple virus (CuLCrV), recently reported from Florida (Akad et al. 2008, Nyoike et al. 2008), is a geminivirus transmitted by B. tabaci . Infected plants have crumpled, curled, and thickened leaves (Akad et al. 2008). During periods of high infestatio ns, plants can become stunted and yield fewer fruits compared with healthy plants. Akad et al. (2008) reported i ncidences of plants symptomatic for CuLCrV were greater than 95% in three squash fields that were sampled in central Florida in 2008. The silver leaf whitefly transmits geminiviruses to cucurbits in a persistent manner, such that once the virus is acquired by the whitefly it retain s the ability to transmit it for a long period of time. Therefore, silverleaf whiteflies are not only responsible for transmitting plant viruses to healthy plants within the same crop (Manandhar et al. 2009), but have the potential to infect new plant species as a result of their broad host range (Jones 2003).

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25 In addition to transmitting viruses, a significant concern f or cucurbit producers is that the silverleaf whitefly also damages the plant by inducing a physiological disorder ( Yokomi et al. 1990 ). One of the most damaging plant physiological disorders in cucurbits is the sq uash silverleaf (SSL) disorder. SSL is as sociated with the feeding of immature silverleaf whiteflies, and is characterized by silvering of the upper leaf surface and irregular ripening of fruit ( Yokomi et al. 1990 , Costa et al. 1993 ). SSL symptoms can develop in as little as 14 d ( Costa et al. 1 993 ). The disorder first manife sts as yellowing of leaf veins. As the symptoms progress, veins begin to appear silver, and under severe infestations, the entire upper leaf surface is si lvered (McAuslane et al. 2004). The silver appearance is due to the separation of the upper epidermis from the palisade cells below the epidermis, which allows for the formation of an air space within the mesophyll and palisade cell l ayers (McAuslane et al. 2004). Leaves affected by SSL have lower chlorophyll content and higher light reflectance than normal leaves, which can reduce photosynthetic ability (Cardoza et al. 2000). Photosynthesis in completely silvered leaves is 30% lower than in healthy leaves, which may result in lower productivity by the plant (Cardoza et a l. 2000). Depending on the severity of SSL disorder, the quality of fruit can be reduced, rendering it unmarketable and resulting in severe yield losses ( Costa et al. 1994 ). Using Insecticides to Manage Insect Pest Populations in Organic Squash Insectici des are used in conventional systems to constrain the proliferation of persistently transmitted viruses by preventing pest population build up on the host (Palumbo et al. 2001, Nyoike and Liburd 2010). Conventional cucurbit producers use soil applications of imidacloprid [Admire ® Pro (Bayer Cropscience, Research Triangle

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26 Park, NC )] to manage aphid and silverleaf whi tefly populations (Seal 2008). Imidacloprid is a neonicotinoid insecticide that is systemic in plants and can be applied to the soil (Palumbo et al. 2001). Its use has been associated with enhanced yields and quality, and reductions in systemic feeding disorders in variou s crops (Palumbo et al. 2001). Imidacloprid can also be used in conjunction with mulches to enhance its effect on aphids and w hiteflies (Nyoike et al. 2008, Nyoike and Liburd 2010). However, overdependence on insecticides has resulted in resistant populations to selected classes of insecticides . Resistance to organophosphate, carbamate, organochlorine, and pyrethroid insecticides has been reported in A. gossypii in field grown cucurbits ( Hollingsworth et al. 1994 ). Aphid and whitefly species have also demonstrated potential resistance to neonicotinoids, which is a relatively newer class of insecticides (Foster et al. 2002; Nauen e t al. 2002). There are several pesticides that have been approved for pest management in organic cucurbit production. These organically approved pesticides include a zadirachtin based products (Aza Sol ® , Aza Direct ® ), pyrethrins (PyGanic ® ), insecticidal soa ps (M Pede ® ), and spinosad (Entrust ® ). Azadirachtin is a neem derived botanical insecticide that acts as an insect feeding deterrent and growth regulator ( Pedigo and Rice 2009 ). Azadirachtin blocks the synthesis and release of molting hormones leading to i ncomplete ecdysis in immature insects (Dayan et al. 2009). In adult females, a similar mechanism of action leads to sterility (Dayan et al. 2009). Pyrethrins are derived from chrysanthemums (Asterales: Asteraceae) and are approved for use as a broad spectr um insecticide. Pyrethrin is a contact poison that causes a neurotoxic reaction in the pest, resulting in hyperexcitation, convulsions, seizures, and

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27 eventually death (Dayan et al. 2009). Insecticidal soaps are made from the salts of fatty acids a nd act as a contact poison; therefore , they must be directly applied to the insect to be effective (Buss and Park Brown 2002). The above mentioned products are recommended for control of insect pests such as aphids and whiteflies in organic squash. Spinosad, althou gh not recommended for aphid and whitefly control, is a common product used in organic vegetable production for the control of caterpillars, leaf miners, thrips, and foliage feeding beetles (Dayan et al. 2009). Spinosad is derived from the soil actinomycet e bacterium, Saccharopolyspora spinosa, nervous system by disrupting acetylcholine neurotransmission (Dayan et al. 2009). Since aphid and whitefly adults are continually colonizing fields and moving between plants, frequent appl ications of foliar sprays may be required to prevent pest population buildup and to reduce the spread of insect transmitted viruses (Pa lumbo et al. 2001). With regard to aphids, the application of contact and systemic insecticides to manage aphid populatio ns provides insufficient control because aphids acquire and transmit viruses in a short period of time, usually before the aphid vector acquires a lethal insecticide dose (Summers et al. 2004). Furthermore, the use of contact insecticides to manage these p ests is problematic because all life stages occur on the underside of leaves (Nyoike and Liburd 2010). Although insecticides can provide some control for aphid and whitefly populations, the use of insecticides is not always successful when applied as a si ngle strategy. It will be important to reduce our dependence on insecticides and incorporate more integrated pest management (IPM) strategies in order to reduce the incidence of

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28 insect transmitted plant viruses , delay the development of resistance in pest populations , and conserve natural enemies. Integrated Pest Management Strategies The widespread practices of planting crops in monoculture, as well as the development of resistance among insect pests due to persistent applications of insecticides with simi lar modes of action , have been given as reasons for pest populations and their associated viruses becoming significant problem s in agriculture (Jones 2003). Alternatives to insecticides are needed to conserve natural enemies and delay the development of r esistance in pest populations. Several studies have shown that aphid and whitefly populations are reduced in mixed cropping systems and crops interplanted with nonhost cover crops or mu lches (Manandhar et al. 2009). These studies support the idea that no nhost crops planted within the same field as the cash crop can serve as habitats for conserving and increasing populations of natural enemies , thereby introducing diversity into agroecosystems for improved pes t control (Platt et al. 1999). An integrated a pproach involving the use of a reduced risk insecticide, in combination with the augmentation and conservation of biological control and the implementation of mulches within the cucurbit field , may provide a more sustainable approach for aphid and whitefly population control, as well as insect transmitted disease management. Biological Control Naturally occurring beneficial organisms in the field serve as an important control tactic for managing aphid and whitefly populations. Predators of aphids and whit eflies include adults and larvae of ladybird beetles (Coleoptera: Coccinellidae), larvae of

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29 hoverflies (Diptera: Syrphidae), gall midge larvae (Diptera: Cecidomyiidae), lacewing larvae (Neuroptera: Chrysopidae), minute pirate bugs (Hemiptera: Anthocoridae) , carabids (Coleoptera: Carabidae), and spiders (Arachnida) (Schmidt et al. 2003, Luc as 2005, McNeill et al. 2012). Phytoseiid mites are also known as predators of immature whitefly stages, and some of these predacious mite populations are maintained in a n agroecosystem by feeding on pollen from host and nonhost plants (Nomikou et al. 2001, Inbar and Gerling 2008). Whitefly specialist parasitoids, including Encarsia formosa Gahan , Encarsia luteola Howard , and Eretmocerus californicus Howard (Hymenoptera: Aphelinidae) have been fairly successful in the greenhouse; however , there are few cases of success reported from augmented populations released under field condit ions (Liburd and Nyoike 2008). McNeill et al. (2012) recorded several aphid parasitoids in s quash plots, including Aphelinus sp p . (Hymenoptera: Aphelinidae) and several braconid species: Aphidius sp p ., Chelonus sp p ., and Lysiphlebus testaceipes (Cress on) (Hymenoptera: Braconidae). Some of these parasitoids were implicated in the suppression of a phid populations in more diversified cropping systems, where squash was planted as the main crop. Relatively high numbers of aphid mummies were also recorded in the squash plots during the same sampling period (McNeill et al. 2012). The coccinellid beetle Delphastus catalinae (Horn), has been cited as a good biological control candidate for whiteflies as a result of high prey consumption rates, long adult lives, and high fecund ity rates (Heinz et al. 1999). D elphastus catalinae is an obligate whitefly predator ( Gordon 1994) and larvae are known to consume approximately 167 eggs per day and up to 1000 eggs before pupating (Hoelmer et al. 1993). D elphastus catalinae larvae have also been observed feeding on honeydew,

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30 even when abundant whiteflies were available (Liu and St ansly 1999). This suggests that availability of other alternate food sources might allow these predators to survive periods of low prey density. Heinz et al. (1999) demonstrated that adult beetles released from a central point source dispersed less than 1m /d at high prey dens ities. This low propensity to disperse suggests that movement of D. catalinae out of experimental plots should be minimal. Synthetic Mulches Mulches (i.e., synthetic mulches, living mulches) have been effective in reducing aphid an d whitefly populations on squash plants, resulting in a lower incidence of insect transmitted diseases (Hooks et al. 1998, Summers et al. 2004, Frank and Liburd 2005, Nyoike and Liburd 2010). UV reflective mulch reflects short wave light, which acts to rep el incoming aphids and whiteflies ( Smith et al. 1964 ). UV reflective mulch can be used to manipulate insect vision interfering with host finding, landing, and orientation thus reduc ing pest populations on host plants (Diaz and Fereres 2007). UV reflective materials are commonly used as mulches for open grown crops, or as plastic sheets or screens for protected crops (Diaz and Fereres 2007). Zalom (1981) reported on the successful application of aluminum foil mulches within experimental lettuce plantings, such that aphid populations and the incidence of aphid transmitted viruses w ere dis Summers et al. (2004) found that colonization by t he silverleaf whitefly and the incidence of aphid transmitted diseases were reduced in zucchini squash plots covered with UV reflective mulch compared with unmulched plots. Furthermore, Chen et al. (2004) reported that pumpkin, cucumber, and zucchini crop s

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31 planted with UV reflective mulches yielded more than plants in bare soil. However, the high costs associated with the removal of synthetic silver plastic materials each growing season is an economic concern for growers (Hilje et al. 2001, Frank and Libur d 2005, Adkins et al. 2011). Habitat Manipulation and Living Mulches Habitat manipulation provides another opti on to reduce pest populations. Habitat manipulation involves providing an unfavorable environment for insect pests and often a more favorable en vironment for their natural enemies, for instance, by introducing plants that provide food, shelter and oviposition sites for natural enemies (Landis et al. 2000). Providing a wide array of diverse resources and refuges in these systems will promote the d iversity of natural enemy and herbivorou s insect populations. This in turn will introduce increased predation, parasitism, and competition for resources in order to suppress the build up and outbreaks of insect pest species. Increasing vegetational divers ity within an agroecosystem is one method for enhancing natural enemy abundance and diversity. Vegetational diversity within an agroecosystem can either be accomplished by intercropping two crops within one agricultural field, or planting a crop with a be neficial noncrop (Andow 1991). In the latter instance, the noncrop is usually termed a cover crop or a living mulch. Noncrop vegetation may provide increased resources such as alternative prey and hosts, as well as pollen and nectar for parasitoids and p redators (Altieri 1999). Parasitoids and predators often commute between insect host containing and plant food containing areas (Marino and Landis 1996).

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32 Living mulches are plants grown within a main crop to reduce erosion (Langdale et al. 1991), suppress weed germination and growth (Teasdale and Mohler 1993), and recycle excess nut rients (Prasifka et al. 2006). Living mulches can also serve to reduce pest populations by cr eating a more diverse community; therefore, reducing the host the pest (the resource concentration hypothesis; Root 1973) or attracting natural enemies of the pests (the natural enemies hypothesis; Root 1973) (Bugg 1991, Hooks et al. 1998, Nyoike and Liburd 2010). Several studies have evaluated living mulches for c ontrol of aphids and whiteflies and demonstrated successful reduction in pest population densities while delaying the onset and spread of associated insect transmitted viruses (Frank and Liburd 2005, Hooks and Wright 2008). Living mulches act to decrease t he chance of appropriate landings on host plants by aphid and whitefly pests by reducing the contrast between bareground and the main crop (Prokopy and Owens 1983). Aphid densities are frequently lower in crops incorporating living mulches (Costello 1994, Costello and Altieri 1995, Vidal 1997, Hooks et al. 1998, Frank and Liburd 2005, Hooks and Wright 2008). For instance, Costello and Altieri (1994) investigated broccoli production in a living mulch system utilizing legum es and found that white clover, Tri folium repens L. , living mulch reduced th e density of the cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae) , compare d with a broccoli monoculture. They concluded that the lower numbers in the living mulch plots were due to the lower light intensities reflected from the living mulch (Costello and Altieri 1994). Living mulches provide food resources (i.e., honey, pollen) and shelter for natural enemies that could contribute to the reduction of pest populations ( Root 1973 ). Frank

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33 and Liburd (2005) demonstrated that li ving mulch treatments in zucchini squash had higher natural enemy populations than the synthetic mulch and bareground treatments. Predator populations including spiders (Hooks and Johnson 2004), carabid beetles (Prasifka et al. 2006), and hover flies (Vida l 1997) have been reported to be greater in cropping systems where living mulches have been incorporated. Zhao et al. (1992) found greater densities of pupae of the parasitoid Cotesia rubecula (Marshall) (Hymenoptera: Braconidae) in broccoli interplanted w ith nectar producing plants than in broccoli monoculture. Buckwheat, Fagopyrum esculentum Moench (Caryophyllales: Polygonaceae) is commonly used in southeast organic production systems as a cover crop to suppress weeds and replace bare fallow (Clark 2007 ) . B uckwheat has also been cited as an important living mulch in cucurbit production systems (Hooks et al. 1998, Frank and Liburd 2005). Significant reductions in pest densities have been recorded when buckwheat was intercropped into squash pr oduction systems. In Hawaii, Hooks et al. (1998) found buckwheat to be an effective companion plant in suppressing aphids, aphid transmitted viruses and whiteflies on zucchini squash when compared with zucchini in bare ground treatments. Frank and Liburd (2005) also found a reduction in aphid and whitefly densities in zucchini grown with buckwheat compared with bareground treatments. Hooks et al. (1998) and Hooks and Wright (2008) reported reduced SSL disorder symptoms on zucchini squash plants in buckwhea t mulch treatments compared to bareground plots. also attract beneficial insects that attack or parasiti ze aphids and whiteflies . These benefic ials include hover flies , predatory wasps, minute pirate bugs, and lady beetle s.

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34 Flowering may start within three weeks of planting and continue for up to 10 weeks (Clark 2007) . Some debate exists as to whether living mulch or synthetic mulch systems offer the best potential for management of whiteflies and aphids (Frank and Libu rd 2005). Frank and Liburd (2005) reported that although the costs of living mulches were less than synthetic mulches, they required additional upkeep and management, such as watering and weeding. Nyoike and Liburd (2010) found that zucchini plants int erplanted with buckwheat were smaller in size and eventually yielded less compared with zucchini growing on the synthetic mulches due to compet ition for light and nutrients. However, synthetic reflective mulches can lose their efficacy as shade from the c rop canopy increases ( Csizinsky et al. 1997 ). The fact that there are negative attributes such as competition and establishment costs associated with living mulches should be weighed against the positive benefits of using living mulches (i.e., enhancing n atural enemy populations, recycling nutrients) to determine if use of such mulch in cropping systems is justifiable (Hooks et al. 1998). Furthermore, adjustments in planting space and time may increase marketable yields, but more research is needed in this area. The implementation of mixed cropping systems and crops interplanted with alternative host cover crops has the potential to reduce aphid and whitefly populations, as well as the impact of insect transmitted viruses, on cucurbits (Hooks et al. 1998, N yoike and Liburd 2010). However, different intercropping arrangements of buckwheat within squash need to be evaluated in order to maximize marketable yields in squash. Furthermore, enhanced pest suppression can be achieved by incorporating various control tactics, such as the augmentation of biological controls and the use of

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35 organically approved pesticides, which can be used in conjunction with living mulches to maximize marketable yields for organic growers. Research addressing the effectiveness of organi cally approved insecticides for managing pest populations in squash as well as their effects on natural enemies will provide additional information on how these management tactics can be incorporated with a buckwheat living mulch to effectively suppress pe st and disease incidence while increasing marketable yields in organic squash production.

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36 CHAPTER 3 PREFERENCE OF THE SILVERLEAF WHITEFLY ON ZUCCHINI SQUASH AND BUCKWHEAT AND THE EFFECT OF DELPHASTUS CATALINAE Zucchini squash, Cucurbita pepo L., is a high value vegetable crop in Flo rida (Nyoike and Liburd 2010). However, plant physiological disorders and plant viruses transmitted by the silverleaf whitefly, Bemisia tabaci B biotype, are serious problems for many sq uash growers around the state. One o f the most damaging plant physiological disorders in squash is squash silverleaf (SSL) disorder, which is associated with the feeding of immature silverleaf whiteflies ( Yokomi et al. 1990, Costa et al. 1993 ). SSL is characterized by silvering of the upper leaf surface and blanching of fruit, which can reduce the quality of the fruit produced depending on the severity of the disorder ( Costa et al. 1994, Cardoza et al. 2000, McAuslane et al. 2004 ). In addition to plant physiological disorders, Cucurbit leaf crumple virus is a n important whitefly transmitted virus that was first recorded in Florida during the f all 2006 and has the potential to cause significant squash yield losses ( Akad et al. 2008, Nyoike et al. 2008). Several studies have shown that white fly populations are reduced in mixed cropping systems and in crops interplanted with nonhost cover crops or mulches (Hooks et al. 1998, Frank and Liburd 2005, Manandhar et al. 2009). Living mulches decrease the whitefly densities on host plants by reducin g the contrast between bareground and the plant canopy (Liburd and Nyoike 2008). Additionally, nonhost crops planted within the same field as the cash crop can serve as habitats for conserving and increasing populations of natural enemies, therefore, intro ducing diversity into agroecosystems for improved pest control (Platt et al. 1999). The coccinellid beetle Delphastus catalinae (Horn) has been cited as a good biological control candidate for whiteflies (Heinz et al. 1999, Liu and Stansly 1999).

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37 Delph astus catalinae is an obligate whitefly predator with high pr ey consumption rates. L arvae are known to consume an average of 167 eggs per day and up to 1000 eggs before pupating (Hoelmer et al. 1993). Delphastus catalinae also exhibits long adult lives and high fecundity rates (Heinz et al. 1999). Legaspi et al. (2006) observed that D. catalinae displayed a preference for whiteflies in the egg stage, followed by small then large nymphs. They suggested that D. catalinae would be effective early in the season when eggs are abundant. Liu and Stansly (1999) observed that some D. catalinae larvae fed on honeydew and dew drops, and the availability of alternate food sources may enhance survival and discourage dispersal of the natural enemy. Buckwheat , Fagopyrum es culentum Moench , has been cited as an important living mulch in cucurbit production systems (Hooks et al. 1998, Frank and Liburd 2005). Significant reductions in pest densities have been recorded when buckwheat was intercropped into squash production syst ems when compared with zucchini in bare ground treatments (Hooks et al. 1998, Frank and Liburd 2005 ). Buckwheat is an annual plant that completes its life cycle in Florida in 6 weeks (Frank and Liburd 2005). Buckwheat also flowers profusely and attracts beneficial insects to the cucurbit crop (Platt et al. 1999, Frank and Liburd 2005). Attraction of natural enemies of whiteflies may be an important advantage of implementing buckwheat mulches, such that natural enemies can play an important role in pest r eduction. The implementation of cultural control techniques in agriculture, such as the augmentation and conservation of biological control and the implementation of living mulches, has the potential to reduce whitefly numbers as well as the impact of SS L disorder and other whitefly transmitted viruses on cucurbits. The purpose of this study

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38 was to investigate the effect of a living mulch and a natural enemy on silverleaf whitefly population densities in zucchini squash. The specific objectives were : 1 ) to evaluate the effect of buckwheat as a living mulch on whiteflies when interplanted with zucchini squash, and 2) to assess the impact of Delphastus catalinae on whitefly populations in buckwheat and zucchini squash. Materials and Methods Experiments were con ducted during the spring of 2011 and 2012 in the Small Fruit and Vegetable IPM greenhouse in the Department of Entomology and Nematology, Universit y of Florida, Gainesville, FL. Experimental design was a split plot design with four replicates to test the effects of a predator, D. catalinae , on whitefly populations on zucchini squash and buckwheat . The main plot treatments were presence or absence of D. catalinae and subplot treatments were zucchini squash and buckwheat. C hoice test s were conducted to deter mine preference of silverleaf whiteflies when exposed to zucchini squash and buckwheat. Squash and buckwheat plants were grown in the greenhouse in 1 L pots. Zucchini squash seeds were directly seeded, whereas buckwheat seeds were planted in a seed tray and transplanted after two weeks into 1 L pots. T wo 1 m 3 locally made whitefly exclusion cages containing zucchini squash and buckwheat plants were used for this study . E ach cage contained eight plants, such that four zucchini squash plants and four buckwheat plants were distributed randomly within each cage . Adult whiteflies and D. catalinae were obtained from a colony maintained on cotton and collards in the Small Fruit and Vegetable IPM laboratory. Delphastus catalinae adults were originally purchased from Bicontrol Network, LLC (Brentwood, TN)

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39 and maintained on a colony of silverleaf whiteflies. The colony was with 70±5% RH on L:D 14:10 in the Department of Entomology and Nematology, Universit y of Florida, Gainesville, FL. C age s 1 and 2 w ere infested with 25 adult whiteflies per cage on 8 March 2011 and 27 March 2012. The adult whiteflies we re allowed to reproduce for approximately 1 w before cage 1 w as infested w ith adult D. catalinae . Initially, 30 D. catalinae adults were released on 16 March 2011 to observe the effect of predation on whitefly population densit ies. During pre trial o bservations of D. catalinae , the adult beetles demonstrated high dispersal rates from coll ards infested with whiteflies. Therefore, we infested cage 1 with a high number of D. catalinae adults relative to the number of whiteflies present in the cage. Howe ver, the following year the release of D. catalinae was reduced to 10 adults per cage to approximate a 1:10 predator to prey ratio. Cage 2 did not receive any D. catalinae and only contained whiteflies . Plants were watered as needed, given fertilizer N P K 10:10:10 , and fungicide labeled for use on squash was used to control the incidence of powdery mildew on plants in the greenhouse . Data were recorded every 3 d from 11 March 2011 to 22 April 2011 and 30 March 2012 to 7 May 2012 (approximately 6 w ). T he number of whitefly adults, 1 st instars, and 2 nd 4 th instars on each plant was observed by visual inspection by turning over each leaf and using a magnifying glass within the cage . In cage 1, the number of D. catalinae adults on each plant w as also recorded . The data w ere analyzed using the repeated m easures analysis of variance procedure ( AN O VA; PROC GLM , SAS Institute 2009) to investigate insect population density over time. Sample date was the repeated measure and t reatment means were separated by least significant differences (LSD)

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40 test (SAS Institute 2009). Differences among treatments were considered significant if P 0.05. Results In 2011, adult whitefly densities were different between plant treatments ( F = 101.49 ; df = 1, 194 ; P , D. catalinae treatments ( F = 22. 1 5; df = 1, 19 4 ; P 0.0001) , and there was an interaction effect ( F = 19.79 ; df = 1, 19 4 ; P 0.0001) . A dult whitefl y densities were greater on zucchini squash compared with buckwheat (Fig. 3 1) . F ewer adult whiteflies w ere recorded on squash in treatments with D. catalinae compared with treatments without D. catalinae . T here was no significant difference in adult whitefly densities on buckwheat when comparing the D. catalinae treatments (Fig. 3 1) . A dult whitefly densiti es were also different over time ( F = 14.12 ; df = 1 4 , 194 ; P 0.0001) and there was a plant treatment × time interaction effect ( F = 14.10 ; df = 1 4 , 19 4 ; P 0.0001) , such that treatment differences were observed in the final two weeks of sampling . There was also a predator × time interaction effect ( F = 3.09 ; df = 1 4 , 19 4 ; P = 0.000 2 ) , such that treatment differences were observed in the final two weeks of sampling . In 2012, adult whitefly densities were different between plant treatments ( F = 90.77 ; df = 1, 181 ; P D. catalinae treatments ( F = 56.37 ; df = 1, 1 81 ; P 0.0001) , and there was an interaction effect ( F = 35.50 ; df = 1, 1 81 ; P 0.0001) . S imilar to 2011, more adult whiteflies were recorded on zucchini squash compared with buckwheat (Fig. 3 2) . In addition, fewer adult whiteflies were recorded in treatments with D. catalinae compared with treatments without D. catalinae (Fig. 3 2). A dult whitefly densities were also different over time ( F = 11.37 ; df = 1 3 , 181 ; P

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41 was a plant treatment × time interaction effect ( F = 9.38 ; df = 1 3 , 1 81 ; P 0.0001) , such that treatment differences were observed in the final two weeks of sampling . There was also a predator × time interaction effect ( F = 6.51 ; df = 1 3 , 1 81 ; P 0.000 1 ) , such that treatment differences were observed in the final t wo weeks of sampling . In 2011, 1 st instar immature whitefly densities were different between plant treatments ( F = 34.39 ; df = 1, 194 ; P D. catalinae treatments ( F = 7.94 ; df = 1, 194 ; P = 0.00 53 ) , and there was a n interaction effect ( F = 8.49 ; df = 1, 194 ; P = 0.00 40 ) . There were more 1 st instar immature whiteflies on zucchini squash compared with buckwheat (Fig. 3 3) . F ewer 1 st instar immature whiteflies were recorded on zucchini squash in treatments with D. catalinae compared with treatments without D. catalinae ; however , there was no significant difference in whitefly densities on buckwheat when comparing the D. catalinae treatments (Fig. 3 3) . First instar immature whitefly densities were also different over time ( F = 6.88 ; df = 1 4 , 194 ; P there was a plant treatment × time interaction effect ( F = 6.11 ; df = 1 4 , 1 94 ; P 0.0001) , such that treatment differences were observed in the third and sixth week of sampling . There was also a predator × time interaction effect ( F = 2.00 ; df = 1 4 , 19 4 ; P = 0.0 193 ) , such that treatment differences were observed in the third and sixth week of sampling . In 2012, 1 st instar immature whitefly densities were different between plant treatments ( F = 38.54 ; df = 1, 181 ; P D. catalinae tr eatments ( F = 22.69 ; df = 1, 181 ; P 0.00 01 ) , and there was a n interaction effect ( F = 15.37 ; df = 1, 181 ; P = 0.00 01 ). There were more 1 st instar immature whiteflies on zucchini squash compared with buckwheat (Fig. 3 4) . F ewer 1 st instar immature white flies were recorded on zucchini squash in treatments with D. catalinae compared with treatments without D.

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42 catalinae ; however , there was no significant difference in whitefly densities on buckwheat when comparing the D. catalinae treatments (Fig. 3 4) . Fir st instar immature whitefly densities were also different over time ( F = 4.84 ; df = 1 3 , 181 ; P there was a plant treatment × time interaction effect ( F = 4.98 ; df = 1 3 , 1 81 ; P 0.0001) , such that treatment differences were observed from the third week until the sixth week of sampling . There was also a predator × time interaction effe ct ( F = 3.19 ; df = 1 3 , 1 81 ; P = 0.000 2 ) , such that treatment differences were observed from the fourth until the sixth week of sampling . In 2011, 2 nd 4 th instar immature whitefly densities were different between plant treatments ( F = 33.39 ; df = 1, 1 94 ; P D. catalinae treatments ( F = 26.18 ; df = 1, 1 94 ; P 0.00 01 ) , and there was a n interaction effect ( F = 8.75 ; df = 1, 1 94 ; P = 0.00 35 ) . There were fewer 2 nd 4 th instar immature whiteflies on zucchini squash in treatments with D. catalinae comp ared with treatments without D. catalinae (Fig. 3 5) . There were also fewer 2 nd 4 th instar immature whiteflies on buckwheat in treatments with D. catalinae compared with treatments without D. catalinae (Fig. 3 5) . Second 4 th instar immature whitefly d ensities were also different over time ( F = 4.10 ; df = 1 4 , 194 ; P plant treatment × time interaction effect ( F = 2.59 ; df = 1 4 , 1 94 ; P = 0.00 19 ) , such that treatment differences were observed in the last three weeks of sampling . There was also a predator × time interaction effect ( F = 1.90 ; df = 1 4 , 19 4 ; P = 0.0 286 ) , such that treatment differences were observed in the final two weeks of sampling . In 2012, 2 nd 4 th instar immature whitefly densities were different between plant treatments ( F = 68.92 ; df = 1, 181 ; P D. catalinae treat ments ( F = 44.67 ; df =

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43 1, 181 ; P 0.00 01 ) , and there was a n interaction effect ( F = 22.48 ; df = 1, 181 ; P 0.00 01 ). There were more 2 nd 4 th instar immature whiteflies on zucchini squash compared with buckwheat (Fig. 3 6). F ewer 2 nd 4 th instar immatur e whiteflies were recorded on zucchini squash in treatments with D. catalinae compared with treatments without D. catalinae ; however , there was no significant difference in whitefly densities on buckwheat when comparing the D. catalinae treatments (Fig. 3 6). Second 4 th instar immature whitefly densities were also different over time ( F = 10.64 ; df = 1 3 , 181 ; P plant treatment × time interaction effect ( F = 10.41 ; df = 1 3 , 1 81 ; P 0.00 01 ) , such that treatment differences were observed in the last two weeks of sampling . There was also a predator × time interaction effect ( F = 3.52 ; df = 1 3 , 1 81 ; P 0.000 1 ) , such that treatment differences were observed from the third to the six week of sampling . In 2011, D. catalinae densities were different between plant treatments ( F = 36.25 ; df = 1, 7 8 ; P 0.0001) , over time ( F = 7.13 ; df = 1 2 , 7 8 ; P 0.0001) , and there was a treatment × time interaction effect ( F = 3.21 ; df = 1 2 , 7 8 ; P 0.0001) , such that treatment differences were observed the first two weeks of sampling. M ore D. catalinae were observed on zucchini squash compared with buckwheat (Fig. 3 7) . In 2012, D. catalinae densities were not significantly different between plant treatments ( F = 0.14 ; df = 1, 6 6 ; P = 0.708 1 ) or over time ( F = 0.32 ; df = 1 0 , 66 ; P = 0. 9720 ) , and there was no interaction effect ( F = 1.04 ; df = 1 0 , 66 ; P = 0. 420 9 ) (Fig. 3 8). Discussion W hitefly densities were higher on zucchini squash when compared with buckwheat plants. The finding suggests that buckwheat is not an attractive host for

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44 silverleaf whiteflies, and therefore supports the recommendation by Hooks et al. (1998) and Frank and Liburd (2005) that buckwheat could serve as an important living mulch in cucurbit production systems. T he introduction of D. catalinae on zucchini squash reduces whitefly populations, due to its high prey consumption rates of imma ture whiteflies as reported by Heinz et al. (1999). In the absence of D. catalinae , whitefly populations on squash increased exponentially at the end of the six week sampling period. For the first three weeks during the sampling period, adult whiteflies we re not affected by the presence of D. catalinae , which is consistent with observations that the predatory beetle does not feed on the adult stages of the silverleaf whitefly. By the end of the sampling period, squash treatments where D. catalinae was absen t had more adult whiteflies compared with treatments where D. catalinae was present. This finding also correlates with a greater density of immature whitef lies on plants where D. catalinae was absent. Therefore, more adults were able to emerge from survivi ng immature stages where D. catalinae was absent. In general, significant difference s in whitefly densities were not recorded a mong the buckwheat treatments. Since whitefly populations remained low on buckwheat plants, it was difficult to observe a differ ence in whitefly densities on buckwheat when D. catalinae was introduced. An exception to this rule was the significant reduction in 2 nd 4 th instar immature whitefly densities on buckwheat with D. catalinae when compared with whitefly densities on buckw heat without D. catalinae . This suggests that D. catalinae can also be an efficient predator on buckwheat. In 2011, more adult D. catalinae were found on squash where the whitefly density was greater compared with buckwheat. Heinz et al. (1999) indicate d that when

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45 D. catalinae locates its host at high densities, the propensity to disperse is low. In 2012, there was no difference in adult D. catalinae distribution between squash and buckwheat over the six week sampling period. This finding is not consiste nt with the finding from 2011, and could possibly be explained by fewer adult D. catalinae being released in 2012 (10 adults/cage ) compared with 2011 (30 adults/cage ) and therefore significant differences in distribution were more difficult to demonstrate. There were also more immature whiteflies present on plants in 2012 compared with 2011 , because there were fewer adult D. catalinae present in 2012 compared with 2011. This may have influenced D. catalinae distribution and could suggest that there may be a saturation limit of the pest that may influence D. catalinae dispersal. In conclusion, D. catalinae when used in conjunction with buckwheat as a living mulch could aid in the reduction of whiteflies on zucchini squash and possibly reduce the incidence of whitefly transmitted diseases. Future studies should consider the effect of intercropping buckwheat with zucchini squash on populations of silverleaf whiteflies and D. catalinae . The efficacy of this study in the greenhouse will hopefully support the feasibility of intercropping buckwheat with zucchini squash in the field, releasing D. catalinae as a biological control to reduce populations of silverleaf whiteflies, and enhance the sustainability of cucurbit production systems.

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46 Figure 3 1. Mean ( ± SE) number of ad ult whiteflies observed over a six week period for the whitefly preference study in spring 2011 on four treatments: buckwheat without D. catalinae , buckwheat with D. catalinae , squash without D. catalinae , and squash with D. catalinae . Arrow indicates when D. catalinae were released. 0 10 20 30 40 50 60 70 80 90 Mean # of adult whiteflies/plant Buckwheat with D. catalinae Squash with D. catalinae Buckwheat without D. catalinae Squash without D. catalinae

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47 Figure 3 2. Mean ( ± SE) number of adult whiteflies observed over a six week period for the whitefly preference study in spring 2012 on four treatments: buckwheat without D. catalinae , buckwheat with D. catalinae , squas h without D. catalinae , and squash with D. catalinae . Arrow indicates when D. catalinae were released. 0 20 40 60 80 100 120 140 160 Mean # of adult whiteflies/plant Buckwheat with D. catalinae Squash with D. catalinae Buckwheat without D. catalinae Squash without D. catalinae

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48 Figure 3 3. Mean ( ± SE) number of 1 st instar immature whiteflies observed over a six week period for the whitefly preference st udy in spring 2011 on four treatments: buckwheat without D. catalinae , buckwheat with D. catalinae , squash without D. catalinae , and squash with D. catalinae . Arrow indicates when D. catalinae were released. 0 20 40 60 80 100 120 Mean # of 1st instar whiteflies/plant Buckwheat with D. catalinae Squash with D. catalinae Buckwheat without D. catalinae Squash without D. catalinae

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49 Figure 3 4. Mean ( ± SE) num ber of 1 st instar immature whiteflies observed over a six week period for the whitefly preference study in spring 2012 on four treatments: buckwheat without D. catalinae , buckwheat with D. catalinae , squash without D. catalinae , and squash with D. catalina e . Arrow indicates when D. catalinae were released. 0 50 100 150 200 250 300 350 Mean # of 1st instar whiteflies/plant Buckwheat with D. catalinae Squash with D. catalinae Buckwheat without D. catalinae Squash without D. catalinae

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50 Figure 3 5. Mean ( ± SE) number of 2 nd 4 th instar immature whiteflies observed over a six week period for the whitefly preference study in spring 2011 on four treatments: buckwheat wi thout D. catalinae , buckwheat with D. catalinae , squash without D. catalinae , and squash with D. catalinae . Arrow indicates when D. catalinae were released. 0 20 40 60 80 100 120 Mean # of 2nd 4th instar whiteflies/plant Buckwheat with D. catalinae Squash with D. catalinae Buckwheat without D. catalinae Squash without D. catalinae

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51 Figure 3 6. Mean ( ± SE) number of 2 nd 4 th instar immature whiteflies observe d over a six week period for the whitefly preference study in spring 2012 on four treatments: buckwheat without D. catalinae , buckwheat with D. catalinae , squash without D. catalinae , and squash with D. catalinae . Arrow indicates when D. catalinae were rel eased. 0 50 100 150 200 250 300 350 Mean # of 2nd 4th instar whiteflies/plant Buckwheat with D. catalinae Squash with D. catalinae Buckwheat without D. catalinae Squash without D. catalinae

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52 Figure 3 7. Mean ( ± SE) number of D. catalinae observed over a six week period for the whitefly preference study in spring 2011 on buckwheat and squash. 0 1 2 3 4 5 Mean # of D. catalinae /plant Buckwheat Squash

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53 Figure 3 8. Mean ( ± SE) number of D. catalinae obser ved over a six week period for the whitefly preference study in spring 2012 on buckwheat and squash. 0 0.5 1 1.5 2 2.5 Mean # of D. catalinae /plant Buckwheat Squash

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54 CHAPTER 4 INVESTIGATING VARIOUS TACTICS OF INTERCROPPING BUCKWHEAT WITH SQUASH TO REDUCE PEST S AND DISEASE INCIDENCE AND INCREASE YIELD Aphids (Hemipte ra: Aphididae) and the silverleaf whitefly, Bemisia tabaci B biotype (Hemiptera: Aleyrodidae) are major pests of zucchini squash, Cucurbita pepo L., and plant physiological disorders and insect transmitted diseases are serious problems for many growers thr oughout the state of Florida . During the fall season, aphid s and whiteflies can reach high population densities ( Schuster et al. 1992 ) and after infected individuals enter a field they can transmit and spread viruses very quickly (Jones 2003). Aphid tr ansmitted viruses affecting zucchini squash include Cucumber mosaic virus (CMV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), and Papaya ringspot virus watermelon strain (PRSV W) (Webb et al. 2003, Summers et al. 2004, Frank and Libu rd 2005). Cucurbit leaf crumple virus (CuLCrV) is a whitefly transmitted virus that has the potential to cause significant squash yiel d losses (Nyoike et al. 2008). One of the most damaging plant physiological disorders in squash is squash silverleaf (SSL ) disorder, which is associated with the feeding of immature whiteflies ( Yokomi et al. 1990 ). SSL is characterized by silvering of the upper leaf surface, which can reduce the quality of the fruit produced depending on the severity of the disorder ( Costa et al. 1994, Cardoza et al. 2000, McAuslane et al. 2004 ). The use of insecticides, such as imidacloprid, can be an important management tactic for suppressing aphid and whitefly populations on squash, hindering the proliferation of viruses within the fie ld and transmission among plants (Nyoike and Liburd 2010). However, sustainable manage ment of aphids and whiteflies with insecticid al tactics can be problematic for several reasons , including their location on

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55 the underside of the leaf (Nyoike and Liburd 2 010), their ability to transmit viruses quickly (Summers et al. 2004), and the potential for insecticide resistance to develop in these pest populations (Foster et al. 2002; Nauen et al. 2002). Furthermore, the majority of chemical management tactics for p est control in zucchini squash is developed for conventional growers and a number of these products are not compliant with the . Research based recommendations on organic pest management are limited and sometimes unavailable for many growers through typical information channels . There is a need to incorporate integrated pest management (IPM) strategies that are compatible with organic production systems for the benefit of all farmers interested in sustainable agriculture . The implementation of cultural control techniques in agriculture, such as the use of mixed cropping systems and crops interplanted with non host cover crops or living mulches, when used in conjunction with other pest suppression methods has the potential to re duce pest populations and the incidence of insect transmitted viruses (Frank and Liburd 2005, Manandhar et al. 2009 , Nyoike and Liburd 2010 ). Several studies evaluating the efficacy of buckwheat as a living mulch in squash production systems for the contr ol of aphids and whiteflies have demonstrated successful pest suppression, as well as lower incidences of insect transmitted viruses (Hooks et al. 1998, Frank and Liburd 2005, Nyoike and Liburd 2010 ). In addition, flowering buckwheat attracts beneficial in sects to the cucurbit crop (Frank and Liburd 2005). Attraction of natural enemies of aphid and whitefly pests may be an important advantage of implementing buckwheat mulches, such that natural enemies can play an important role in pest reduction.

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56 Naturall y occurring beneficial organisms in the field serve as an important control tactic for managing aphid and whitefly populations. Predators of aphids and whiteflies include adults and larvae of ladybird beetles (Coleoptera: Coccinellidae), larvae of hoverfli es (Diptera: Syrphidae), gall midge larvae (Diptera: Cecidomyiidae), lacewing larvae (Neuroptera: Chrysopidae), minute pirate bugs (Hemiptera: Anthocoridae), carabids (Coleoptera: Carabidae), and spiders (Arachnida) (Schmidt et al. 2003, Lucas 2005, McNeill et al. 201 2). Specialist parasitoids of whiteflies include Encarsia formosa Gahan , Encarsia luteola Howard , and Eretmocerus californicus Howard (Hymenoptera: Aphelinidae) (Liburd and Nyoike 2008). McNeill et al. (2012) recorded several aphid parasitoids in squash pl ots, including Aphelinus sp p . (Hymenoptera: Aphelinidae) and several braconid species: Aphidius sp p ., Chelonus sp p ., and Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae). The coccinellid beetle Delphastus catalinae (Horn) has been cited as a good biological control candidate for whiteflies as a result of high prey consumption rates, long adult lives, and high fecundity rates (Heinz et al. 1999). Liu and Stansly (1999) also observed that some D. catalinae larvae fed on honeydew and dew drops, a nd the availability of this and other alternate food sources may enhance survival and discourage dispersal of the natural enemy. A more sustainable approach is needed to address the limitations of the current management strategy, which relies heavily on in secticides to manage aphids and whiteflies and the dis eases they transmit in squash. The use of buckwheat as a living mulch intercropped with squash has shown promise to reduce pest and disease pressure while increasing the abundance of beneficial insects (Hooks et al. 1998,

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57 Nyoike et al. 2008, Nyoike and Liburd 2010). However, squash yields can be significantly reduced when buckwheat is used as a living mulch , most likely due to early season competition for mineral salts and water (Nyoike and Liburd 2010 ). Adjustments in plant spacing and time of planting may increase marketable yields, but more research is needed in this area. The purpose of this study was to evaluate several methods of intercropping buckwheat and squash to develop a cropping system that reduces pest s and disease incidence whil e increasing marketable yield. The specific objectives were : 1) to compare several tactics of intercropping buckwheat and squash and their effects on pest and natural enemy densities, disease incidence, and marketa b le yields in field grown squash; 2) to incorporate a key natural enemy, D. catalinae , into buckwheat and squash crops to determine the effects on pest po pulations and marketable yields; and 3) to use an on farm demonstration model to implement the buckwhe at squash intercropping tactic while incorporating D. catalinae in to Materials and Methods Plot Preparation and Experimental Design Comparing tactics for intercropping buckwheat into squash production system while incorporating D. catalin ae . This experiment was conducted during the fall of 2011 and 2012 at the University of Florida Plant Science Research and Education Unit (PSREU) at Citra, FL. Experimental p lots contained 4 rows per plot and measured 7.6 m x 7.6 m. Plots were separated b y 4.5 m of bare s oil on all sides. P lanting beds were raised and prepared using a tractor , and each bed received two drip irrigation lines . Zucchini squash variety

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58 selected because it is a high yielding squash vari ety and it is disease resistant to some strains of Zucchini yellow mosaic virus . Zucchini squash was hand seeded on 8 September 2011 and 10 September 2012. Plant spacing was approximately 30.5 cm between squash plants . M issing plants were replaced after germ ination using squash transplants that were previously established in the greenhouse . Selected Seeds, Winslow, ME) was hand seeded 10 d and 3 d before planting the squash seeds in 2011 and 2012, respectively. In 2011, buckwheat was plant ed 7 d earlier than the squash and greater competition between buckwheat and the squash was observed ; therefore, the planting days were reduced from 10 to 3 prior to planting squash in 2012 . In 2011, b uckwheat seeds were sown by hand in a continuous line a long the length o f the bed. As a result, buckwheat density was high in 2011 and buckwheat plants had to be thinned out to reduce competition between buckwheat and squash. In 2012, buckwheat seeds were sown by hand every 1.27 cm . In 2011, the experimental d esign consisted of a randomized complete block with four replicates of five treatments . Treatments included the following planting arrangements : 1) buckwheat alternating where 2.5 m strips of buckwheat and bare ground were alternating on either side of s quash planted in the middle of the bed ; 2) buckwheat alternating with D. catalinae , which was planted identical to the first treatment and D. catalinae was released into the plot; 3) buckwheat in the middle where buckwheat was planted in the middle of the bed with squa sh planted on both sides; 4) buckwheat in the middle with D. catalinae , which was identical to the third treatment and D. catalinae was released into the plot; and 5) buckwheat on both sides served as a control with solid rows of buckw heat growin g on both sides of the squash

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59 (Fig. 4 1) . This was the standard treatment that was previously evaluated in Nyoike and Liburd (2010), where yield was lower in squash due to competition from buckwheat. rre d t o as buckwheat arrangement A, , and the was referred to as buckwheat arrangement C . The same arrangements were used in 2012; however a sixth tre atment was added, bareground which served as a control with squash planted in the middle of the bed without any buckwheat present in the plot. Consequently , in 2012, there were six treatments with four replicates arranged in a randomized complete block des ign. In treatments where D. catalinae was present, 100 adults were released into each plot approximately two and a half w eeks after the squash was planted to ensure that adult whiteflies had sufficient time to colonize and reproduce. Delphastus catalinae adults were originally purchased from Bicontrol Network, LLC (Brentwood, TN) and maintained on a colony of silverleaf whiteflies infesting cotton and collards in the Small on L:D 14:10 in the Department of Entomology and Nematology, University of Florida, Gainesville, FL. On farm demonstration to intercrop buckwheat into squash production system while incorporating D. catalinae . This study was conducted during the fall of 20 13 at an organic farm in north c entral FL. Experimental design was a completely randomized design with three treatments and three replicates. Experimental plots contained 4 rows per plot and measured 4 m x 4 m . Plots were separated by 4. 5 m of bare soil on all sides. Planting beds were prepared using a tractor and each bed

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60 received two drip irrigation lines. Squash was hand seeded approximately 30.5 cm apart on 6 September 2013. Two of the three treatments had the yellow summer squash variety Zephyr® (Joh , Winslow, ME ) . The third treatment was a grower standard consisting of three mixed squash varieties : Sunburst® patty , Winslow, ME ), Eight Ball® zucchini , Wi nslow, ME ), and One Ball® zucchini squash , Winslow, ME ). After germination, missing plants were replaced using squash transplants that were previously established in the greenhouse. Buckwheat ) was hand seeded 2 d before planting the squash. Buckwheat seeds were planted approximately 1.27 cm apart . Three treatments were evaluated and involved the following planting arrangements : 1) buckwheat arrangement A where 1.3 m strips of buckwheat and bar eground were alternating on either side of summer squash ; 2) buckwheat arrangement B where buckwheat was planted in the middle of the bed with squash planted on both sides ; and 3) mixed v arieties with three differe nt varieties of squash randomly mixed and planted on both sides of the bed and otherwise surrounded by baregr ound with no buckwheat planted. Fifty adult D. catalinae were obtained from the colony previously described and released in plots where buckwheat w as planted approximately two and a half weeks after planting squash to ensure that adult whiteflies had sufficient time to colonize and reproduce. Agronomic practices for organic squash production in all three years were adapted from the standard producti on guide for squash in North Florida (Olson et al. 2012). Dipel DF® (Valent BioSciences Corporation, Libertyville, IL) and Entrust® (Dow

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61 Agrosciences LLC, Indianapolis, IN) were rotated and applied during the growing season for the control of melonworm, Di aphania hyalinata Linnaeus and pickleworm, Diaphania nitidalis (Stoll) (Lepidoptera: Pyralidae) . The fungicides Serenade® Max (AgraQuest Inc., Davis, CA) and Regalia® (Marrone Bio Innovations, Davis, CA) w ere sprayed as required against powdery mildew. A b lended dry granular fertilizer compliant with organic systems [ Nature Safe (10 2 8) (Griffin Industries LLC, Cold Spring, KY) ] was incorporated into the soil at planting and followed by a second application of the same f ertilizer four weeks after planting. Weed management was maintained mechanically as required throughout the growing season. Sampling Alate and apterous aphids, adult and immature whiteflies, disease incidence, natural enemies, plant size, and marketable yield in each plot were monitored and recorded as described below . Aphids. Alate and apterous aphids, both immatures and adults, were sampled from randomly selected plants in the outer rows of each plot using the leaf turn method as detailed in Nyoike and Liburd (2010). In 2011 and 2012, nine random plants were selected and in 2013, five random plants were selected. Leaf turn sampling occurred weekly. Alate aphids were also monitored using blue colored pan traps ( Solo , Lake Forest, IL ) that were secured within tomato cages and contained appro ximately 250 cm 3 of 5% detergent solution (Colgate Palmolive Co., New York, NY). Two traps were placed in each plot at opposing corners in 2011 and 2012, and one trap was placed in each plot in 2013. The contents of the traps were collected weekly and take n back to

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62 the University of Florida Small Fruit and Vegetable IPM laboratory in Gainesville, FL where the number of alate aphids were counted and recorded. Whiteflies. Adult whiteflies were monitored using yellow sticky Pherocon® AM unbaited traps (YST) (Great Lakes IPM, Vestaburg, MI) that were mounted on wooden stakes and placed just above the plant canopy . T wo t raps were placed in the inner rows of each plot at opposing ends in 2011 and 2012, and one t rap was placed in the inner row s of each plot in 20 13. Traps were left in the field for 24 h, after which t he number of adult whiteflies per trap was counted at the Small Fruit and Vegetable IPM laboratory in Gainesville, FL. For the purpose of sampling immature whiteflies, three of the nine l eaves used fo r sampling apterous aphids in 2011 and 2012, and two of the five leaves used for sampling apterous aphids in 2013, were excised and brought back to the laboratory in Gainesville, FL. A 3.14 cm 2 leaf disc was taken from each leaf using a cork borer. The num ber of immature whiteflies was counted using a dissecting microscope and recorded. Diseases. Visual observations of viral symptoms and incidence were monitored each week by recording the number of plants in eac h plot showing virus s ymptoms. Leaves were c ollected and assayed for the most commonly occurring aphid transmitted cucurbit viruses by a double antibody sandwich enzyme linked immunosorbent assay (DAS ELISA) as detailed by Clark and Adams (1977). Leaves were also assayed using polymerase chain react ion (PCR) techniques to confirm the presence of the whitefly transmitted Cucurbit leaf crumple virus (CuLCrV) as d etailed in Akad et al. (2008). Squash silverleaf (SSL) was also monitored eac h week. Ten p lants were randomly selected from the inner rows o f each plot in 2011 and 2012, and five plants were

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63 randomly selected from the inner rows of each plot in 2013. Plants were scored with an arbitrary scale adapted from Yokomi et al. (1990) that ranges from 0, which indicates a healthy plant, to 5, which ind icates a plant with all leaves completely silvered . Natural enemies. Natural enemies were mo nitored each week using in situ counts. Six p lants were randomly selected from the outside rows of each plot in 2011 and 2012, and three plants were randomly sel ected from the outside rows of each plot in 2013 . The numbers of predators and parasitoids on each plant were counted and recorded. Natural enemies were also monitored using pitfall traps containing a 5% detergent solution (Colgate Palmolive Co. , New Yor k, NY) and the YST used to monitor adult whiteflies . Two pitfall traps were placed in the inner rows of each plot in opposing corners in 2011 and 2012, and one trap was placed in the inner rows in 2013. YST were left in the field for 24 h and pitfall trap s were left in the field fo r 1 w . Traps were collected weekly and taken back to the University of Florida Small Fruit and Vegetable IPM laboratory in Gainesville, FL where natural enemies were identified and recorded. Plant measurements and marketabl e yields. Squash plant height and width was measured each week from ten randomly selected plants in the inner rows of each plot in 2011 and 2012, and five randomly selected plants in 2013, using a technique adopted from Frank and Liburd (2005). Plant heig ht was measured from the ground to the terminal bud with a tape measure. Plant width was measured along the length between the two widest opposing lateral shoots. Squash was harvested fro m the inner rows of each plot. Marketable fruit was harvested and we ighed in the field every other day until the end of the season. Fruit was determined to be marketable by examin ing the fruit for evidence of viral symptoms or physiological disorders, suc h as irregular fruit

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64 ripening, as well as pest damage from pickleworm and wet rot of fruits caused by fungus. Data Analysis Aphid, whitefly, natural enemy, disease incidence, and plant measurement data were analyzed by repeated measures analysis of variance procedure ( ANOVA; PROC GLM, SAS Institute 2009). The model was cons tructed to examine the main effect of treatment by date, and block was designated as a random factor. Marketable yield data were summed over the entire growing season and analyzed using ANOVA (PROC GLM, SAS Institute 2009). Within the model, the following preplanned orthogonal contrasts were conducted: buckwheat arrangement A versus buckwheat arrangement B, buckwheat arrangement A versus buckwheat arrangement C , buckwheat arrangement B versus buckwheat arrangement C , buckwheat arrangement A versus baregroun d, buckwheat arrangement B versus bareground, buckwheat arrangement C versus bareground, buckwheat arrangement A versus mixed varieties, and buckwheat arrangement B versus mixed varieties. Treatments with identical buckwheat arrangements were also compared to evaluate the influence of released D. catalinae on pest populations and yields. Aphid, whitefly, and n atural enemy counts were square root transformed, and disease incidence and marketable yield data were log transformed to stabilize variances . Reporte d means are from non transformed data. Treatment means were separated by least significant differences (LSD) test (SAS Institute 2009), and differences among treatments were considered significant if P 0.05.

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65 Results Aphids In the studies conducted at the PSR E U ( 2011 ) , aphid densities sampled by in situ counts were different over time ( F = 73.79; df = 4, 830; P there was no significant treatment ( F = 1.84; df = 4, 830; P = 0.1196) or int eraction effect ( F = 1.28; df = 16, 830; P = 0.2034) (Fig. 4 2 ) . Aphid densities observed in pan trap counts were different by treatment ( F = 2.80; df = 4, 165; P = 0.0279) and over time ( F = 20.02; df = 4, 165; P teraction effect ( F = 1.54; df = 16, 165; P = 0.0900). Aphid densities were observed to be greater in buckwheat arrangement B treatments compared with buckwheat arrangement A treatments ( F = 9.36; df = 1, 165; P = 0.0026) and the buckwheat arrangement C tr eatment ( F = 5.20; df = 1, 165; P = 0.0239) (Fig. 4 3 ). In 2012, aphid densities sampled by in situ counts were different by treatment ( F = 3.00; df = 5, 1050; P = 0.0107) and over time ( F = 5.98; df = 4, 1050; P there was no significant int eraction effect ( F = 1.30; df = 20, 1050; P = 0.1700). Aphid densities were observed to be less in the buckwheat arrangement C treatment compared with buckwheat arrangement A treatments ( F = 5.42; df = 1, 1050; P = 0.0201), buckwheat arrangement B treatmen ts ( F = 7.15; df = 1, 1050; P = 0.0076), and the bareground treatment ( F = 13.91; df = 1, 1050; P = 0.0002) (Fig. 4 4 ). Aphid densities were also less in buckwheat arrangement A compared with the bareground treatment ( F = 3.92; df = 1, 1050; P = 0.0481) (F ig. 4 4 ). Aphid densities observed in pan trap counts were different over time ( F = 5.22; df = 4, 210; P = 0.0005) but there

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66 was no significant treatment ( F = 0.52; df = 5, 210; P = 0.7605) or interaction effect ( F = 0.87; df = 20, 210; P = 0.6286) (Fig. 4 5 ). In the on farm study ( 2013 ) , aphid densities sampled by in situ counts were different by treatment ( F = 5.25 ; df = 2 , 210 ; P = 0.00 60 ), over time ( F = 5.54 ; df = 4, 210 ; P = 0.000 3 ), and there was a n interaction effect ( F = 3.31 ; df = 8 , 210 ; P = 0.0 01 4 ) such that treatment differences were observed in the fourth and fifth week s of sampling. There were fewer aphids found on squash plants in the mixed varieties treatment compared with the buckwheat arrangement A treatment ( F = 6.73 ; df = 1, 210 ; P = 0 .0 102 ) and the buckwheat arrangement B treatment ( F = 8.87 ; df = 1, 210 ; P = 0.00 32 ) (Fig. 4 6 ). Aphid densities observed in pan trap counts were not significantly different by treatment ( F = 0.24 ; df = 2 , 30 ; P =0. 7844 ) or over time ( F = 1.68 ; df = 4, 30 ; P = 0. 1805 ), and there was no interaction effect ( F = 0.36 ; df = 8 , 30 ; P = 0. 9346 ) (Fig. 4 7 ). Whiteflies In 2011, immature whitefly count s from leaf disc assays were different by treatment ( F = 3.04; df = 4, 260; P = 0.0180), over time ( F = 74.62; df = 4 , 260; P 0.0001), and there was an interaction effect ( F = 1.72; df = 16, 260; P = 0.0439) such that treatment differences were observed the first week of sampling. Immature whitefly populations were estimated to be less in buckwheat arrangement A treatm ents compared with the buckwheat arrangement C treatment ( F = 11.69; df = 1, 260; P = 0.0007) (Fig. 4 8 ). Adult whitefly densities counted from yellow sticky traps were different over time ( F = 72.83; df = 4, 165; P there was no significant treatment ( F = 1.58; df = 4, 165; P = 0.1826) or interaction effect ( F = 0.56; df = 16, 165; P = 0.9086) (Fig. 4 9 ).

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67 In 2012, immature whitefly count s from leaf disk assays were different by treatment ( F = 3.50; df = 5, 330; P = 0.0042), over time ( F = 20 .02; df = 4, 330; P 0.0001), and there was an interaction effect ( F = 1.79; df = 20, 330; P = 0.0202), such that treatment differences were observed the first, third, and fourth week s of sampling. Immature whitefly populations were estimated to be less in the bareground tre atment compared with treatments with buckwheat, including buckwheat arrangement A treatments ( F = 14.59; df = 1, 330; P = 0.0002), buckwheat arrangement B treatments ( F = 12.79; df = 1, 330; P = 0.0004), and the buckwheat arrangement C treatment ( F = 7.54; df = 1, 330; P = 0.0064) (Fig. 4 10 ). Adult whitefly densities counted from yellow sticky traps were different over time ( F = 90.14; df = 5, 252; P there was no significant treatment effect ( F = 1.76; df = 5, 252; P = 0.1219) (Fig. 4 11 ). In 2013, immature whitefly count s from leaf disk assays in the on farm demonstration were different by treatment ( F = 19.02 ; df = 2 , 75 ; P over time ( F = 2.73 ; df = 4, 75 ; P = 0.0 350 ), and there was an interaction effect ( F = 2.60 ; df = 8 , 75 ; P = 0.0 144 ) such that treatment differences were observed in all but the second week of sampling. There were fewer immature whiteflies assayed from the mixed varieties treatment compared with the buckwheat arrangement A treatment ( F = 31.23 ; df = 1, 75 ; P the buckwheat arrangement B treatment ( F = 25.54 ; df = 1, 75 ; P (Fig. 4 12 ). Adult whitefly densities counted from yellow stic ky traps were different over time ( F = 6.85 ; df = 4, 30 ; P = 0.000 5 ), but there was no significant treatment ( F = 2.28 ; df = 2 , 30 ; P = 0. 1201 ) or interaction effect ( F = 1.39 ; df = 8 , 30 ; P = 0.2420) (Fig. 4 13 ).

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68 Diseases Samples obtained from the field and tested for viruses were predominately found to test positive for Cucurbit leaf crumple virus using PCR techniques in all three years. Although not prevalent in the field, several leaf samples tested positive for Zucchini yellow mosaic virus and Papaya ringspot virus w atermelon strain using ELISA techniques in 2011 and 2012, but not in 2013 at the on farm demonstration trial . In 2011, virus incidence was different over time ( F = 12.35; df = 4, 70; P 0.0001) but there was no significant treatment ( F = 1.08; df = 4, 70; P = 0.3710) or interaction effect ( F = 0.71; df = 16, 70; P = 0.7785) (Fig. 4 14 ). SSL ratings were different by treatment ( F = 2.51; df = 4, 925; P = 0.0407) and over time ( F = 258.68; df = 4, 925; P on effect ( F = 0.68; df = 16, 925; P = 0.8123). SSL ratings were greater in the buckwheat arrangement C treatment compared with buckwheat arrangement A treatments ( F = 8.18; df = 1, 925; P = 0.0043) and buckwheat arrangement B treatments ( F = 6.04; df = 1 , 925; P = 0.0142) (Fig. 4 15 ). In 2012, virus incidence was different by treatment ( F = 8.07; df = 5, 90; P 0.0001) and over time ( F = 15.39; df = 4, 90; P effect ( F = 0.62; df = 20, 90; P = 0.8873). There were m ore plants showing virus symptoms in the bareground treatment compared with treatments with buckwheat, including buckwheat arrangement A treatments ( F = 37.17; df = 1, 90; P buckwheat arrangement B treatments ( F = 9.02; df = 1, 90; P = 0.0034), and the buckwheat arrangement C treatment ( F = 11.58; df = 1, 90; P = 0.0010) (Fig. 4 16 ). There were also fewer plants showing virus symptoms in buckwheat arrangement A compared with plants in buckwheat arrangement B ( F = 14.35; df = 1, 90; P = 0.0003)

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69 an d buckwheat arrangement C ( F = 4.70; df = 1, 90; P = 0.0329) (Fig. 4 16 ). SSL ratings were different by treatment ( F = 4.96; df = 5, 1170; P = 0.0002), over time ( F = 221.93; df = 4, 1170; P interaction effect ( F = 2.85; df = 20, 1170; P fourth, and fifth week s of sampling. SSL ratings were lower in the bareground treatment compared with trea tments with buckwheat, including buckwheat arrangement A treatments ( F = 13.12; df = 1, 1170; P = 0.0003), buckwheat arrangement B treatments ( F = 18.27; df = 1, 1170; P buckwheat arrangement C treatment ( F = 5.91; df = 1, 1170; P = 0.01 52) (Fig. 4 17 ). In 2013, virus incidence was different by treatment ( F = 7. 85 ; df = 2 , 30 ; P = 0.00 18 ) and over time ( F = 7.73 ; df = 4, 30 ; P = 0.000 2 ), but there was no interaction effect ( F = 0.2 9 ; df = 8 , 30 ; P = 0.9 636 ). There were more plants showin g virus symptoms in the buckwheat arrangement A treatment compared with the buckwheat arrangement B treatment ( F = 7.43 ; df = 1, 30 ; P = 0.0 106 ) and the mixed varieties treatment ( F = 14.84 ; df = 1, 30 ; P = 0.000 6 ) (Fig. 4 18 ). SSL ratings were different b y treatment ( F = 127.72 ; df = 2 , 210 ; P F = 18.38 ; df = 4, 210 ; P 0.0001), and there was an interaction effect ( F = 5.27 ; df = 8 , 210 ; P treatment differences were observed in all weeks sampled. SSL ratings were lower in the mixed varieties treatment compared with the buckwheat arrangement A treatment ( F = 234.97 ; df = 1, 210 ; P the buckwheat arrangement B treatment ( F = 134.13 ; df = 1, 210 ; P (Fig. 4 19 ). SSL ratings were also lower in the buckwheat arrangement B treatment compared with the buckwheat arrangement A treatment ( F = 14.04 ; df = 1, 210 ; P = 0.0002) (Fig. 4 19 ).

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70 Natural Enemies The natural enemies observed by in situ counts for all three years included green lacewings (Neuropte ra: Chrysopidae); lady beetles (Coleoptera: Coccinellidae); ground beetles (Coleoptera: Carabidae); hover flies (Diptera: Syrphidae); big eyed bugs, Geocoris sp p . (Hemiptera: Lygaeidae); minute pirate bugs, Orius sp p . (Hemiptera: Anthocoridae); and spiders (Araneae). In 2011, lacewing densities observed by in situ counts were different by treatment ( F = 6.90; df = 4, 355; P 0.0001) and over time ( F = 13.54; df = 4, 355; P F = 1.09; df = 16, 355; P = 0.3634). Lacewing densities were greater in buckwheat arrangement A compared with buckwheat arrangement B treatments ( F = 4.46; df = 1, 355; P = 0.0353) and the buckwheat arrangement C treatment ( F = 4.30; df = 1, 355; P = 0.0388) (Table 4 1). Lacewing densities w ere also greater in treatments where D. catalinae was not released compared with treatments where D. catalinae was released ( F = 12.93; df = 1, 355; P = 0.0004) (Table 4 1). Orius densities observed by in situ counts were different by treatment ( F = 4.96; df = 4, 355; P = 0.0007), over time ( F = 17.83; df = 4, 355; P 0.0001), and there was an interaction effect ( F = 2.79; df = 16, 355; P = 0.0003), such that treatment differences were observed on the second week of sampling. Orius densities were greater i n the buckwheat arrangement C treatment compared with both buckwheat arrangement A ( F = 18.29; df = 1, 355; P 0.0001) and buckwheat arrangement B treatments ( F = 10.53; df = 1, 355; P = 0.0013) (Table 4 1). In 2012, lacewing densities observed by in sit u counts were different by treatment ( F = 3.79; df = 5, 690; P = 0.0021), over time ( F = 31.99; df = 4, 690; P

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71 0.0001), and there was an interaction effect ( F = 1.57; df = 20, 690; P = 0.0530), such that treatment differences were observed the third and fourth weeks of sampling. Lacewing densities were less in the bareground treatment compared with buckwheat arrangement B treatments ( F = 6.08; df = 1, 690; P = 0.0139) (Table 4 2) . Lacewing densities were also less in the buckwheat arrangement C treatment compared with buckwheat arrangement A ( F = 8.80; df = 1, 690; P = 0.0031) and buckwheat arrangement B treatments ( F = 13.87; df = 1, 690; P = 0.0002) (Table 4 2) . Geocoris densities were different by treatment ( F = 8.66; df = 5, 690; P F = 87.41; df = 4, 690; P n interaction effect ( F = 6.92; df = 20, 690; P weeks of sampling. Geocoris densities were less in the b areground control compared with all buckwheat treatments, including buckwheat arrangement A ( F = 4.23; df = 1, 690; P = 0.0400) , buckwheat arrangement B ( F = 29.40; df = 1, 690; P and buckwheat arrangement C ( F = 18.46; df = 1, 690; P (Table 4 2) . Geocoris densities were also less in buckwheat arrangement A compared with buckwheat arrangement B ( F = 16.98; df = 1, 690; P and buckwheat arrangement C ( F = 8.43; df = 1, 690; P = 0.0038) (Table 4 2). In the on farm demonstration plot ( 2013 ) , there were no significant differences in the mean number of natural enemy taxa observed during in situ counts among treatments. The natural enemies collected from the yellow sticky traps include lady beetles (Coleoptera: Coccinellidae); minute pirate bugs, Orius sp p . (Hemiptera: Anthocoridae); hover flies (Diptera: Syrphidae); and several parasitoids including Aphelinus sp p .

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72 (Hymenoptera: Aphelinidae); Encarsia sp p . (Hymenoptera: Aphelinidae); Eretmocerus sp p . (Hymenoptera: Aphelinidae); and Tr ichogramma sp p . (Hymenoptera: Trichogrammatidae). In 2011, Eretmocerus densities were different by treatment ( F = 3.23; df = 4, 165; P = 0.0140), and over time ( F = 34.93; df = 4, 165; 0.0001), but there was no interaction effect ( F = 1.07; df = 16, 1 65; P = 0.3861). There were fewer Eretmocerus parasitoids recorded in buckwheat arrangement B compared with buckwheat arrangement A ( F = 10.93; df = 1, 165; P = 0.0012) and buckwheat arrangement C ( F = 5.99; df = 1, 165; P = 0.0154) (Table 4 3). Trichogram ma densities were different by treatment ( F = 2.80; df = 4, 165; P = 0.0279), and over time ( F = 49.82; df = 4, 165; 0.0001), but there was no interaction effect ( F = 1.24; df = 16, 165; P = 0.2395). There were more Trichogramma parasitoids recorded in buckwheat arrangement A compared with buckwheat arrangement B ( F = 4.66; df = 1, 165; P = 0.0324) and buckwheat arra ngement C ( F = 7.27; df = 1, 165; P = 0.0078) (Table 4 3). In 2012, Encarsia densities were different by treatment ( F = 3.74; df = 5, 252; P = 0.0028), and over time ( F = 38.22; df = 5, 252; 0.0001), but there was no interaction effect ( F = 1.05; df = 25, 252; P = 0.4029). There were more Encarsia parasitoids recorded in buckwheat arrangement B compared with buckwheat arrangement A ( F = 4.45; df = 1, 252; P = 0.0359), buckwheat arrangement C ( F = 12.69; df = 1, 252; P = 0.0004), and the bareground trea tment ( F = 8.04; df = 1, 252; P = 0.0049) (Table 4 4). Trichogramma densities were different by treatment ( F = 11.31; df = 5, 252; P 0.0001), over time ( F = 44.47; df = 5, 252; 0.0001), and there was a n interaction effect ( F = 2.40; df = 25, 252; P = 0.0003), such that treatment differences were

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73 observed in all sampling weeks except the first week. There were more Trichogramma par asitoids recorded in the bareground control compared with all buckwheat treatments, including buckwheat arrangement A ( F = 33.23; df = 1, 252; 0.0001), buckwheat arrangement B ( F = 52.50; df = 1, 252; 0.0001), and buckwheat arrangement C ( F = 31.17; df = 1, 252; 0.0001) (Table 4 4). In the on farm demonstration plot ( 2013 ) , there were no significant differences in the mean number of natural enemy taxa collected from yellow sticky traps among treatments. The natural enemies collected from pitfall traps include ground beetles (Coleoptera: Carabidae); big eyed bugs, Geocoris sp p . (Hemiptera: Lygaeidae); minute pirate bugs, Orius spp. (Hemiptera: Anthocoridae); and spiders (Araneae) . In 2011 and 2013, there were no significant differences in the mean number of predator taxa collected from pitfall traps among treatments. In 2012, ground beetle densities were different by treatment ( F = 3.18; df = 5, 210; P F = 10.29; df = 4, 210; 0.0001), but there was no interaction effect ( F = 1.54; df = 20, 210; P = 0.0695). There were fewer ground beetles in the bareground treatment compared with all buckwheat treatments, including buckwheat arrangement A ( F = 14.89; df = 1, 210; P = 0.0002), buckwheat arrangement B ( F = 8.25; df = 1, 210; P = 0.0045), and buckwheat arrangement C ( F = 7.38; df = 1, 210; P = 0.0072) (Table 4 5). Plant Measurements and Marketable Yields In 2011, zucchini plant height (cm) was different by treatment ( F = 18.64; df = 4, 935; P F = 143.61; df = 4, 935; P n interaction effect ( F = 8.89; df = 16, 935; P

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74 were observed the first two weeks of sampling. Zucchini plant height was less in buckwheat arrangement B treatments compared with buckwheat arrangement A treatments ( F = 60.31; df = 1, 935; P buckwheat arrangement C treatment ( F = 32.35; df = 1, 935; P 20 ). Zucchini plant width (cm) was also different by treat ment ( F = 32.89; df = 4, 935; P F = 104.43; df = 4, 935; P F = 1.44; df = 16, 935; P = 0.1138). Similar to observations recorded on plant height, zucchini plant width was less in buck wheat arrangement B compared with buckwheat arrangement A ( F = 85.26; df = 1, 935; P buckwheat arrangement C ( F = 83.53; df = 1, 935; P ) (Fig. 4 21 ). In 2012, zucchini plant height was different by treatment ( F = 9.19; df = 5, 1170; P F = 704.11; df = 4, 1170; P n interaction effect ( F = 2.14; df = 20, 1170; P = 0.0025), such that treatment differences were observed the second, third, and fourth weeks of sampling. Zucchini plant height was greater in the buckwheat arrangement C treatment compared with buckwheat arrangement A ( F = 4.19; df = 1, 1170; P = 0.0408), buckwheat arrangement B ( F = 8.84; df = 1, 1170; P = 0.0030), and the bareground treatment ( F = 35.20; df = 1, 1170; P ) (Fig. 4 22 ). Additionally, plant height was less in the bareground treatment compared with buckwheat arrangement A ( F = 23.07; df = 1, 1170; P buckwheat arrangement B ( F = 15.04; df = 1, 1170; P = 0.0001) (Fig. 4 22 ). Zucchini plant width w as different by treatment ( F = 11.97; df = 5, 1170; P time ( F = 71.47; df = 4, 1170; P F = 0.81; df = 20, 1170; P = 0.7083). Zucchini plant width was less in the buckwheat arrangement

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75 C tre atment compared with buckwheat arrangement A ( F = 34.04; df = 1, 1170; P 0.0001), buckwheat arrangement B ( F = 9.64; df = 1, 1170; P = 0.0020), and the bareground treatment ( F = 34.39; df = 1, 1170; P 4 23 ). Zucchini plant width was also less in buckwheat arrangement B compared with buckwheat arrangement A ( F = 11.18; df = 1, 1170; P = 0.0009) and the bareground treatment ( F = 13.45; df = 1, 1170; P = 0.0003) (Fig. 4 23 ). In 2013, squash plant height was different by treatment ( F = 13.13 ; df = 2 , 210 ; P F = 61.65 ; df = 4, 210 ; P n interaction effect ( F = 4.07 ; df = 8 , 210 ; P = 0.000 2 ), such that treatment differences were observed the fourth and fifth weeks of sampling. Squash plant height was less in the mi xed varieties treatment compared with buckwheat arrangement A ( F = 25.64 ; df = 1, 210 ; P and buckwheat arrangement B ( F = 10.34 ; df = 1, 210 ; P = 0.00 15 ) (Fig. 4 24 ). Squash plant width was different by treatment ( F = 37.01 ; df = 2 , 210 ; P 01), over time ( F = 12.45 ; df = 4, 210 ; P n interaction effect ( F = 2.25 ; df = 8 , 210 ; P = 0.0 250 ), such that treatment differences were observed in all weeks except the first week of sampling. Squash plant width was less in the m ixed varieties treatment compared with buckwheat arrangement A ( F = 68.58 ; df = 1, 210 ; P buckwheat arrangement B ( F = 4.50 ; df = 1, 210 ; P = 0.0 351 ) (Fig. 4 25 ). Squash plant width was also less in buckwheat arrangement B compared with buckw heat arrangement A ( F = 37.95 ; df = 1, 210 ; P 0.0001) (Fig. 4 25 ). In 2011, marketable zucchini yields (kg) were not significantly different by treatment ( F = 1.32; df = 1, 14; P = 0.3092) (Fig. 4 26 ). In 2012, marketable zucchini yields (kg) were less in the buckwheat arrangement C treatment compared with

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76 buckwheat arrangement B ( F = 5.05; df = 1, 18; P = 0.0374) and the bareground treatment ( F = 7.22; df = 1, 18; P = 0.0150) (Fig. 4 27 ). In 2013, marketable squash yields (kg) were less in the mixed var ieties treatment compared with buckwheat arrangement A treatment ( F = 8.22 ; df = 1, 6 ; P = 0.0285) and buckwheat arrangement B treatment ( F = 12.70 ; df = 1, 6 ; P = 0.0119) (Fig. 4 28 ). Discussion Aphids Fewer alate aphids were collected from pan traps in the buckwheat arrangement C treatment during the 2011 cropping season but this was not observed during the 2012 season. These differences may be related to time of planting of buckwheat approximately 7 d earlier in 2011 than in 2012. Taller and more establ ished buckwheat plants could act as a barrier to aphids locating squash plants and reduce the population of alate aphids . Fewer aphids were also observed on squash plants via in situ counts in the buckwheat arrangement C treatment and buckwheat arrangement A treatments in the 2012 season. Hooks et al. (1998) and Nyoike and Liburd (2010) similarly found reduced aphid densities on squash planted with buckwheat when compared with bareground and white mulch treatments, respectively. It is hypothesized that the finding abilities and deters aphids from landing on the host plant by ( Root 1973 als o had fewer aphid s as observed by in situ counts compared with buckwheat treatments (Fig. 4 5). Although planting multiple squash cultivars has not been studied, Ninkovic et al. (2002) found that aphid acceptance in barley cultivars was significantly

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77 reduc ed when sown together with other cultivars compared with pure stands, and they suggested that plant/plant communication (i.e., volatiles) could be an important mechanism affecting aphid acceptance of a host. The findings suggest that aphid densities were r educed in treatments where buckwheat was present and where multiple varieties of squash were planted. Therefore, intercropping buckwheat with squash and incorporating multiple squash varieties could be effective strategies for suppressing aphid populations . Whiteflies In 2011, immature whitefly densities were reduced in buckwheat arrangement A treatments compared with the buckwheat arrangement C treatment. In 2012, there was a significant reduction in immature whitefly densities in the bareground treatment compared with buckwheat treatments. Similar to aphids, this finding may be related to the time of establishment for the buckwheat crop 10 d before planting squash in 2011 versus 3 d in 2012 , such that more established buckwheat plants could act to deter w hitefly colonization on squash plants . A second hypothesis is that i mmature whitefly populations could be more apparent to beneficial organisms in a less diversified cropping system (Pimentel 1961, Root 1973), and therefore natural enemies present in the b areground treatment may have been more effective at reducing whitefly populations. In 2013, fewer immature whitefl ies were recorded in the mixed variety treatment compared with buckwheat treatments, which is similar to the findings of reduced aphid densiti es in mixed squash variety plantings. This may suggest that planting multiple squash varieties could have a deterre nt effect on whitefly populations.

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78 Diseases In 2011, there was a high incidence of Cucurbit leaf crumple virus in the field, where each pl ot had over 25% of plants showing virus symptoms, and virus incidence was not significantly diff erent between treatments . The field plots were bordered by several other cucurbit crops that were planted earlier in the 2011 season, including pumpkins, waterm elon, and melon. It is hypothesized that high virus incidence was a result of infected whitefly adults immigrating into the field from the bordering cucurbit fields. SSL incidence was greater in the buckwheat arrangement C treatment . A greater number of im mature whiteflies were also recorded in the buckwheat arrangement C treatment and were presumed to be responsible for inducing silverleaf symptoms (Schuster et al. 1991). In 2012, virus incidence was reduced in all buckwheat treatments when compared with t he bareground treatment . However , SSL incidence was reduced in the bareground treatment presumably due to the lower numbers of immature whiteflies recorded in those plots during 2012 . In the on farm demonstration ( 2013 ) , virus and SSL incidence was reduced in the mixed varieties treatment, which correlates with lower aphid and whitefly densities. The findings suggest that buckwheat as a living mulch can reduce the incidence of insect transmitted viruses in zucchini squash when compared with bareground trea tments , as supported by earlier work from Hooks et al. (1998) and Nyoike et al. (2008). However, buckwheat was not as effective at reducing SSL incidence. The findings suggest that a greater incidence of SSL is related to a greater number of immature white flies. When the buckwheat was planted closer in time to the squash , as

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79 in the 2012 and 2013 seasons, buckwheat was similarly not as effective at reducing immature whitefly densities. Natural Enemies In 2011 and 2012, lacewing densities were lower in both t he bareground treatment and the buckwheat arrangement C treatment compared with buckwheat arrangement A and buckwheat arrangement B treatments . This finding suggests that buckwh eat may have attracted lacewings; however, in the buckwheat arrangement C treat ment where buckwheat was planted continuously on both sides of the squash, the buckwheat may have acted as a barrier and deterred oviposition on squash plants by lacewing adults. In 2011, lacewing densities were lower in treatments where D. catalinae was r eleased, and it is hypothesize d that intraguild predation ma y have been a factor . In addition, the findings from 2012 suggest that both Geocoris sp p . and Orius sp p . densities were higher in buckwheat treatments , which supports the hypoth esis that intercrop ping can aid in the enhancement of natural enemy populations (Bugg 1991). Ground beetle (Carabidae) densities were also higher in buckwheat treatments in 2012 compared with the bareground treatment. Prasifka et al. (2006) also reported that living mulches integrated into a corn soybean forage crop rotation positively impacted ground beetle densities and suggested that the additional ground cover provided by living mulches can serve to enhance ground beetle populations. Both Encarsia sp p . and Eretmocerus sp p . were observed to be more abundant in buckwheat arrangement A treatments and the buckwheat arrangement C treatment compared with buckwheat arrangement B treatments in 2011. With re spect to pest densities, immature whitefly densities were high in buckwhea t arrangement C , but were

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80 significantly reduced in buckwheat arrangement A. In 2012, Encarsia sp p . were more abundant in buckwheat arrangement B compared with the other treatments, where immature whitefly densities were high, but not different from other b uckwheat treatments. In contrast, Trichogramma sp p . densities were greater in the bareground treatment compared with buckwheat treatments. In treatments where buckwheat was absent, the pest or the host plant of the pest c ould have been more apparent to the parasitoid (Pimentel 1961, Root 1973) and could have facilitated greater host finding abilities, particularly of melon worm and other lepidopteran eggs that Trichogramma sp p . are known to parasitize (Hass an 1994) . Generally, natural enemy abundance varied between treatments, and we hypothesize this was likely due to differences between natural enemy species in host finding behavior and their dependence on alternative resources. The d ifferent buckwheat arrangements may have also affected host finding behavi or. In 2013, we did not observe significant differences in natural enemy densities, which may have been a result of smaller plot sizes and increased movement between plots. There were no differences among treatments with similar intercropping tactics when considering the effect of D. catalinae on pest populations, disease incidence, and zucchini yield. This finding may suggest that there is movement of D. catalinae between plots into areas where it is not released, which is supported by observations of D. c atalinae in plots where it was not released. Heinz et al. (1999) reported dispersal by D. catalinae was less than 1m/day and suggested that movement out of experimental plots should be minimal. However, Hoelmer and Pickett (2003) reported a high degree of dispersal by D. catalinae in the field, which is consistent with the observations for this

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81 study. Therefore, it was difficult to determine the effectiveness of D. catalinae on whitefly populations in the field. Future research should consider alternative m ethods to evaluating the effect of D. catalinae on whitefly populations in the field, such as the use of exclusion cages around treatment plots. Plant Measurements and Marketable Yields In all three years, the squash plants in buckwheat arrangement B were significantly smaller than the squash plants in buckwheat arrangement A. This finding suggests that competition between squash and buckwheat was greater in buckwheat arrangement B treatments than in buckwheat arrangement A treatments. Squash plants in the buckwheat arrangement C treatment were taller than buckwheat in arrangement B and the baregroun d treatment . It is hypothesize d that the presence of buckwheat on both sides of the squash plants , as in buckwheat arrangement C, forced plants to grow taller in stead of wider. It was also observed that squash plant height in the bareground treatment was reduced compared with plants in buckwheat treatments ; however plant width was greater in the bareground treatment compared with buckwheat arrangement B and buckwh eat arrangement C . It is hypothesize d that the absence of buckwheat allowed squash plant s to grow in girth ( wider ) instead of being forced to grow taller. Squash p lant size in buckwheat arrangement A was not significantly reduced compared with plants in th e bareground treatment , which suggests that competition between buckwheat and zucchini crop was minimized in buckwheat arrangement A. Overall, zucchini plants in the mixed varieties treatment in the on farm demonstration were smaller than the other treatme nts . This observation suggests that the varieties selected

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82 for the mixed varieties treatment were not as vigorous as the variety used in the buckwheat treatments. In 2011, marketable yields were not different between treatments, and it is hypothesize d that high virus incidence contributed to low yields across treatments. A second hypothesis is that by planting the buckwheat 10 d earlier than the squash, early season competition between buckwheat and squash may have been high and could have contributed to re duced yields. In 2012, marketable yields were reduced in the buckwheat arrangement C treatment compared with the other treatments. Nyoike and Liburd (2010) similarly reported high competition between buckwheat and zucchini squash for this arrangement , whic h resulted in smaller plant size and reduced yields. However, marketable yields were not different between the bareground treatment and buckwheat arrangements A and B. This finding suggests that manipulating the buckwheat spacing within the squash crop can minimize the competition between the main crop and the living mulch and improve yields . In 2013, a reduction in marketable yields in the mixed varieties treatment was noted . The reason for this may be related to the fact that the varieties the growers us ed for this treatment were not as high yielding as the other varieties utilized in the buckwheat treatments. However, observations of a significant reduction in pest densities and virus incidence in the mixed varieties treatment suggest that this could be an effective strategy if higher yielding varieties are incorporated. In conclusion, t his study should be useful in providing information on how intercropping tactics can be utilized to maximize yields in squash and other crop ping systems. An important find ing from this intercropping research was that manipulations in

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83 space and time can serve to reduce competition between the living mulch and the main crop and ultimately increase marketable yields. While marketable yields were not significantly different bet ween buckwheat arrangements A and B, squash plants were larger in buckwheat arrangement A compared with buckwheat arrangement B. Based on conversations with producers and farm managers, buckwheat arrangement A was preferred over buckwheat arrangement B in terms of planting ease and reduction in labor costs. Therefore, buckwheat arrangement A is recommended for intercropping buckwheat and squash for the purpose of reducing competition between buckwheat and squash plants and providing a more cost effective option wh en integrating buckwheat into an organic squash production system. While reduced pest and disease incidence was observed in buckwheat treatments during the three year study, observations were not consistently different compared to the bareground treatment. Hooks and Wright (2008) found adult and immature whitefly numbers to be similar among bareground and mulch treatments in zucchini squash. Based on their findings, they suggest that in areas where whitefly densities are high, as is the case during the fall growing season, buckwheat may not be a feasible barrier plant. However, when used in conjunction with other pest management tactics, enhanced pest and disease suppression could be achieved. With the added benefits of increased natural enemy densities that were observed in buckwheat and the addition of insecticides approved for organic production , a reduction in pest and disease pressure and an increase in yields could be achieved. Therefore, future research should evaluate the effectiveness of organically approved insecticides on aphid and whitefly populations and how this pest management strategy can be

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84 incorporated into an IPM program utilizing living mulches in organic squash production systems.

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85 Table 4 1. Mean ± SEM of natural enemies sample d by in si tu counts over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Means in rows followed by the same letter are not significantly different ( P 0.05). a F = 6.90; df = 4, 355; P 0.0001 b F = 0.37; df = 4, 355; P = 0.8324 c F = 0.16; df = 4, 355; P = 0.9575 d F = 4.96; df = 4, 355; P = 0.0007 e F = 1.38; df = 4, 355; P = 0.2414 Mean number of natural enemies per treatment ± SEM Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Chrysopidae a 0.69±0.1a 0.13±0.03c 0.29±0.06b 0.17±0.04c 0.2 ±0.05bc Coccinellidae b 0.05±0.03a 0.11±0.02a 0.09±0.04a 0.04±0.03a 0.08±0.03a Geocoris sp p . c 0.11±0.03a 0.09±0.05a 0.04±0.03a 0.09±0.03a 0.1±0.07a Orius sp p . d 0.15±0.04c 0.17±0.04c 0.16±0.03c 0.28±0.04b 0.46±0.06a Araneae e 0.16±0.04ab 0.17±0.03a 0.23±0 .05a 0.11±0.04ab 0.08±0.03b

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86 Table 4 2. Mean ± SEM of natural enemies sampled by in situ count s for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Means in rows followed by the same letter are not significantly differe nt ( P 0.05). a F = 3.79; df = 5, 690; P = 0.0021 b F = 8.66; df = 5, 690; P 0.0001 c F = 1.40; df = 5, 690; P = 0.2209 Mean number o f natural enemies per treatment ± SEM Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Chrysopidae a 0.6±0.14a 0.45±0.1ab 0.63±0.1a 0.67±.17a 0.22±0.06c 0.32 ±0.06bc Geocoris sp p . b 0.08±0.03cd 0.17±0.05bc 0.27±0.07ab 0.36±0.09a 0.28±0.07ab 0.03±0.01d Araneae c 0.1±0.03a 0.09±0.03ab 0.08±0.03ab 0.04±0.02b 0.12±0.03a 0.14±0.03a

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87 Table 4 3. Mean ± SEM of natural enemies collected from yellow stick traps over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Means in rows followed by the same letter are not significantly different ( P 0.05). a F = 1.29; df = 4, 165; P = 0.2753 b F = 3.23; df = 4, 165; P = 0.0140 c F = 2.05; df = 4, 165; P = 0.0894 d F = 2.80; df = 4, 165; P = 0.0279 Mean number of natural enemies per treatment ± SEM Buckwhe at alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Encarsia sp p . a 2.85±0.58a 2.95±0.6a 2.0±0.5a 2.1±0.37a 3.03±0.67a Eretmocerus sp p . b 2.25±0.56a 2.6±0.62a 0.9±0.26b 1.4±0.36ab 2.48±0.69a Orius sp p . c 1.78±0.39a 1.18±0.33ab 1.3±0.4ab 0.85±0.19b 1.4±0.33ab Trichogramma sp p . d 2.7±0.35a 2.48±0.4ab 1.77±0.34 b c 2.2±0.32abc 1.73±0.27c

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88 Table 4 4. Mean ± SEM of natural enemies collected from yellow sticky traps for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Mean number of natural enemies per treatme nt ± SEM Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Encarsia sp p . a 3.23±0.63abc 3.13±0.41bc 4.23±0.53a 3.96±0.65ab 2.5±0.42c 2.75±0.45c Eretmocerus s p p . b 0.06±0.04b 0.23±0.07ab 0.13±0.05ab 0.17±0.07ab 0.13±0.06ab 0.27±0.09a Orius sp p . c 0.23±0.06ab 0.1±0.05ab 0.27±0.14a 0.21±0.07ab 0.17±0.06ab 0.04±0.03b Trichogramma sp p . d 4.65±0.48b 4.48±0.42b 3.98±0.54b 4.17±0.47b 4.25±0.43b 8.54±0.89a Means in row s followed by the same letter are not significantly different ( P 0.05). a F = 3.74; df = 5, 252; P = 0.0028 b F = 1.34; df = 5, 252; P = 0.2491 c F = 1.53; df = 5, 252; P = 0.1809 d F = 11.31; df = 5, 252; P 0.0001

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89 Table 4 5. Mean ± SEM of natural enemies collected from pitfall traps for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both si des, and bareground. Mean number of natural enemies per treatment ± SEM Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Carabidae a 0.65±0.11a 0.6±0.14a 0. 53±0.12a 0.5±0.15a 0.55±0.14a 0.13±0.06b Araneae b 0.53±0.18ab 0.28±0.11ab 0.3±0.11ab 0.25±0.11b 0.53±0.17ab 0.63±0.22a Means in rows followed by the same letter are not significantly different ( P 0.05). a F = 3.18; df = 5, 210; P = 0.0087 b F = 1.06; df = 5, 210; P = 0.3828

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90 Figure 4 1. Diagrams of the different buckwheat arrangements implemented in the intercropping field study. A) Buckwheat arrangement A where buckwheat is alternating on either side of the squash, B) buckwheat arran gement B where buckwheat is planted in the middle of the squash, and C) buckwheat arrangement C where buckwheat is planted continuously on both sides of the squash.

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91 Figure 4 2 . Mean ( ± SE) number of aphids sampled per squash lea f by in situ counts over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both si des. Treatments with the same letter are not significantly different ( P 0 1 2 3 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average # of aphids/leaf

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92 Figure 4 3 . Mean ( ± SE) number of alate aphids s ampled per pan trap over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly different ( P 0.05). 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Buckwheat alternating Buckwheat alteranting with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average # of alate aphids/pan trap a c ab c bc

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93 Figure 4 4 . Mean ( ± SE) number of aphids sampled per squa sh lea f by in situ counts over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwhe at on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0.0 0.5 1.0 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average # of aphids/leaf c ab ab ab bc a

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94 Figure 4 5 . Mean ( ± SE) number of alate aphids s ampled per pan trap over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , b uckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0.0 0.1 0.2 0.3 0.4 0.5 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average # of alate aphids/pan trap

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95 Figure 4 6 . Mean ( ± SE) number of aphids sampled per squash lea f by in situ counts over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same letter are not significantly different ( P 0.05). 0 1 2 3 4 5 6 7 Buckwheat alternating Buckwheat middle Mixed Varieties Average # of aphids/leaf b a a

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96 Figure 4 7 . Mean ( ± SE) number of alate aphids s ampled per pan trap over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same letter are not significantly different ( P 0 0.2 0.4 0.6 0.8 Buckwheat alternating Buckwheat middle Mixed Varieties Average # of alate aphids/pan trap

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97 Figure 4 8 . Mean ( ± SE) number of immature whiteflies sampled from 3.14 cm 2 leaf discs over a five week period for the intercropping field stu dy in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly diff erent ( P 0 5 10 15 20 25 30 35 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average # of immature whiteflies/leaf disc ab ab a b b

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98 Figure 4 9 . Mean ( ± SE) number of adult whiteflies sampled from yellow sticky traps (YST) over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat altern ating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly different ( P 0 5 10 15 20 25 30 35 40 45 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average # of adult whiteflies/YST

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99 Figure 4 10 . Mean ( ± SE) number of immature whitefl ies sampled from 3.14 cm 2 leaf discs over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalin ae , buckwheat on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0 5 10 15 20 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average # of immature whiteflies/leaf disc b a a a a a

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100 Figure 4 11 . Mean ( ± SE) number of adult whiteflies sampled from yellow sticky traps (YST) over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternat ing with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0 10 20 30 40 50 60 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average # of adult Whiteflies/YST

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101 Figure 4 12 . Mean ( ± SE ) number of immature whiteflies sampled from 3.14 cm 2 leaf discs over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same lett er are not significantly different ( P 0.05). 0 1 2 3 4 5 6 7 8 Buckwheat alternating Buckwheat middle Mixed Varieties Average # of immature whiteflies/leaf disc b a a

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102 Figure 4 13 . Mean ( ± SE) number of adult whiteflies sampled from yellow sticky traps (YST) over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same letter are not significantly different ( P 0.05). 0 5 10 15 20 25 Buckwheat alternating Buckwheat middle Mixed Varieties Average # of adult whiteflies/YST

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103 Figure 4 14 . Mean ( ± SE) number of squash plants with virus symptoms over a five week period for the intercropping fiel d study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly different ( P 0.05). 0 5 10 15 20 25 30 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average # of plants with virus symptoms

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104 Figure 4 15 . Mean ( ± SE) squash silverleaf (SSL) disorder symptom rati ng per squash plant over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat altern ating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly different ( P 0 1 2 3 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average SSL symptom rating/ squash plant a b b b b

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105 Figure 4 16 . Mean ( ± SE) number o f squash plants with virus symptoms over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalina e , buckwheat on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0 1 2 3 4 5 6 7 8 9 10 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average # of squash plants with virus symptoms c c b b b a

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106 Figure 4 17 . Mean ( ± SE) squash silverleaf (SSL) disorder symptom rati ng per squash plant over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0 1 2 3 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average SSL symptom rating/ squash plant c ab ab a a b

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107 Figure 4 18 . Mean ( ± SE) number of squash plants with virus symptoms over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same letter are not significantly dif ferent ( P 0 2 4 6 8 10 12 14 16 18 Buckwheat alternating Buckwheat middle Mixed Varieties Average # of squash plants with virus symptoms b b a

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108 Figure 4 19 . Mean ( ± SE) squash silverleaf (SSL) disorder symptom rati ng per squash plant over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same letter are not significantly different ( P 0.05). 0 1 2 3 Buckwheat alternating Buckwheat middle Mixed Varieties Average SSL symptom rating/squash plant c a b

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109 Figure 4 20 . Mean ( ± SE) height (cm) of sq uash plants sampled over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly differe nt ( P 0 5 10 15 20 25 30 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average height (cm) of squash plant a b b a a

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110 Figure 4 21 . Mean ( ± SE) width (cm) of squash plants samp led over a five week period for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buck wheat in the middle, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly different ( P 0 10 20 30 40 50 60 70 80 90 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Average width (cm) of squash plant b b a a a

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111 Figure 4 22 . Mean ( ± SE) height (cm) of sq uash plants sampled over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bare ground. Treatments with the same letter are not significantly different ( P 0 5 10 15 20 25 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average height (cm) of squash plant c a b b ab b

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112 Figure 4 23 . Mean ( ± SE) width (cm) of sq uash plants sampled over a five week period for the intercropping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckw heat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Treatments with the same letter are not significantly different ( P 0 20 40 60 80 100 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Average width (cm) of squash plant a c b b a b

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113 Figure 4 24 . Mean ( ± SE) height (cm) of squash plants s ampled over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with the same letter are not significantly different ( P 0 5 10 15 20 25 30 Buckwheat alternating Buckwheat middle Mixed Varieties Average height (cm) of squash plant b a a

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114 Figure 4 25 . Mean ( ± SE) width (cm) of sq uash plants sampled over a five week period for the intercropping field study in fall 2013 for three treatments: buckwheat alternating, buckwheat in the middle, and mixed varieties. Treatments with t he same letter are not significantly different ( P 0 20 40 60 80 100 120 Buckwheat alternating Buckwheat middle Mixed Varieties Average width (cm) of squash plant c b a

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115 Figure 4 26 . Total marketable squash yield (kg) ( ± SE) harvested for the intercropping field study in fall 2011 for five treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middl e, buckwheat in the middle with D. catalinae , and buckwheat on both sides. Treatments with the same letter are not significantly different ( P 0 0.5 1 1.5 2 2.5 3 3.5 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Total Marketable Yield (kg)

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116 Figure 4 27 . Total marketable squash yield (kg) ( ± SE) harvested for the intercrop ping field study in fall 2012 for six treatments: buckwheat alternating, buckwheat alternating with D. catalinae , buckwheat in the middle, buckwheat in the middle with D. catalinae , buckwheat on both sides, and bareground. Treatments with the same letter a re not significantly different ( P 0 2 4 6 8 10 12 14 Buckwheat alternating Buckwheat alternating with D. catalinae Buckwheat middle Buckwheat middle with D. catalinae Buckwheat both sides Bareground Total Marketable Yield (kg) a c ab bc ab ab

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117 Figure 4 28 . Total marketable squash yield (kg) ( ± SE) harvested for the intercropping field study in fall 2013 for three treatments: buckwheat altern ating, buckwheat in the middle, and mixed varieties. Treatments with the sam e letter are not significantly different ( P 0 2 4 6 8 10 Buckwheat alternating Buckwheat middle Mixed Varieties Total Marketable Yield (kg) b a a

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118 CHAPTER 5 EVALUATION OF ORGANICALLY APPROVED INSECTICIDES FOR CONTROL OF SILVERLEAF WHITEFLY IN ORGANIC SQUASH In 2012, Florida was ranked first as the top producer of squash in the United States ( FDACS 2013). Although the vast majority of the squash produced in Florida are grown conventionally, about 20 25 % of squash production implements USDA organic standards ( Liburd 2012 ). Regardless of the squash production system (conventional vs. orga nic), damage due to pest infestations is a major problem for squash growers around the state. A significant pest of zucchini squash , Cucurbita pepo L. in Florida is the silverleaf whitefly, Bemisia tabaci (Gennadius) B bio type (Nyoike and Liburd 2010). Thi s pest is largely responsible for transmitting viruses, including Cucurbit leaf crumple virus , which can result in stunted plants, deformed fruit, and significantly reduce d yields . The silverleaf whitefly is also responsible for causing physiological disor ders in squash, primarily squash silverleaf disorder (SSL) associated with the feeding of immature whiteflies (Yokomi et al. 1990) . SSL can reduce the photosynthetic ability of leaves (Cardoza et al. 2000, McAuslane et al. 2004 ), and i n severe cases with h eavy infestations, the plant may be stunted, reducing fruit production and causing severe economic damage to growers ( Costa et al. 1994 ). Conventio nal cucurbit growers use soil applications of imidacloprid [Admire®Pro (Bayer Cropscience , Research Triangle Park, NC )] to manage silverleaf whitefly populations (Seal 2008), which is a neonicotinoid insecticide that is systemic in plants and can be applied to t he soil (Palumbo et al. 2001). For organic growers, insecticides are used as a last resort after preve ntative and cultural tactics have been explored. These insecticides must meet USDA organic standards and are normally listed on the Organic Materials Review Institu te (OMRI) data base . Insecticides approved for control

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119 of whiteflies in organic squash produ ction include insec ticidal soaps (i.e., M Pede® , Dow AgroSciences LLC, Indianapolis, IN ), p yrethrin (i.e PyGanic® , McLaughlin Gormley King Company, Minneapolis, MN ), and a zadirachtin (i.e., AzaSol®, Aza Direct® , Arborjet Inc. , Woburn , MA ) (Dayan et al. 2009 ). Spinosad (i.e., Entrust® , Dow AgroSciences LLC, Indianapolis, IN ) is also commonly used in organic vegetable production; however, it is not specifically recommended for control of whiteflies (Dayan et al. 2009). Since whitefly adults are continually co lonizing fields and moving between plants, frequent applications of foliar sprays may be required to prevent B. tabaci population buildup and to reduce the spread of plant viruses transmitted by whiteflies (Palumbo et al. 2001). However, insecticides can a id in preventing pest population build up on the host and reducing the proliferation of viruses and transmission among plants (Nyoike and Liburd 2010). It will be important to incorporate insecticides with integrated pest management (IPM) strategies in ord er to delay the development of resista nce in pest populations, reduce the spread of disease among and between fields, and conserve natural enemies. The coccinellid beetle Delphastus catalinae ( Horn ) (Coleoptera: Coccinellidae) is an obligate predator of the silverleaf whitefly and has bee n cited as a good biological control candidate for whiteflies as a result of high prey consumption rates, long adult lives, and high fecundity rates (Heinz et al. 1999). Heinz et al. (1999) reporte d in exclusion cage experiments that D. catalinae reduced silverleaf whitefly densities by 55% to 67%. Legaspi et al. (2006) observed that D. catalinae displayed a preference for

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120 the silverleaf whitefly in the egg stage, followed by small then large nymphs. Therefore, D. catalinae are likely to be effective early in the season when eggs are abundant. Management of whiteflies in squash is extremely difficult irrespective of the production system (organic or conventional) that growers are using. However, organic growers face an even mor e daunting task, because the m ajority of pest management practices are developed for conventional growers and often are not permitted in organic production (i.e., synthetic pesticides and fertilizers). Therefore, a lack of knowledge on the effectiveness of organically labelled pesticid es that are approved for organic production is one of the constraints to organic squash production in Florida. Resear ch on the effectiveness of organically approved insecticides for managing whitefly populations in squash as well as their effects on natura l enemies will provide additional information on how these insecticides can be used to regulate pest populations. The purpose of this study was to evaluate several organically labelled pesticides for the control of silverleaf whitefly in organic squash an d to investigate the effects of selected pesticides on a key natural enemy, D . catalinae that is used to control whiteflies. The specific objectives of this study were : 1) to assess the effectiveness of organically approved insecticides on whitefly populat ions i n zucchini squash and 2) to determine the effect of these insecticides on mortality and feeding behavior of D. catalinae . Materials and Methods Research was conducted in the s pring of 2013 and 2014 in the Small Fruit and Vegetable IPM greenhouse at the University of Florida in Gainesville. One liter pots were sown with the zucchini

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121 Winslow, ME) . Plants were grown from seeds using Miracle Gro Organic garden soil (Miracle Gro, Marysville, OH) and squash p lants were fertilized with organic fertilizer (Scotts Organic Fertilizer, Marysville, OH) . Adult whiteflies and D. catalinae were obtained from a colony reared in 30 X 30 cm wire mesh cages on collards in the Small Fruit and Vegetable IPM laboratory. Delph astus catalinae adults were originally purchased from Bicontrol Network, LLC (Brentwood, TN) and maintained on a colony of silverleaf whiteflies. Cages were kept in an environmental chamber at 25°C wi th 60% RH on L:D 14 :10 in the Department of Entomology a nd Nematology, Univers ity of Florida, Gainesville, FL . Plants we re watered 2 3 times per week to maintain turgidity and new plants were put into the cage once every 2 w . Assessing the effectiveness of organically approved insecticides on whitefly po pulations. This experiment compared the effectiveness of four insecticides approved for organic production and an untreated cont rol on whitefly densities. Organically approved treatments were applied with a backpack sprayer at the tes and included : 1) Aza Sol® at 0.42 kg in 467.9 L of water/ ha ( Arborjet Inc. , Woburn , MA ), 2) PyGanic® EC 1.4 at 4.67 L/ha (McLaughlin Gormley King Company, Minneapolis, MN), 3) M Pede® at 20.05 ml per L of water (Dow AgroSciences LLC, Indianapolis, IN), 4) Entrust® SC at 0.59 L/ha (Dow AgroSciences LLC, Indianapolis, IN), and 5) an untreated control. Each treatment was applied to squash plants contained in a 1 m 3 exclusion cage with 5 replicates. Twenty five silverleaf whitefly adults were released into e ach cage and given 2 w to establish on the squash plants before the insecticide applications. Sampling was conducted every 2 d for

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122 3 w using the leaf turn method , such that the undersides of all leaves were examined for immature and adult whiteflies. Effects of organic insecticides on Delphastus catalinae . The best performing insecticides from the whitefly efficacy study in experiment 1 were used in a second experiment to determine their effects on D. catalinae . Experimental desig n was a 3 x 4 factorial with factor A (insecticides) and B (predator). Insecticides were applied at labeled rates and treatments included : 1) PyGanic® EC 1.4, 2) M Pede®, and 3) untreated control. Predator treatments included 1) releasing D. catalinae 1 d post insecticide treatment; 2) releasing D. catalinae 3 d post insecticide treatment; 3) releasing D. catalinae 5 d post insecticide treatment and 4) no release of D. catalinae (control). Each treatment was applied to four squash plants contained in a 1 m 3 exclusion cage . Twenty five silverleaf whitefly adults were released into each cage and given 2 w to establish and reproduce on the squash plants before the insecticide applications to provide food for the predators . In treatments containin g D. catalinae , five D. catalinae adults were released into each cage to achieve a predator to prey ratio of 1:5. Sampling was conducted every 2 d for 2 w using the leaf turn method to evaluate D. catalinae mortality, as well as immature and adult whitefly populations. Data Analysis. Data were analyzed using repeated measures analysis of variance procedure ( ANOVA; PROC GLM, SAS Institute 2009) to investigate insect population density over time. Sample date was the repeated measure and t reatment means were separated by least significant differences (LSD) test (SAS Institute 2009). Differences among treatments were considered significant if P

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123 Results Effectiveness of Organically Approved Insecticides on Whiteflies in Organic Squa sh In 2013, adult whitefly densities were different by treatment ( F = 4.55; df = 4, 180; P = 0.0016) and over time ( F = 3.26; df = 8, 180; P = 0.0017), but there was no interaction effect ( F = 1.14; df = 32, 180; P = 0.2880). Adult whitefly densities were less in PyGanic®, M Pede®, and Aza Sol® treatments compared with Entrust® and the untreated control (Fig. 5 1). Immature whitefly densities were different by treatment ( F = 3.77; df = 4, 180; P = 0.0057) and over time ( F = 94.95; df = 8, 180; P there was no interaction effect ( F = 1.09; df = 32, 180; P = 0.3515). There were fewer immature whiteflies in the M Pede® treatment compared with the untreated control (Fig. 5 2). In 2014, adult whitefly densities were different by treatme nt ( F = 24.15; df = 4, 220; P F = 12.99; df = 10, 220; P interaction effect ( F = 1.24; df = 40, 220; P = 0.1660). Adult whitefly densities were less in PyGanic®, M Pede®, and Aza Sol® treatments compared with the untreated control (Fig. 5 3). Adult whitefly densities were also less in PyGanic® and M Pede® treatments compared with AzaSol® and Entrust® treatment s (Fig. 5 3). Immature whitefly densities were different by treatment ( F = 14.88 ; df = 4, 220; P F = 276.78 ; df = 10, 220; P n interaction effect ( F = 3.03 ; df = 40, 220; P

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124 application. Immature whitefly densities were less i n the M Pede® treatment compared with Entrust® and the untreated control (Fig. 5 4). Effects of Selected Insecticides on Delphastus catalinae In 2013, D. catalinae densities were marginally different by insecticide treatment ( F = 2.87; df = 2, 63; P = 0. 0639), but not by release time ( F = 1.95; df = 2, 63; P = 0.1511) and there was no interaction effect ( F = 0.27; df = 4, 63; P = 0 .8942). Delphastus catalinae populations were reduced in both PyGanic® and M Pede® treatments when rel eased 1 d after insect icide application compared with the untreated control (Fig. 5 5). In 2014, D. catalinae densities were different by insecticide treatment ( F = 5.30; df = 2, 99; P = 0.0065) and marginally different by release time ( F = 2.69; df = 2, 99; P = 0.0729), but th ere was no interaction effect ( F = 0.22; df = 2, 99; P = 0.9242). Delphastus catalinae populations were reduced in both PyGanic® and M P ede® treatments when released 1 d after insecticide application compared with the untreated control (Fig. 5 6). Delpha stus catalinae populations were also reduced in PyGanic® and M P ede® treatments when released 1 d after insecticide application compared with D. catalinae adults released 5 d after insecticide application (Fig. 5 6). In 2013, adult whitefly densities we re different by insecticide treatment ( F = 15.80 ; df = 2, 2 04 ; P there was no significant release time ( F = 0.3 4 ; df = 3, 2 04 ; P = 0.79 52 ) or interaction effect ( F = 0.25 ; df = 6, 2 04 ; P = 0.95 99 ). Adult whitefly densities were reduced in the PyGanic® and M Pede® treatments compared with the untreated c ontrol (Fig. 5 7). However, there was no significant difference in adult whitefly populations based on D. catalinae releases (Fig. 5 7). A dult whitefly densities were also different over time ( F = 12.94 ; df = 4 , 2 04 ; P and there

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125 was a significant insecticide treatment × time interaction ( F = 1.95 ; df = 8 , 2 04 ; P = 0. 0545 ) , such that treatment differences were observed after insecticide application. However, there was no release time × time interaction effect ( F = 0.13 ; df = 12 , 2 04 ; P = 0. 9999 ). I n 2013, i mmature whitefly densities were different by insecticide treatment ( F = 4.49 ; df = 2, 2 04 ; P = 0.01 24 ), but not by release time ( F = 2. 07 ; df = 3, 2 04 ; P = 0.10 59 ) . However, there was an interaction effect ( F = 7. 68 ; df = 6, 2 04 ; P There were fewer immature whiteflies in the PyGanic® treatment compared with the M Pede® treatment and the untreated control (Fig. 5 8). In the PyGanic® treatment, immature whitefly populations were reduced when D. catalinae was released 3 d and 5 d after insecticide application when compared with D. catalinae adults released 1 d after insecticide application (Fig. 5 8). Immature whitefly densities in the M Pede® treatment were reduced when D. catalinae adults were released 1 d after i nsecticide application and when D. catalinae was not released compared with the other release times (Fig. 5 8). Immature whitefly densities in the untreated control were reduced when D. catalinae adults were released 1 d after insecticide application com pared with the other release times (Fig. 5 8). Immature whitefly densities were also different over time ( F = 42.19 ; df = 4 , 2 04 ; P but there was no insecticide treatment × time interaction effect ( F = 1.42 ; df = 8 , 2 04 ; P = 0. 1883 ) or release t ime × time interaction effect ( F = 0.45 ; df = 12 , 2 04 ; P = 0. 9419 ). In 2014, adult whitefly densities were different by insecticide treatment ( F = 54.78 ; df = 2, 288 ; P there was no significant release time ( F = 1.05 ; df = 3, 288 ; P = 0.3693 ) or interaction effect ( F = 0.50; df = 6, 288 ; P = 0.80 49 ). Adult

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126 whitefly densities were reduced in the PyGanic® and M Pede® treatments compared with the untreated control, but there was no significant difference in adult whitefly populations based on D. catalinae releases (Fig. 5 9). A dult whitefly densities were also different over time ( F = 65.48 ; df = 6 , 2 88 ; P and there was a n insecticide treatment × time interaction ( F = 5.88 ; df = 12 , 2 88 ; P ) , such that treatment differences were observed after insecticide application. However, there was no release time × time interaction effect ( F = 0.09 ; df = 18 , 2 88 ; P = 1.0000 ) . In 2014, i mmature whitefly densities were different by insecticide treatment ( F = 31.89 ; df = 2, 288 ; P F = 15.81 ; df = 3, 288 ; P there was a n interaction effect ( F = 8.54 ; df = 6, 288 ; P immature whiteflies in the PyGanic® treatment compared with the M Pede® treatment and the untreated control (Fig. 5 10). In the PyGanic® treatment, immature whitefly populations were reduced when D. catalinae was released 3 d after insecticide application when compared with the other release times (Fig. 5 10). Immature whitefly densities in the M Pede® treatment were reduced when D. catalinae was released 5 d after insecticide application when compared with the other relea se times (Fig. 5 10). Immature whitefly densities in the untreated control were reduced when D. catalinae adults were released compared with when D. catalinae adults were not released (Fig. 5 10). Immature whitefly densities were also different over time ( F = 98.22 ; df = 6 , 2 88 ; P and there was a n insecticide treatment × time interaction ( F = 5.40 ; df = 12 , 2 88 ; P ) , such that treatment differences were observed after insecticide application. There was also a release time × time interacti on ( F = 5.03 ; df = 1 8 , 2 88 ; P

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127 0.0001 ) , such that treatment differences were observed five days after D. catalinae had been released . Discussion Effectiveness of Organically Approved Insecticides on Whiteflies in Organic Squash PyGanic®, M Pede®, and Aza Sol® were effective in reducing adult whitefly populations on squash when compared with the untreated control. Entrust® did not reduce adult whitefly populations compared with the untreated control. Organic growers frequently use Entrust® for whitefly con trol due to limited organic tools for whitefly management. Entrust® has been shown to be effective against other pests including Fadamiro 200 6, Padilla Cubas et al. 2006). However, it has been ineffective against whiteflies in this study. Entrust® is a n aturalyte insecticide from the Spinosad group and is formulated from the fermentation of the natural bacterium, Saccharopolyspora spinosa (Dow Chemical Company 2001). The mode of action is by contact and ingestion , which induces excitation of neurons in th e central nervous system and produces involuntary muscle contractions and tremors (Dayan et al. 2009) . Therefore, Entrust® has little effect on sucking homopteran insects such as the silverleaf whitefly , which resulted in its ineffectiveness to suppress wh iteflies. M Pede® was the only insecticide that significantly reduced immature whitefly populations on squash compared with the untreated control. This finding has significant implications for the control of immature whiteflies and the incidence of physio logical disorders in squash, since immature whiteflies have been implicated in the spread of

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128 squash silverleaf disorder. Liu and Stansly (2000) also found M Pede to be effective at reducing immature populations of B. tabaci on tomatoes ; however a higher co ncentration is necessary (i.e., 20 ml/L) to achieve the same level of reduction in immature whitefly population s when compared to other products used in conventional systems . Effects of Selected Insecticides on Delphastus catalinae The findings from thi s experiment suggest that D . catalinae adult densitie s were reduced in PyGanic® and M Pede® treatments. In 2014, D. catalinae adult densities were reduced 1 d post insecticide application for both PyGanic® and M Pede® treatments compared with 5 d post application . Although a similar trend was observed in 2013, D. catalinae densities were not statistically different by release times, which may be a result of the low numbers of D. catalinae that were released. The findings suggests there may be a need to delay (approximately 3 5 d) the release of D. catalinae when used in conjunction with PyGanic® or M Pede® for efficient pest management. Adult whiteflies were not affected by the presence of D. catalinae , which is consistent with observations that the predatory beetle does not feed on the adult stages of the silverleaf whitefly. However, adult populations were reduced by the PyGanic® and M Pede® applications, which is consistent with the findings from the first study . Immature whiteflies densities were significantly reduced in PyGanic® treatments compared with M Pede® and the untreated control. In 2013, immature whiteflies were significantly reduced when D. catalinae releases were delayed (3 5 d ) in the PyGanic® treatment ; while in 2014, immature whit eflies were reduced again when D. catalinae was released 3 d post insecticide application. These observations suggest that delaying

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129 D. catalinae adult releases after insecticide application allows for the most efficient control of whiteflies . In the un treated control with no insecticide application , a significant reduction in immature whitefly densities was observed when D. catalinae was released 1 d after treatment and at all release times for 2013 and 2014, respectively. This finding suggests that D. catalinae was effective at reducing immature whitefly densities, and is likely to be most effective at reducing whitefly populations early in the season if insecticides are not used . In the M Pede® treatment , results were variable across years and rele ase times. In 2013, significant reductions were recorded when D. catalinae was released 1 d after insecticide application; while in 2014, imm ature whiteflies were reduced 5 d post insecticide application. The observation of higher immature whitefly po pulation s when delaying D. catalinae releases (3 5 d) was unexpected , as more adults were present when releases were delayed. One hypothesis is that there may be a property of M Pede® (i.e., insecticidal soap) that may deter D. catalinae feeding activity and could explain the variation in feeding behavior . S everal D. catalinae adults were also observed in the flowers of the squash treated with M Pede®, suggesting that adults were seeking out other food sources despite the availability of immature whitefly populations. Liu and Stansly (1999) observed that some D. catalinae larvae fed on honeydew and dew drops. Therefore, it is possible that D. catalinae could utilize alternate food sources in unfavorable conditions. In addition to the possibility that M Pe de may inhibit D. catalinae feeding, another factor that could be contributing to higher immature whitefly populations in some M -

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130 Pede® treatments is the effect of insecticides on whitefly eggs, which is a life stage that was not considered in this study. L iu and Stansly (1995) reported that M Pede was not effective at reducing whitefly eggs in tomatoes compared with other insecticides used in the study, including mineral oil and a pyrethroid, bifenthrin. Therefore, if eclosion of nymphs from the egg stage w as delayed until after the insecticide was applied, a greater density of nymphs may have survived. In conclusion, M Pede® and PyGanic® were effective in reducing adult whitefly populations. M Pede® was also effective at reducing immature whitefly populati ons, but it is hypothesized that M Pede® may have a property in the insecticidal soap that is interfering with the feeding of D. catalinae . Delphastus catalinae populations were reduced when released 1 d post insecticide application. Therefore, it is rec ommended that D. catalinae should not be released within one day of spraying M Pede® and PyGanic® insecticides for maximum whitefly control. Based on these findings, the application of PyGanic® with a delayed release (3 5 d) of D. catalinae to reduce both adult and immature whitefly populations is recommended . However, further research needs to be conducted to evaluate additional insecticides approved for organic production not included in this study. For example, future studies should consider the effect o f NOFLY® WP (Natural Industries Inc., Spring, TX) , which is a microbial formulation based from the naturally occurring fungus Isaria (= Paecilomyces ) fumosoroseus and has been shown to be effective against whiteflies and other insects (Padilla Cubas et al. 2006). Additionally, a cost benefit analysis should be considered when comparing the use of different organically approved insecticides (i.e., cost of the product, residual activity, number of applications, effect on biological controls). Th e

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131 current stud y will be important for providing information on how insecticides can be used in combination with natural enemies to regulate pest popu lations in organic crop systems, especially since some of the materials used were effective against adult whiteflies, whi le the predator was effective against immature whiteflies.

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132 Figure 5 1. Mean ( ± SE) number of adult whiteflies observed per squash plant for the organically approved insecticide efficacy study in spring 2013 to determine the effectiveness of five insecti cide treatments: PyGanic®, M Pede®, AzaSol®, Entrust® , and an untreated control. Treatments with the same letter 0 1 2 3 4 5 PyGanic M-Pede AzaSol Entrust Untreated Average # of adult whiteflies/plant a a b b b

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133 Figure 5 2. Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved insecticide efficacy study in spring 2013 to determine the effe ctiveness of five insecticide treatments: PyGanic®, M Pede®, AzaSol®, Entrust®, and an untreated control. Treatments with the same letter are not significantly different ( P 0 20 40 60 80 100 120 140 PyGanic M-Pede AzaSol Entrust Untreated Average # of immature whiteflies/plant a ab ab b ab

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134 Figure 5 3. Mean ( ± SE) number of adult whitefli es observed per squash plant for the organically approved insecticide efficacy study in spring 2014 to determine the effectiveness of five insecticide treatments: PyGanic®, M Pede®, AzaSol®, Entrust®, and an untreated control. Treatments with the same lett er are not significantly different ( P 0 1 2 3 4 5 PyGanic M-Pede AzaSol Entrust Untreated Average # of adult whiteflies/plant a ab b c c

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135 Figure 5 4. Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved insecticide efficacy study in spring 2014 to determine the effectiveness of five insecticide treatments: PyGani c®, M Pede®, AzaSol®, Entrust®, and an untreated control. Treatments with the same letter are not significantly different ( P 0 20 40 60 80 100 120 PyGanic M-Pede AzaSol Entrust Untreated Average # of immature whiteflies/plant a a ab b ab

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136 Figure 5 5. Mean ( ± SE) number of D. catalinae adults observed per squash plant for the organic ally approved insecticide efficacy study evaluating the release of D. catalinae in spring 2013 to determine the impact of three insecticide treatments (PyGanic, M Pede, and an untreated control) when D. catalinae is released 1 day, 3 days, and 5 days post insecticide application. Treatments wit h the same letter are not significantly different ( P 0 0.5 1 1.5 2 1-Day 3-Day 5-Day 1-Day 3-Day 5-Day 1-Day 3-Day 5-Day Pyganic M-Pede Untreated Average # of D. catalinae /plant b ab ab b ab a a a a

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137 Figure 5 6. Mean ( ± SE) number of D. catalinae adults observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2014 to determine the impact of three insecticide treatments (PyGanic, M Ped e, and an untreated control) when D. catalinae is released 1 day, 3 days, and 5 days post insecticide application. Treatments with the same letter are not significantly different ( P 0 0.5 1 1.5 2 1-Day 3-Day 5-Day 1-Day 3-Day 5-Day 1-Day 3-Day 5-Day Pyganic M-Pede Untreated Average # of D. catalinae /plant a a a a ab b a b ab

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138 Figure 5 7. Mean ( ± SE) number of adult w hiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2013 to determine the impact of three insecticide treatments (PyGanic, M Pede, and an untreated control) when D. catalinae is released 1 day, 3 days, and 5 days post insecticide application. Treatments with the same letter are not significantly different ( P 0 1 2 3 4 5 6 7 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release Pyganic M-Pede Untreated Average # of adult whiteflies/plant ab ab ab a bc c bc c c c c c

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139 Figure 5 8. Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2013 to determine the impact of three insecticide treatments (PyGanic, M Ped e, and an untreated control) when D. catalinae is released 1 day, 3 days, and 5 days post insecticide application. Treatments with the same letter are not significantly different ( P 0 20 40 60 80 100 120 140 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release Pyganic M-Pede Untreated Average # of immature whiteflies/plant ab ab ab de cd ab a cd bc de e ab

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140 Figure 5 9. Mean ( ± SE) number of adult w hiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2014 to determine the impact of three insecticide treatments (PyGanic, M Pede, and an untreated control) when D. catalinae is released 1 day, 3 days, and 5 days post insecticide application. Treatments with the same letter are not significantly different ( P 0 1 2 3 4 5 6 7 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release Pyganic M-Pede Untreated Average # of adult whiteflies/plant b b b b b b b b a a a a

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141 Figure 5 10. Mean ( ± SE) number of immature whiteflies observed per squash plant for the organically approved insecticide efficacy study evaluating the release of D. catalinae in spring 2014 to determine the impact of three insecticide treatments (PyGanic, M Pe de, and an untreated control) when D. catalinae is released 1 day, 3 days, and 5 days post insecticide application. Treatments with the same letter are not significantly different ( P 0 50 100 150 200 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release 1-Day 3-Day 5-Day No Release Pyganic M-Pede Untreated Average # of immature whiteflies/plant a c c c ab c ab b c c d c

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142 CHAPTER 6 CONCLUSION In the greenhouse study evalua ting the preference of the silverleaf whitefly , Bemisia tabaci (Gennadius) B biotype on buckwheat and squash and the effect of Delphastus catalinae (Horn) on whitefly popula tions , whitefly densities were greater on zucchini squash whe n compared with buckwh eat. The finding suggests that buckwheat is not an attractive host for silverleaf whiteflies and could serve as an important living mulch in cucurbit production systems. T he introduction of D. catalinae on zucchini squash reduced whitefly populations, whi ch supports observations of high prey consumption rates by D. catalinae on immature silverleaf whiteflies as reported by Heinz et al. (1999) . Therefore , D. catalinae when used in conjunction with buckwheat as a living mulch could aid in the reduction of wh iteflies on zucchini squash and the incidence of whitefly transmitted diseases. The field study that was designed to select the best tactic for intercropping buckwheat, Fagopyrum esculentum demonstrated that aphid densities were reduced in buckwheat treatm ents compared with the bareg round treatment . Additionally, fewer alate aphids were collected from the buckwheat arrangement C treatment where buckwheat was grown on both sides of squash during the 2011 cropping season compared with the 2012 season. These d ifferences may be related to time of planting of buckwheat approximately 7 d earlier in 2011 than in 2012, such that taller buckwheat plants could act as a barrier to aphids locating squash plants. Therefore, buckwheat could be an important living mulch in squash cropping systems for suppressing aphid pest densities.

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143 I mmature whitefly densities were reduced in buckwheat arrangement A treatments with buckwheat alternating on either side of the squash compared with the buckwheat arrangement C treatment with buckwheat planted on both sides of the squash during the 2011 cropping system; however in 2012, less immature whiteflies were observed in the bareground treatment compared with the buckwheat treatments. It is hypothesized that greater apparency of the pest to natural enemies may have contributed to greater reduction in whitefly densities in the bareground treatment. An additional hypothesis is that, similar to aphids, this finding may be related to the time of establishment for the buckwheat crop 10 d befor e planting squash in 2011 versus 3 d in 2012, such that more established buckwheat plants could act to deter whitefly colonization on squash plants. The findings on virus incidence suggest that b uckwheat as a living mulch can help to reduce the incidence o f insect transmitted viruses in zucchini squash, as supported by similar findings from Hooks et al. (1998) and Nyoike et al. (2008). However, the effectiveness of buckwheat on SSL incidence was not clear as high rates of SSL incidence were related to high densities of immature whiteflies . Natural enemies, including b ig eyed bugs, minute pirate bugs, and carabid beetles were more abundant in buckwheat treatments compared with bareground treatments , which supports the hypothesis that intercropping can aid in the enhancement of natural enemy populations (Bugg 1991). L acewing densities were more abundant in buckwheat arrangement A, with buckwheat alternating on either side of the squash, and buckwheat arrangement B, with buckwheat planted in the middle of squas h compared with both the bareground treatment and the buckwheat arrangement C treatment with buckwheat planted on both sides of the squash. This finding suggests

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144 that buckwheat may have attracted lacewings; but the arrangement of buckwheat on both sides of the squash may have acted as a barrier for lacewing adults reaching squash plants. Generally, parasitoid densities varied between treatments, and it is hypothesize d that there were differences between natural enemy species in host finding behavior , and th e d ifferent buckwheat arrangements may have also affected host finding behavior. T he squash plants in buckwheat arrangement B, where buckwheat was planted in the middle of squash, were smaller than the squash plants in buckwheat arrangement A, where buckw heat was alternati ng on either side of the squash, which suggests that competition between squash and buckwheat was greater in buckwheat arrangement B treatments compared with buckwheat arrangement A treatments . There was no significant difference in plant size between buckwheat arrangement A and the bareground treatment , which suggests that competition between buckwheat and the zucchini crop was minimized in buckwheat arrangement A compared with the other buckwheat treatments. Ultimately, marketable yields were not significantly different between the bareground treatment and buckwheat arrangements A and B. This finding suggests that manipulating the buckwheat spacing within the squash crop minimized the competition between the main crop and the living mulch and improved yields compared with the buckwheat arrangement C intercropping tactic that had been implemented previously by Nyoike and Liburd (2010). Ultimately, buckwheat arrangement A is recommended when intercropping buckwheat and squash for the purpose of reducing competition between buckwheat and squash plants and providing a

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145 more cost effective option when integrating buckwheat into an organic squash production system. I ncorporating multiple squash varieties was an effective strategy for suppressing pest pop ulations and disease incidence . However, a significant reduction in marketable yields was observed in the mixed varieties treatment compared with the other treatments. Observations of significant reduction s in pest densities and virus incidence in the mixe d varieties treatment suggest that this could be an effective strategy ; however future studies should focus on incorporating higher yie lding varieties . There were no significant differences among treatments with similar intercropping tactics when consideri ng the effect of D. catalinae on pest populations, disease incidence, and zucchini yield. This finding may suggest that there is movement of D. catalinae between plots into areas where it is not released, which is supported by observations of D. catalinae in plots where it was not released. Therefore, it was difficult to determine the effectiveness of D. catalinae on whitefly populations in the field. Future research should consider alternative methods to evaluating the effect of D. catalinae on whitefly po pulations in the field, such as the use of exclusion cages around treatment plots. In the organically approved insecticide study, M Pede® and PyGanic® were effective in significantly reducing adult whitefly populations. M Pede® was effective at reducing i mmature whitefly populations, but there could also be a property of the insecticidal soap that is interfering with feeding by D. catalinae . Delphastus catalinae populations were reduced when released 1 d post insecticide application, however, there was l ittle reduction at 5 d post application. Therefore, it is recommended that D.

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146 catalinae should not be released within 1 d of spraying M Pede® and PyGanic® insecticides for maximum whitefly control. Based on the findings, significant reductions in ad ult and immature whitefly populations were observed when applying PyGanic® with a delayed release (3 5 d) of D. catalinae . This project utilized several pest management strategies for the control of aphids and whiteflies in organic squash production. The goal of this research is to incorporate several pest management strategies to provide a comprehensive IPM program for organic squash growers. By adjusting the timing of incorporation and arrangement of buckwheat as an intercrop within squash, increased yi elds were demonstrated in squash compared to previous buckwheat intercropping arrangements used in Nyoike and Liburd (2010) . However , observations of yields in buckwheat arrangements A and B were not consistently different compared with the bareground trea tment. W hen used in conjunction with other pest management tactics, such as biological control and pesticides approved for organic use , enhanced pest and disease suppression could be achieved. It will be important to integrate several control tactics that target all life stages of whiteflies and aphids and that can provide adequate pest suppression throughout the growing season. With the added benefits of increased natural enemy densities that were observed in buckwheat, a reduction in pest and disease inci dence and an increase in yields could be achieved. Furthermore, findings from this research on the effectiveness of insecticides approved for organic production for managing silverleaf whitefly on organic squash , as well as the compatibility of these insec ticides with natural enemies including D. catalinae , will provide additional information on how these

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147 insecticides can be used in combination with natural enemies to regulate pest populations in organic production systems.

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148 LIST OF REFERENCES Adkins, S., C. G. Webster, C. S. Kousik, S. E. Webb, P. D. Roberts, P. A. Stansly, and W. W. Turechek. 2011. Ecology and management of whitefly transmitted viruses of vegetable crops in Florida. Virus Res. 159: 110 114. Akad, F. S., S. Webb, T. W. Nyoike, O. E. L iburd, W. Tucharek, S. Adkins, and J. E. Polston. 2008. Detection of Cucurbit leaf crumple virus in Florida. Plant Dis. 92: 648. Altieri, M. A. 1999. The ecological role of biodiversity in agroecosystems. Agr. Ecosys. Environ. 74: 19 31. Andow, D. A. 199 1. Vegetational diversity and arthropod population response. Ann. Rev. Entomol. 36: 561 596. Combinations of several insecticides used for integrated control of Colorado potato beetle ( Leptinotarsa decemlineata , Say., Coleoptera: Chrysomelidae). J. Pest Sci . 79 : 223 232. Blua, M. J. and T. M. Perring. 1989. Effect of zucchini yellow mosaic virus on development and yield of cantaloupe ( Cucumis melo ). Plant Dis. 73: 317 320. Bugg, R. L. 1991. Cover crops and control of arthropod pests of agriculture, pp. 157 163. In W. L. Harg rove (ed.), Cover crops for clean water. Soil and Water Conservation Society, Ankeny, AK. Buss, E. A. and S. G. Park Brown. 2002. Natural Products for Insect Pest Management. ENY 350, IFAS Extension, University of Florida, Gainesville, FL. Byrne, D. N. a nd T. S. Bellows Jr. 1991. 431 4 57 . Cantliffe, D. J., N. L. Shaw, and P. J. Stofella. 2007. Current trends in cucurbit production in the US. Proceedings of the IIIrd Symposium on Cucurbits 731: 473 478. Capinera, J. L. 2001. Green Peach Aphid, Myzus persicae (Sulzer) (Insecta: Hemiptera: Aphididae). EENY 222, IFAS Extension University of Florida, Gainesville, FL. Capinera, J. L. 2009. Melon aphid or cotton aphid, Aphis gossypii Glover (Insecta: Hemiptera: Aphidid ae). EENY 173, IFAS Extension, University of Florida, Gainesville, FL.

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150 Diaz, B. M. and A. Fereres. 2007. Ultraviolet blocking materials as a physical barrier to control insect pests and plant pathogens in protected crops. Pest Technol. 1: 85 95. Dow Chemical Company. 2 001. Spinosad Technical Bulletin. Dow AgroSciences, Indianapolis, Indiana, p. 3. Florida Department of Agriculture and Consumer Services (FDACS). 2013. Florida agriculture by the numbers 2013. Division of Marketing and Development. Tallahassee, FL. 180p. Foster, S. P., I. Denholm, and R. Thompson. 2002. Variation in response to neonicotinoid insecticides in peach potato aphids, Myzus persicae (Hemiptera:Aphididae). Pest Manag. Sci. 59: 166 173. Frank, D. L. and O. E. Liburd. 2005. Effects of living and s ynthetic mulch on the population dynamics of whiteflies and aphids, their associated natural enemies, and insect transmitted plant diseases in zucchini. Environ. Entomol. 34: 857 865. Gaolach, B. 2002. Impacts of undersowing clover and arugula on insect a bundance in broccoli. Organic Farming Research Foundation Project Report #00 17. Gerling, D. 1990. Whiteflies: Their Bionomics, Pest Status and Management. Athenaeum Press, New Castle, UK, 348pp. Gibson, R. M., and A. D. Rice. 1989. Modifying aphid behav iour, pp. 209 224. In A. K. Minks and P. Harrewijn [eds.], Aphids: their biology, natural enemies and control. Elsevier, Amsterdam. Gordon, R. D. 1994. South American Coccinellidae (Coleoptera). Part III: taxonomic revision of the western hemisphere genus Delphastus Casey. Frustula Entomol. 17: 71 133. Greathead, A. H. 1986. Host plants, pp. 17 26 . In Cock, M. J. W. (Ed.), Bemisia tabaci A Literature Survey on the Cotton Whitefly with an Annotated Bibliography. CAB International Institutes, Biolog ical C ontrol. Silkwood Park, UK . Hassan, S. A. 1994. Strategies to select Trichogramma species for use in biological control, pp. 55 71. In Wajnberg, E., and S. A. Hassan (Eds.) Biological control with egg parasitoids. CAB International, Wallingford, UK.

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151 Hei nz, K. M., J. R. Brazzle, M. P. Parrella, and C. H. Pickett. 1999. Field evaluations of augmentative releases of Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) for suppression of Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) in festing cotton. Biol. Control 16: 241 251. Hilje, L. and P. A. Stansly. 2008. Living ground covers for management of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) and tomato yellow mottle virus (ToYMoV) in Costa Rica. Crop Prot. 27: 10 16. Hilje, L ., H. S. Costa, and P. A. Stansly. 2001. Cultural practices for managing Bemisia tabaci and associated viral diseases. Crop Prot. 20: 801 812. Hoelmer, K. A. and C. H. Pickett. 2003. Geographic origin and taxonomic history of Delphastus spp. (Coleoptera: Coccinellidae) in commercial culture. Biocontrol Sci Technol 13: 529 535. Hoelmer, K. A., L. S. Osborne, and R. K. Yokomi. 1993. Reproduction and feeding behavior of Delpastus pusillus (Coleoptera: Coccinellidae) a predator of Bemisia tabaci (Homoptera: A lyerodidae). J. Econ. Entomol. 86: 322 329. Hollingsworth, R. G., B. E. Tabashnik, D. E. Ullman, M. W. Johnson, and R. Messing. 1994. Resistance of Aphis gosypii (Homoptera: Aphididae) to insecticides in Hawaii: spatial patterns and relation to insecticid e use. J. Econ. Entomol. 87 : 293 300. Hooks, C. R. R. and M. W. Johnson. 2004. Using undersown clovers as living mulches: Effects on yields, lepidopterous pest infestations, and spider densities in a Hawaiian broccoli agroecosystem. Internat. J. Pest Mana g. 50: 115 120. Hooks, C. R. R. and M. G. Wright. 2008. Use of living and dying mulches as barriers to protect zucchini from insect caused viruses and phytotoxemias. Plant Dis. 36: 1 8. Hooks, C. R. R., H. R. Valenzuela, and J. Defrank. 1998. Incidence o f pests and arthropod natural enemies in zucchini grown with living mulches. Agric. Ecosyst. Environ. 69: 217 231. Inbar, M. and D. Gerling. 2008. Plant mediated interactions between whiteflies, herbivores, and natural enemies. Annu. Rev. Entomol. 53: 431 448. Jones, D. R. 2003. Plant viruses transmitted by whiteflies. Eur. J. Plant Pathol. 109: 195 219. Kessing, J. L. M. and R. F. L. Mau. 2007. Aphis gossypii (Glover). Department of Entomology, University of Hawaii, Honolulu, Hawaii.

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152 Kucharek, T. and D . Purcifull. 2001. Aphid transmitted viruses of cucurbits in Florida. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, Circular 1184. Landis, D. A., S. D. Wratten, and G. M. Gurr. 2000. Habitat management to conserve nat ural enemies of arthropod pests in agriculture. Ann. Rev. Entomol. 45: 175 201. Langdale, G. W., R. L. Blevins, D. L. Karlen, D. K. McCool, M. A. Nearing, E. L. Skidmore, A. W. Thomas, D. D. Tyler, and J. R. Williams. 1991. Cover crop effects on soil eros ion by wind and water, pp. 15 22. In W. L. Hargrove (ed.), Cover crops for clean water. Soil and Water Conservation Society, Ankeny, AK. Lecoq, H., M. Pitrat, and M. Cle'ment. 1981. potyvirus provoquant la maladie du rabougrissement jaune du melon. Agronomie 1: 827 834. Legaspi, J. C., A. M. Simmons, and B. C. Legaspi. 2006. Prey preference of Delphastus catalinae (Coleoptera: Coccinellidae) on Bemisia argentifolii (Homoptera: Aleyrodidae): effects of plant species a nd prey stages. Fla. Entomol. 89: 218 222. Liburd, O. E. and T. W. Nyoike. 2008. Biology and management of whiteflies in sustainable field production of cucurbits. ENY 848/IN762, IFAS Extension, University of Florida, Gainesville, FL. Liburd, O. E. 2012. Evaluation of OMRI approved insecticides for control of silverleaf whitefly, Bemisia tabaci in organic squash. IR 4, Gainesville, FL. Liu, T. X., and P. A. Stansly. 1995. Toxicity of biorational insecticides to Bemisia argentifolii (Homoptera: Aleyrodida e) on tomato leaves. J. Econ. Entomol. 88: 564 568. Liu, T. X., and P. A. Stansly. 1999. Searching and feeding behavior of Nephaspis oculatus and Delphastus catalinae (Coleoptera:Coccinellidae), predators of Bemisia argentifolii (Homoptera: Aleyrodidae). Environ. Entomol. 28: 901 906. Liu, T. X., and P. A. Stansly. 2000. Insecticidal activity of surfactants and oils against silverleaf whitefly ( Bemisia argentifolii ) nymphs (Homoptera: Aleyrodidae) on collards and tomato. Pest Manag. Sci. 56: 861 866. Luc as, E. 2005. Intraguild predation among aphidophagous predators. Eur. J. Entomol. 102: 351 364.

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153 Manandhar, R., C. R. R. Hooks, and M. G. Wright. 2009. Influence of cover crop and intercrop systems on Bemisia argentifolii (Hemiptera: Aleyrodidae) infestat ion and associated squash silverleaf disorder in zucchini. Environ. Entomol. 38: 442 449. Marino, P. C. and D. A. Landis. 1996. Effect of landscape structure on parasitoid diversity and parasitism in agroecosystems. Ecol. Appl. 6: 276 284. Maxwell, E. an d H. Y. Fadamiro. 2006. Evaluation of several reduced risk insecticides in combination with an action threshold for managing lepidopteran pests of cole crops in Alabama. Fla. Entomol. 89: 117 126. McAuslane, H. J., J. Chen, R. B. Carle, and J. Schmalstig. 2004. Inlfuence of Bemisia argentifolii (Homoptera: Aleyrodidae) infestation and squash silverleaf disorder on zucchini seedling growth. J. Econ. Entomol. 97: 1096 1105. McCraw, D. and J. E. Motes. 2007. Use of Plastic Mulch and Row Covers in Vegetable P roduction. Oklahoma Cooperative Extension Service, Division of Agricultural and Natural Resources, Oklahoma State University, HLA 6034. McNeill, C. A., O. E. Liburd, and C. A. Chase. 2012. Effect of cover crops on aphids, whiteflies and their associated n atural enemies in organic squash. J. Sustain. Agr. 36: 382 403. Mossler, M. A. and O. N. Nesheim. 2001. Florida crop/pest management profile: squash. Florida cooperative extension service, Institute of Food and Agricultural Sciences, University of Florida . Nauen, R., N. Stumpf, and A. Elbert. 2002. Toxicological and mechanistic studies on neonicotinoid cross resistance in Q type Bemisia tabaci (Hemiptera: Aleyrodidae). Pest Manag. Sci. 58: 868 875. Ninkovic, V., U. Olsson, and J. Pettersson. 2002. Mixed barley cultivars affects aphid host plant acceptance in field experiments. Entomol. Exp. Appl. 102: 177 182. Nomikou, M., A. Janssen, R. Schraag, and M. W. Sabelis. 2001. Phytoseiid predators as potential biological control agents for Bemisia tabaci . Exp. Appl. Acarol. 25: 271 291. Nyoike, T. W. and O. E. Liburd. 2010. Effect of living (buckwheat) and UV reflective mulches with and without imidacloprid on whiteflies, aphids and marketable yields of zucchini squash. Int. J. Pest Manage. 56: 31 39.

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156 Zalom, F. G. 1981. Effects of aluminum mulch on fecundity of apterous Myzus persicae on head lettuce in a field planting. Ent. Exp. Appl. 30: 227 230. Zhao, J. Z., G. S. Ayers, E. J. Grafius, and F. W. Stehr. 1992. Effects of neighboring nectar producing plants on populations of pest lepidoptera and their parasitoids in broccoli plantings. Great Lakes Entomol. 25: 253 258.

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157 BIOGRAPHICAL SKETCH Janine is from Boonton Township, NJ. She rec eived her Bachelor of Arts degree in environmental s cience from the New College of Florida in 2008. She attended the University of Delaware and g raduated i n 2010 with a Master of Science degree in e ntomology. At the University of Delaware, she conducted research on the dispersal behavior of neonate European corn borer on transgenic corn. Janine received her PhD in entomology at the University of Florida in A ugust 2014 working under the supervision of Dr. Oscar Liburd. Her research focus was on regulating whitefly populations in organic squash production by implementing several conservation practices including the use of natural enemies , living mulches, and or ganically approved pesticides . interests are in conservation and sustainable practices within agricultural systems, and her future career goals are to conduct research and extension services related to IPM in diversified agroecosystems.