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Herbicide Use in Grafted Triploid Watermelon [Citrullus Lanatus (Thunb.) Matsumura and Nakai]

Permanent Link: http://ufdc.ufl.edu/UFE0043680/00001

Material Information

Title: Herbicide Use in Grafted Triploid Watermelon Citrullus Lanatus (Thunb.) Matsumura and Nakai
Physical Description: 1 online resource (69 p.)
Language: english
Creator: Adkins, Joshua
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: clomazone -- grafted -- grafting -- halosulfuron -- herbicide -- s-metolachlor -- terbacil -- translocation -- uptake -- watermelon
Horticultural Science -- Dissertations, Academic -- UF
Genre: Horticultural Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Grafting may serve as an alternative to methyl bromide fumigation for soil-borne pest control. Field and laboratory experiments were conducted to examine the use of herbicides in grafted watermelon. The impact of terbacil, halosulfuron, clomazone, and S-metolachlor on field production of triploid watermelon grafted onto bottle gourd and interspecific hybrid squash rootstocks was evaluated in Florida, South Carolina, and North Carolina. Each herbicide was applied pre-transplant (PRE). Halosulfuron was also applied post-transplant (POST). Non-grafted watermelon and untreated control plots were also included. Overall, grafted watermelons responded to herbicides in a similar manner as non-grafted watermelons. No injury was reported from terbacil or halosulfuron PRE at Florida or South Carolina. Injury from clomazone, S-metolachlor, and halosulfuron POST was seen at various levels of severity. Injured plants usually recovered to produce overall yields similar to untreated plants. However, early yield reductions were seen in some trials. Herbicide uptake and translocation was evaluated in grafted watermelon using soil applied 14C-atrazine and foliar applied 14C-glyphosate. Treatments were made to watermelon grafted onto bottle gourd and interspecific hybrid squash. Non-grafted and self-grafted watermelon were also included. Greater atrazine uptake was seen in watermelon grafted onto interspecific hybrid squash compared to other rootstocks and non-grafted watermelon. When examining the translocation of absorbed atrazine, non-grafted and self-grafted watermelon had a slightly higher percentage of absorbed atrazine reach the shoot compared to watermelon grafted onto bottle gourd and interspecific hybrid squash. No significant differences were observed in glyphosate uptake or translocation when comparing among the grafted and non-grafted plants.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Joshua Adkins.
Thesis: Thesis (Ph.D.)--University of Florida, 2011.
Local: Adviser: Olson, Stephen M.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043680:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043680/00001

Material Information

Title: Herbicide Use in Grafted Triploid Watermelon Citrullus Lanatus (Thunb.) Matsumura and Nakai
Physical Description: 1 online resource (69 p.)
Language: english
Creator: Adkins, Joshua
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: clomazone -- grafted -- grafting -- halosulfuron -- herbicide -- s-metolachlor -- terbacil -- translocation -- uptake -- watermelon
Horticultural Science -- Dissertations, Academic -- UF
Genre: Horticultural Science thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Grafting may serve as an alternative to methyl bromide fumigation for soil-borne pest control. Field and laboratory experiments were conducted to examine the use of herbicides in grafted watermelon. The impact of terbacil, halosulfuron, clomazone, and S-metolachlor on field production of triploid watermelon grafted onto bottle gourd and interspecific hybrid squash rootstocks was evaluated in Florida, South Carolina, and North Carolina. Each herbicide was applied pre-transplant (PRE). Halosulfuron was also applied post-transplant (POST). Non-grafted watermelon and untreated control plots were also included. Overall, grafted watermelons responded to herbicides in a similar manner as non-grafted watermelons. No injury was reported from terbacil or halosulfuron PRE at Florida or South Carolina. Injury from clomazone, S-metolachlor, and halosulfuron POST was seen at various levels of severity. Injured plants usually recovered to produce overall yields similar to untreated plants. However, early yield reductions were seen in some trials. Herbicide uptake and translocation was evaluated in grafted watermelon using soil applied 14C-atrazine and foliar applied 14C-glyphosate. Treatments were made to watermelon grafted onto bottle gourd and interspecific hybrid squash. Non-grafted and self-grafted watermelon were also included. Greater atrazine uptake was seen in watermelon grafted onto interspecific hybrid squash compared to other rootstocks and non-grafted watermelon. When examining the translocation of absorbed atrazine, non-grafted and self-grafted watermelon had a slightly higher percentage of absorbed atrazine reach the shoot compared to watermelon grafted onto bottle gourd and interspecific hybrid squash. No significant differences were observed in glyphosate uptake or translocation when comparing among the grafted and non-grafted plants.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Joshua Adkins.
Thesis: Thesis (Ph.D.)--University of Florida, 2011.
Local: Adviser: Olson, Stephen M.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043680:00001


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1 HERBICIDE USE IN GRAFTED TRIPLOID WATERMELON [ Citrullus lanatus (Thunb.) Matsumura and Nakai] By JOSHUA IRA ADKINS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2011

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2 2011 Joshua Ira Adkins

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3 To my p arents

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4 ACKNOWLEDGMENTS Numerous individuals helped me throughout this Doctor of Philosophy program. I especially than k my advisor, Dr. Stephen Olson, for his research guidance and support. I am also very thankful for the continued support of Dr. William Stall throughout graduate school. My sincere gratitude also goes to the other members of my committee: Dr. Gregory Ma cDonald, Dr. Bielinski Santos, and Dr. Andrew MacRae. I also thank Dr. Jason Ferrell for his guidance. I appreciate the efforts of everyone at the North Florida Research and Education Center Quincy, especially the tremendous effort of Lee Carter during watermelon harvest. I thank Robert Querns for all of his help in the laboratory. For the assistance of Charles Barrett and many other graduate students in the Horticultural Sciences Department, I am grateful. I thank my parents, Mike and Christi Adkins, for their constant love and support. Most importantly, I thank God for providing me with this wonderful opportunity.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ ........... 4 LIST OF TABLES ................................ ................................ ................................ ...................... 7 LIST OF FIGURES ................................ ................................ ................................ .................... 9 ABSTRACT ................................ ................................ ................................ ............................. 10 1 LITERATURE RE VIEW ................................ ................................ ................................ ... 12 Herbicides of Interest ................................ ................................ ................................ ......... 13 Terbacil ................................ ................................ ................................ ....................... 13 Halosulfuron methy l (Halosulfuron) ................................ ................................ ............ 14 Clomazone ................................ ................................ ................................ .................. 15 S metolachlor ................................ ................................ ................................ .............. 15 Previous Herbi cide Studies in Grafted Cucurbits ................................ ................................ 16 Methods to Study Herbicide Uptake and Translocation ................................ ...................... 17 Autoradiography ................................ ................................ ................................ ......... 17 Liquid Scintillation Spectrometry ................................ ................................ ................ 18 Radiolabeled Herbicides Available for Use ................................ ................................ ........ 19 Atrazine ................................ ................................ ................................ ...................... 20 Glyphosate ................................ ................................ ................................ .................. 20 2 TERBACIL, HALOSULFURON, CLOMAZONE, AND S METOLACHLOR EFFECT ON GRAFTED TRIPLOID WATERMELON IN FLORI DA ................................ ............. 21 Objective ................................ ................................ ................................ ............................ 21 Materials and Methods ................................ ................................ ................................ ....... 21 Results and Discussi on ................................ ................................ ................................ ....... 23 3 TERBACIL, HALOSULFURON, CLOMAZONE, AND S METOLACHLOR EFFECT ON GRAFTED TRIPLOID WATERMELON IN SOUTH CAROLINA ............................ 33 Objectiv e ................................ ................................ ................................ ............................ 33 Materials and Methods ................................ ................................ ................................ ....... 33 Results and Discussion ................................ ................................ ................................ ....... 35 4 TERBAC IL, HALOSULFURON, CLOMAZONE, AND S METOLACHLOR EFFECT ON GRAFTED TRIPLOID WATERMELON IN NORTH CAROLINA ........................... 42 Objective ................................ ................................ ................................ ............................ 42 Materials and Methods ................................ ................................ ................................ ....... 42 Results and Discussion ................................ ................................ ................................ ....... 43

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6 5 HERBICIDE UPTAKE AND TRANSLOCATION IN GRAFTED TRIPLOID WATERMELON ................................ ................................ ................................ ............... 48 Objective ................................ ................................ ................................ ............................ 48 Materials and Methods ................................ ................................ ................................ ....... 48 Plant Material ................................ ................................ ................................ .............. 48 Herbicide Treatment ................................ ................................ ................................ .... 49 Harvest ................................ ................................ ................................ ........................ 49 Autoradiography ................................ ................................ ................................ ......... 50 Liquid Scintillation Spectrometry ................................ ................................ ................ 50 Experimental Design and Data Analysis ................................ ................................ ...... 50 Results and Discussi on ................................ ................................ ................................ ....... 51 Autoradiography ................................ ................................ ................................ ......... 51 Liquid Scintillation Spectrometry Uptake ................................ ................................ 51 Liquid Scintillation Spectrometry Translocation ................................ ....................... 52 6 CONCLUSIONS ................................ ................................ ................................ ................ 62 LITERATURE CITED ................................ ................................ ................................ ............. 65 BIOGRAPHICAL SKETCH ................................ ................................ ................................ ..... 69

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7 LIST OF TABLES Table page 2 1 Clomazone and S metolachlor injury in Florida at 17 days after transplanting. ............... 26 2 2 Effect of herbic ide treatments on vine length in Florida at 25 days after transplanting. ... 27 2 3 Stem spli tting from h alosulfuron POST application in Florida at 6 days after application. ................................ ................................ ................................ .................... 28 2 4 Effect of herbicide treatment on node count of the last 20 cm of the distal end of vines in Florida at 2 5 days after transplanting. ................................ ............................... 29 2 5 Effect of herbicide treatment on early and total yield in Florida expressed as kg per plant. ................................ ................................ ................................ ............................. 30 2 6 Effect of herbicide treatment on early and total yie ld in Florida expressed as number of fruit per plant. ................................ ................................ ................................ ............ 31 2 7 Effect of herbicide treatment on fruit s ize in Florida ................................ ..................... 32 3 1 Clomazone injury in South Carolina at 20 days after transplanting in 2009. ................... 36 3 2 Effect of herbicide treatmen ts on vine length in South Carolina at 20 days after transplanting in 2009. ................................ ................................ ................................ .... 37 3 3 Halosulfuron POST injury in South Carolina at 9 days after application in 2010. ........... 38 3 4 Effect of herbicide treatment on early and total yield in South Carolina expressed at kg per plant. ................................ ................................ ................................ ................... 39 3 5 Effect of herbicide treatment on early and total yie ld in South Caroli na expressed as number of fruit per plant. ................................ ................................ ............................... 40 3 6 Effect of herbicide treatment on fruit s ize in South Carolina ................................ ......... 41 4 1 Effect o f herbicide treatment on early and total yi eld in North Carolina expressed as kg per plant. ................................ ................................ ................................ ................... 45 4 2 Effect of herbicide treatment on early and total yield in North Carolina expressed as number of fruit per plant. ................................ ................................ ............................... 46 4 3 Effect of herbicide treatment on fruit size in North Carolina ................................ ......... 47 5 1 Sources of materials used in gr afted watermelon uptake and translocation study. ........... 54 5 2 Uptake and translocation of 14 C atrazine at 24 and 72 hours after treatment in trial 1. .... 59

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8 5 3 Uptake and translocation of 14 C atrazine at 24 and 72 hours after treatment in trial 2. .... 59 5 4 Uptake and translocation of 14 C glyphosate at 24 and 72 hours after treatm ent in trial 1. ................................ ................................ ................................ ................................ ... 60 5 5 Uptake and translocation of 14 C glyphosate at 24 and 72 hours after treatment in trial 2. ................................ ................................ ................................ ................................ ... 60 5 6 Trial 1 average dry weights of roots and shoots. ................................ ............................. 61 5 7 Trail 2 average dry weights of roots and shoots. ................................ ............................. 61

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9 LIST OF FIGURES Figure page 5 1 Trial 1 autoradiographs of 14 C atrazine treated plants at 24 and 72 hours after treatment. ................................ ................................ ................................ ...................... 55 5 2 Trial 2 pressed plants (left) and autoradio graphs (right) of 14 C atrazine treated plants at 24 and 72 hours after treatment. ................................ ................................ ................. 56 5 3 Trial 1 autoradiographs of 14 C glyphosate treated plants at 24 and 72 hours after treatment. ................................ ................................ ................................ ...................... 57 5 4 Trial 2 pressed plants (left) and autoradiographs (right) of 14 C glyphosate treated plants at 24 and 72 hours after treatment. ................................ ................................ ....... 58

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10 Abstract of Dissertation Prese nted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy HERBICIDE USE IN GRAFTED TRIPLOID WATERMELON [ Citrullus lanatus (Thunb.) Matsumura and Nakai] By Jos hua Ira Adkins December 2011 Chair: Stephen M. Olson Major: Horticultural Science Grafting may serve as an alternative to methyl bromide fumi gation for soil borne pest control. Field and laboratory experiments were conducted to examine the use of herbi cides in grafted watermelon. T he impact of terbacil, halosulfuron, clomazone, and S metolachlor on field production of triploid watermelon grafted onto bottle gourd and interspecific hybrid squash rootstocks was evaluated in Florida, South Carolina, and N orth Carolina Each herbicide was applied pre transplant (PRE). Halosulfuron was also applied post transplant (POST). Non gr afted watermelon and untreated control plots were also included. Overall, grafted watermelons responded to herbicides in a simil ar man ner as non grafted watermelons. No injury was reported from terbacil or halosulfuron PRE at Florida or South Carolina. Injury from clomazone, S metolachlor, and halosulfuron POST was seen at various levels of severity Injured plants usually recov ered to produce overall yields similar to untreated plants. However, ear ly yield reductions were seen in some trials Herbici de uptake and translocation was evaluated in grafted watermelon using soil applied 14 C atrazine and foliar applied 14 C glyphosate. Treatments were made to watermelon grafted onto bottle gourd and interspecific hybrid squash. Non graf ted and self grafted watermelon were also included. Greater atrazine uptake was seen in watermelon grafted onto

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11 interspecific hybrid squash compared t o other rootstocks and non grafted watermelon When examining the translocation of absorbed atrazine, non grafted and self grafted watermelon had a slightly higher percentage of absorbed atrazine reach the shoot compared to watermelon grafted onto bottle gourd and interspecific hybrid squash. No significant differences were observed in glyphosate uptake or translocation when comparing among the grafted and non grafted plants.

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12 CHAPTER 1 LITERATURE REVIEW Watermelon [ Citrullus lanatus (Thunb.) Matsumura and Nakai] is thought to be the first grafted vegetable crop grown on a commercial scale (Kubota et al. 2008; Lee 1994). Early research and production using grafted watermelons took place in Japan and Korea over seven decades ago (Lee and Oda 2003). Whe n paired with the appropriate rootstock, watermelon plants may be imparted with a variety of beneficial characteristics. The primary reason to graft watermelons is to reduce dama ge from soil borne pests (Cushman 2006). Certain rootstocks are known to imp rove resistance or tolerance to fusarium wilt ( Fusarium oxysporum Schltdl.) verticillium wilt ( Verticillium dahliae Kleb.) root knot nematodes ( Meloidogyne spp.) and certain viral complexes (King et al. 2008; Miguel et al. 2004; Paplomatas et al. 2002; al. 2003). Furthermore, grafting may increase yield, quality, and tolerance to certain c onditions such as high salinity and low temperature (Alan et al. 2007; Chouka and Jebari 1999; Colla et al. 2007; Core 2005; Davis et al. 2008a; Goreta et a appropriate rootstock for specific conditions must be selected carefully to avoid a negative impact on the characteristics aforemention ed (Davis et al. 2008b). Rothenberger and Starbuck (2008) simply define that follows the uniting of compatible plants was summarized by Andrews and Serrano Marquez (1993). First, the ruptur ed cells at the graft union collapse and creat e a necrotic layer that disappears during subsequent events. Then living cells from the scion and rootstock extend into the necrotic layer. Via cell division, a callus bridge of interdigitating parenchyma ce lls forms, growing into the necrotic region. During these events, physical cohesion of the scion and rootstock increases the tensile strength of the graft. This process occurs as dictyosome mediated

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13 secretion of cell wall precursors assists in cohesion ( Andrews and Serrano Marquez 1993). A new vascular cambium subsequently differentiates from parenchyma cells. Finally, secondary xylem and phloem are created by the newly formed cambium, providing a vascular connection between the scion and rootstock. G ra fted watermelon plants ha ve not been utilized to a great extent in the United States thus far (Davis et al. 2008b). Ho wever, with the phase out of methyl bromide fumigation (mandated by the U.S. Clean Air Act and the Montreal Protocol on Ozone Depleting S ubstances ) and lower amount of available land for long term crop rotation, growers may consider grafting as an alternat ive for pest management (Noling et al. 2009) If watermelon growers do make a transition to using grafted plants, they will need to know which herbicides are safe to use on a plant composed of a scion of one plant ty pe and a rootstock of another. W ith the cost of grafted triploid watermelon transplants at approximately three ti mes that of non grafted triploid watermelon transplant s (Taylo r et al. 2006) growers cannot afford to risk herbicide damage to such an investment. The tolerance of grafted watermelons to herbicides labeled for use in the production of watermelon and other cucurbit crops that are closely related to rootstock materia l is widely unknown. Such herbicides include terbacil, halosulfuron, clomazone and S metolachlor. Herbicides of Interest Terbacil Terbacil [5 chloro 3 (1,1 dimethylethyl) 6 methyl 2,4 (1 H ,3 H ) pyrimidinedione] is a member of the uracil chemical family (Sen seman 2007). Uracil herbicides have a similar structure in that they are centered around a common six membered ring made up of four carbon atoms and two nitrogen atoms separated by one of the carbon atoms (Anderson 1996). One oxygen atom is attached by a double bond to the ring structure at the carbon atom between the

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14 two nitrogen atoms. Another oxygen atom is double bonded to the carbon atom found at the 4 position of the ring. A methyl group is bonded to the carbon at the 6 position. Terbacil differs from the other herbicide in the uracil family (bromacil) by having different substituents at the 3 position and 5 position of the ring. Terbacil inhibits electron transport in photosystem II (Anderson 1996; Senseman 2007). Following soil application, ter bacil is readily absorbed by roots and translocated upward int o the leaves. Terbacil is labeled in watermelon production for pre emergence, pre transplant, and row middle applications t o control broadleaf weeds (Anonymous 2009; Olson et al. 2011 ). Halosul furon methyl (H alosulfuron) Halosulfuron {methyl 3 chloro 5 [[[[(4,6 dimethoxy 2 pyrimidinyl)amino]carbonyl] amino]sulfonyl] 1 methyl 1 H pyrazole 4 carboxylate} is a member of the sulfonylurea chemical family (Senseman 2007). As indicated by the name, her bicides in the sulfonylurea family have a sulfonylurea nucleus (Anderson 1996). Herbicides with in this family are different based on the substituents bonded to that nucleus. Halosulfuron inhibits the enzyme acetolactate synthase or acetohydroxy acid synth ase (Anderson 1996; Senseman 2007). This herbicide is highly absorbed by roots and shoots. It is a weak acid and translocates in the xyle m and phloem. Halosulfuron is effective for the control of nutsedge ( Cyperus spp.) and certain broadleaf weeds and i s labeled in a variety of cucurbit crops for pre emergence, pre seeding, pre transplant, post transplant, and row middle weed control, depending on the particular crop (Anonymous 2007; Olson et al. 2011 ) Watermelon has a label for each of the aforementio ned halosulfuron applications except post transplant. Halosulfuron applied post transplant is known to cause stem splitting, shorter vines, and node stacking when applied to triploid ( seedless ) watermelon (Dittmar et al. 2008).

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15 Clomazone Clomazone {2 [(2 chlorophenyl)methyl] 4,4 dimethyl 3 isoxazolidinone} is the only herbicide in the isoxazolidinone chemical family (Senseman 2007). It is thought to be a pro herbicide that must be metabolized into its active 5 keto form. The active form inhibits 1 deoxy D xyulose 5 phosphate synthase which is a major component in plastid isoprenoid synthesis. Clomazone is highly absorbed by roots and emerging shoots (Anderson 1996; Senseman 2007). The herbicide is translocated in the xylem to the leaves. Clomazon e is labeled to control a variety of grasses and broadleaf weeds (Anonymous 2002 ). In Florida, it is recommended for pre emergence and row middle application in certain varieties of summer and winter squash (Olson et al. 2011 ). Clomazone is used for wate rmelon production in certain states although bleaching injury has been seen on many watermelon varieties (Grey et al. 2000; Harrison et al. 2010; Hohlt et al. 1990). S metolachlor S metolachlor {2 chloro N (2 ethyl 6 methylphenyl) N [(1 S ) 2 methoxy 1 methy ethyl] acetamide} is a member of the acid amide herbicide family (Anderson 1996). This is a diverse family including various chemistries. S meto lachlor may be more specifically referred to as a chloroacetamide (Senseman 2007). S metolachlor inhibits the biosynthesis of fatty acids, proteins, lipids, flavonoids, and isoprenoids. Herbicidal activity may involve the conjugation of acetyl coenzyme A. S metolachlor is absorbed by roots and shoots (Senseman 2007). Emerging weed seedlings are generally the applic ation target. S metolachlor is labeled for grass and broadleaf weed control in pumpk in ( Anonymous 2011 ; Olson et al. 2011 ). It may be applied inter row or inter hill prior to weed emergence following specialized instructions.

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16 Previous Herbicide St udies in Grafted Cucurbits Baker and Warren (1962) fo und that when non grafted squash ( Cucurbita pepo L.) and cucumber ( Cucumis sativus L.) plants were treated with chloramben (3 amino 2,5 dichlorobenzoic acid) via a nutrient solution, shoot growth of cucu mber was poor in comparison to squash. However, the shoot growth response was reversed when cucumber was g rafted onto squash rootstock and squash was grafted onto cucumber rootstock. Ther efore, scion tolerance of chloramben was dependent upon rootstock. The same study (Baker and Warren 1962) also examined the tran s location of radiolabeled chloramben in non grafted cucumber, cucumber grafted onto cucumber, cucumber grafted onto squash, non grafted squash, squash grafted onto squash, and squash grafted onto cucumber. Non grafted cucumber had a much greater concentration of chloramben in the shoot compared to non grafted squash when chloram ben was taken up in a nutrient solution. When cucumber and squash were grafted onto their own r oot system, somewhat les s chloramben entered the shoot compared to the non gr afted plants. Therefore, chloramben movement from root to shoot appeared to have been slightly limited by the graft union. Cucumber h ad a much lower amount of chloramben reach the shoot when grafted on to squash rootstock compared to cucumber rootstock or non grafted cucumber. Squash ha d a much higher amount of chloramben reach the shoot when grafted onto cucumber rootstock compared to squash rootstock or non grafted squ ash. In conclusion, more chloram ben entered plants through cucumber roots compared to squash roots. Several herbicides were evaluated for use in grafted watermelon by Cohen et al. (2008). Experiments were conducted using non grafted watermelon, watermelon grafted onto interspecific hybr id squash ( Cucurbita maxima x C. moschata ) rootstock, and interspecific hybrid squash rootstock alone. Herbicides were applied to soil in pots via a simulated drip

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17 irrigation system in a greenhouse. The active ingredients of two herbicides evaluated, eth alfluralin [ N ethyl N (2 methyl) 2 propenyl) 2,6 dinitro 4 (trifluoromethyl)benzenamine] and clomazone, are labeled for use in certain cucurbits in Florida. Ethalfluralin was reported to be safe for use in watermelon grafted onto interspecific hybrid squa sh rootstock. Although clomazone caused no bleaching to the interspecific hybrid squash rootstock when tested alone, bleaching was present in the scion when clomazone was applied to watermelon grafted onto interspecific hybrid squash rootstock. Methods to Study Herbicide Uptake and Translocation Radio active herbicides have been used for the study of herbicide uptake and translocation for over 50 years. One of the radioactive isotopes commonly employed in these studies is carbon 14, a beta emitter (Corb i n and Swisher 1986). Carbon 14 ( 14 C) is well suited for laboratory experiments because of its long half life and the ability to easily shield its beta rays (Yamaguchi and Crafts 1958). It is possible to trace very small amounts of atoms using 14 C labeled h erbicides since the position of the labeled atoms is known with certainty as a result of the synthesis methods used to make the compound (Corb i n and Swisher 1986). Two of the primary techniques using 14 C labeled herbicides to study herbicide uptake and tr anslocation are autoradiography and liquid scintillation spectrometry. Autoradiography image that can be used to determine the location and relative concentration of a radiolabeled herbicide in plant tissue (Eastin 1986; Yamaguchi and Crafts 1958). Autoradiographs are created by following a relatively uncomplicated set of procedures (Wehtj e et al. 2007). The radiolabeled herbicide is applied to the plants. Following a suitable period for uptake and translocation, plants are

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18 harvested, pressed, dried, and fastened to cardboard such as the protocol for a taxonomic mount. The mounted plant is pressed against X ray film and covered to keep out light. After an appropriate exposure time (usually 2 to 4 weeks), film is developed and the autoradiograph is revealed (Eastin 1986; Wehtje et al. 2007). The X a radiation sensitive emulsion layer Microscopic crystals of AgCl, AgBr, or mixtures of silver halides are found within the emulsion layer. The gelatin layers act as a medium for homogeneous dispersal of the halide crystals (Corbin and Swisher 1986). Furthermore, they allow for rapid penetration of developer and fixer chemicals. After development, the image may range in intensity from a light trace to a black line o r mass (Yamaguchi and Crafts 1958). By examining the intensity of the image, an estimate of the amount of radiolabeled herbicide present may be made. As an alternative to X ray film, phosphorescence imaging may also be used to create autoradiographs (Weht je et al. 2007). This technique uses the direct transfer of energy emitted from phosphorescing dyes and/or from radioactive isotope decay to a phosphor coated storage screen. The radioactive energy is converted to light energy that may be detected and an alyzed using a series of photosensitive detectors located within the phosphorescence imaging scanner (Wehtje et al. 2007). Liquid Scintillation Spectrometry Liquid scintillation spectrometry is a means of evaluating herbicide up t ake and translocation by nu merically quantifying the amount of radiolabeled herbicide in a plant (Wehtje et al. 2007). Liquid scintillation counters, which vary in complexity, are one of the most sensitive instruments available to analyze small amounts of radiolabeled herbicides (C orbin and

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19 Swisher 1986). This technique is 80 to 90% efficient in the detection of beta particles emitted by 14 C (Eastin 1986). Many of the early steps for this method are the same as for the autoradiography technique. After treating the plants with radi olabeled herbicide, plants are harvested, divided into appropriate sections, dried, and weighed (Eastin 1986). Subsequently, each plant part is prepared for scintillation counting either by homogenizing the sample and taking a portion to add directly into the scintillation cocktail or by combusting the sample into 14 CO 2 that is trapped and added to scintillation cocktail for counting. The scintillation cocktail is a solution of fluors (dissolved scintillator solutes) in an organic solution that absorbs th e radioactive particle energy (Eastin 1986). The primary and secondary fluors in the cocktail reemit the energy as light of specific wavelengths. A charge pulse is produced by a photomultiplier in response to the light energy. Using a scaling circuit, t he charge pulse can be amplified and counted (Eastin 1986). Radiolabeled Herbicides Available for Use A variety of radiolabeled herbicides have been produced for research purposes. In order to study the impact of grafting on herbicide uptake and transloca tion, it would be of interest to examine a xylem mobile herbicide applied to the soil and a phloem mobile herbicide applied to the foliage. Although atrazine [6 chloro N ethyl N (1 methylethyl) 1,3,5 triazine 2,4 diamine] and glyphosate [ N (phosphonomethy l)glycine] are not l abeled for direct application to cucurbit crops, 14 C atrazine and 14 C glyphosate were available for use in the laboratory. These compounds were appropriate to use in an experiment on grafted watermelon because of the known uptake and t ranslocation routes of each compound and not for any potential use in a production setting.

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20 Atrazine Atrazine is a member of the triazine herbicide family (Anderson 1996). The diamino s triazine herbicides are centered on a common six membered ring struct ure made up of three nitrogen and three carbon atoms arranged symmetrically in the ring. An amino group is bonded at the carbon atoms on the 4 and 6 positions of the ring. Three subgroups are found within the diamino s triazine herbicides. Each subgrou p is based on the substitution at the 2 position of the ring. Chlorine is the substitution for the subgroup (2 chloro 4,6 diamino s triazine) of which atrazine is a member. Atrazine is absorbed through roots and translocated in the xylem to the leaves in a manner similar to terbacil (Anderson 1996; Senseman 2007). Foliar absorption will occur from post emergence applications, especially with the use of adjuvants. However, atrazine does not translocate out of the leaves. The mode of action for atrazine i s the inhibition of electron transport in photosystem II (Anderson 1996; Senseman 2007). Glyphosate Glyphosate is an organophosphorus herbicide used for non selective weed control (Senseman 2007). After foliar absorption, glyphosate is translocated throug hout the plant as is halosulfuron (Anderson 1996). Glyphosate t ranslocation is primarily in the symplast with accumulation in meristems, immature leaves, and underground tissues (Senseman 2007). Glyphosate inhibits 5 enolpyruvylshikimate 3 phosphate syn thase in the shikimic acid pathway (Anderson 1996; Senseman 2007). As a result, the production of the aromatic amino acids tyrosine, tryptophan, and phenylalanine is inhibited (Senseman 2007) Each of these amino acids is needed for protein synthesis or for certain biosynthetic pathways that lead to plant growth.

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21 CHAPTER 2 TERBACIL, HALOSULFURON, CLOMAZONE, AND S METOLACHLOR EFFECT ON GRAFTED TRIPLOID WATERMELON IN FLORIDA Objective Herbicide tolerance of grafted watermelon [ Citrullus lanatus (Thunb.) Matsumura and Nakai] is widely unknown. The objective of this research was to examine the impact of terbacil, halosulfuron, clomazone, and S metolachlor on injury and yield of grafted triploid watermelon in Florida Materials and Methods Field experiments were conducted at the University of Florida North Florida Research and Education Center, Quincy, FL (NFREC) in the spring of 2009 and 2010. Soil type at NFREC is a Norfolk loamy sand (fine loamy, kaolinitic, thermic Typic Kandiudults). Raised beds used in the experiment were 0.81 m wide and established on 2.44 m centers. All fertilizer was applied pre plant at the rate of 153N 20P 127K kg ha 1 Prior to transplanting, beds were fumigated with methyl bromide and chloropicrin (98:2) at 269 kg ha 1 and co vered with black polyethylene mulch. Experimental design was a split plot with four replications. Main plot factor was herbicide all grafting combinations. Ro (BG) [ Lagenaria siceraria (Mol.) Standl.] ( Cucurbita maxima x C. moschata ) and non conducted using splice grafts. On April 9, 2009 and April 6, 2010, transplants were established at an in row spacing of 0.91 m. To provide viable pollen for fruit set, diploid pollenizers were transplanted in row at a 1:3 (pollenizer to triploid) ratio. All transplants were provided by Syngenta Full Count TM Plant Program, Naples, FL. Plots were irrigated via drip tape that was

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22 placed under the polyethylene mulch using University of Florida Institute of Food and Agricultural Sciences recommendations (Olson et al. 2007). Herbicide treatments included two rates of terbacil, halosulfuron, clomazone, and S metolachlor applied pre transplant (PRE) and two rates of halosulfuron applied post transplant (POST). An untreated control was also included. Terbacil was applied at 11 2 and 224 g ai ha 1 halosulfuron was applied at 26 and 39 g ai ha 1 clomazone was applied at 281 and 420 g ai ha 1 and S metolachlor was applied at 1,067 and 1,419 g ai ha 1 Treatments were applied with a CO 2 pressurized sprayer calibrated to deliver 280 L ha 1 For PRE applications, herbicides were applied to the soil surface of fumigated pressed beds. In order to do this, polyethylene mulch used to trap the fumigant was removed, herbicides were applied, and new polyethylene mulch was re applied to the treated bed. For POST applications, herbicide was applied over the top with 0.25% (v/v) nonionic surfactant when the longest vine on each plant was approximately 60 cm in length. Visual estimates of crop injury due to PRE her bicide applications were r ecorded at 17 d ays after transplanting (DAT) Injury was estimated on a scale of 0 to 100% where 0 indicates no injury and 100 indicates crop death. A modified version of the methods used by Dittmar et al. (2008) was used to investi gate halosulfuron POST injury 6 d ays after application ( 25 DAT ). Methods used included: selecting the longest vine on two randomly selected plants per plot, recording the vine length, counting the number of nodes on the last 20 cm of the distal end of the vine, and rating stem splitting on a scale of 0 to 100% where 0 indicates no injury and 100 indicates splitting along the entire length of the vine. Vine length and node counts were taken on all plots regardless of herbicide treatment whereas splitting was only evaluated on p lots treated with halosulfuron POST (only herbicide treatment that resulted in splitting). Vine length

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23 measur ements were also used to evaluate stunting from PRE applications of other herbicides. Watermelons were harvested in 2009 on June 24 (76 DAT ), Jun e 30 (82 DAT), July 7 (89 DAT), and July 14 (96 DAT) and in 2010 on June 21 (76 DAT) and July 6 (91 DAT). The first two harvests in 2009 and the first harvest only in 201 0 were considered early yield. Only marketabl e a analysis Data was analyzed as a randomized complete block design. Analysis of variance was conducted to test for significant treatment effects and interactions (SAS 2003). Arcsine square root transformation of percentage data had results similar to n on transformed data. Therefore, non transformed data was analyzed and presented. Certain injury evaluations had significant treatment by year interaction. Therefore, all data was examined separately by year for comparison purposes. Means were separated Results and Discussion Visual injury from herbicides applied PRE. No visible injury was observed either year with any rootstock in plots treated with PRE applications of terbacil or halosulfuron. Each year, clomazone application resulted in bleaching with all rootstocks (Table 2 1) At both rates, there was no significant difference between rootstocks either year when comparing clomazone blea ching incidence Averaged across rates and rootstocks, clomazone c aused a 32% injury in 2009 and 49% injury in 2010. S metolachlor injury was identified as leaf cupping and crinkling. In 2009, S metolach lor application resulted in minor injury at both rates with means of less than 5% for each rootstock (Table 2 1) C ompared to 2009, S metolachlor caused greater injury at both rates in 2010. However, there was no significant differen ce in herbicide tolerance between rootstocks with injury means ranging from 9 14% across rates and rootstocks Vine length. BG, HS, and NG had shorter vines in 2009 and 2010 with either rate of halosulfuron POST compared to the untreated control (Table 2 2) Each year, both rates o f

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24 clomazone caused shorter vines on HS and NG. C lomazone resulted in significantly shorter vines on BG only at the high rate. NG had shorter vines each year when treated with either rate of S metolachlor. Significantly shorter vines following S metolachlor application were also seen with HS in 2009 (both rates) and with BG in 2010 (high rate only). Stem splitt ing. Halosulfur on POST caused significant stem splitting wit h all rootstocks (Table 2 3 ). In 2009, average stem splitting was 98% or greater on each rootstock at each rate. Essentially, splitting was along the entire length of vines. In 2010, stem spli tting was not as severe. Averaged across rootstocks, the low er rate of halosulfuron caused 71% stem splitt ing and the higher rate caused 75% stem splitting. Node count. BG, HS, and NG had a significant increase in nodes on the last 20 cm of the distal e nd of vines when treat ed with h alosulfuron POST compared to the untreated control (Table 2 4). The increase in nodes occurred each year with both halosulfuron rates. Averaged across rates and rootstocks, halosulfuron POST resulted in 6.1 and 3.5 more nod es in the evaluated area compared to the untreated control in 2009 and 2010, respectively. Other herbicide treatments had similar node counts compared to the untreated control. Yield. Early and total yield expressed at kg per plant and number of fruit pe r plant were examined from 2009 and 2010 (Tables 2 5 and 2 6). In many cases yield was highly variable between plots of the same rootstock and herbicide combination. Therefore, when yield was analyzed for each rootstock, herbicide treatment effect was r arely significant. Early yield of plots treated with clomazone, S metolachlor, and halosulfuron POST tended to have the lo west yields. Fruit size was usually not effected by herbicide treatment (Table 2 7) The only herbicide that caused significantly s maller fruit was halosulfuron in 2009 with NG. However, the mean difference was never greater than 1 kg.

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25 The results of this study indicate that, overall, grafted watermelon responded similarly to nongrafted watermelon in tolerance of terbacil, halosulfur on, clomazone, and S metolachlor or lack thereof. Terbacil and halosulfuron PRE appeared to be safe for use in grafted watermelon. Clomazone and halosulfuron POST resulted in damage to grafted watermelon in a similar manner as non grafted. Minimal visib le injury of grafted and non grafted watermelon to S metolachlor was seen during the fir st year of this study. However, S metolachlor caused greater visual injury the second year and shorter vine lengths both years. This injury was present for both non g rafted and grafted watermelon. The use of S metolachlor in Florida grafted watermelon production should be further examined as it may vary based on environmental factors. Grafting does not impart watermelon tolerance of clomazone or halosulfuron POST. Terbacil and halosulfuron PRE appear to be safe for use in watermelon grafted onto interspecific hybrid squash and bottle gourd.

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26 Table 2 1. Clomazone and S metolachlor injury of non grafted watermelon (NG) and watermelon grafted onto bottle gou rd (BG) and interspecific hybrid squash (HS) at 17 days after transplanting a Injury Rootstock 2009 2010 2009 2010 Clom L b Clom H Clom L Clom H Meto L Meto H Meto L Meto H ------------------------------------------------% -----------------------------------------------BG 16 26 46 46 4 3 10 9 HS 27 39 47 48 1 4 10 13 NG 36 48 46 59 2 4 14 10 LSD 0.05 NS NS NS NS 2 NS NS NS a b Abbreviations: Clom, clomazone; Meto, S metolachlor; L, low rate; H, high rate ; NS, not significant

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27 Table 2 2 Effect of herbicide treatments on vine length of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootst ocks at 25 days after transplanting a Vine length Herbicide Rate Timing b BG HS NG 2009 g ai ha 1 ----------------cm -----------------Terbacil 112 PRE 113 136 123 Terbacil 224 PRE 121 122 109 Halosulfuron 26 PRE 125 133 109 Halosulfuron 39 PRE 139 123 126 Halosulfuron 26 POST 66 79 66 Halosulfuron 39 POST 76 88 71 Clomazone 281 PRE 113 102 86 Clomazone 420 PRE 92 90 72 S metolachlor 1,067 PRE 102 109 85 S metolachlor 1,419 PRE 101 116 87 Untreated 117 145 117 LSD 0.05 21 26 20 2010 Terbacil 112 PRE 89 103 84 Terbacil 224 PRE 93 107 97 Hal osulfuron 26 PRE 90 78 80 Halosulfuron 39 PRE 90 82 88 Halosulfuron 26 POST 62 64 60 Halosulfuron 39 POST 62 62 62 Clomazone 281 PRE 80 57 64 Clomazone 420 PRE 62 59 61 S metolachlor 1,067 PRE 75 81 64 S metolachlor 1,419 PR E 61 68 53 Untreated 89 99 98 LSD 0.05 24 32 31 a b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; P OST, post transplant.

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28 Table 2 3 Stem splitting from halosulfuron POST application to non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) at 6 days after application a Stem s plitting Rootsto ck 2009 2010 26 g ai ha 1 39 g ai ha 1 26 g ai ha 1 39 g ai ha 1 -----------------------------------------% -----------------------------------------BG 99 100 60 63 HS 98 98 75 73 NG 99 99 78 89 LSD 0.05 NS 1 NS NS a Least significant differences All treatments included a 0.25% nonio nic surfactant. Abbreviations: POST, post transplant ; NS, not significant

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29 Table 2 4 Effect of herbicide treatment on node co unt of the last 20 cm of the distal end of vines from non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootst ocks at 25 days after transplanting a Nodes Herbicide Rate Timing b BG HS NG 20 09 g ai ha 1 -----------------No. -----------------Terbacil 112 PRE 5.6 5.3 5.5 Terbacil 224 PRE 5.5 5.6 5.8 Halosulfuron 26 PRE 6.1 6.3 6.1 Halosulfuron 39 PRE 5.6 5.8 5.9 Halosulfuron 26 POST 11.8 11.8 11.6 Halosulfuron 39 POS T 12.6 11.4 12.1 Clomazone 281 PRE 5.5 5.6 5.6 Clomazone 420 PRE 5.8 6.1 5.4 S metolachlor 1,067 PRE 6.0 5.8 5.8 S metolachlor 1,419 PRE 5.8 5.6 5.9 Untreated 5.6 6.1 5.8 LSD 0.05 0.9 1.0 0.8 2010 Terbacil 112 PRE 5.5 5.4 5.8 Terbacil 224 PRE 5.3 5.4 5.5 Halosulfuron 26 PRE 5.6 5.4 5.9 Halosulfuron 39 PRE 5.4 5.5 5.5 Halosulfuron 26 POST 8.3 8.8 8.9 Halosulfuron 39 POST 9.6 9.9 9.9 Clomazone 281 PRE 5.3 6.0 6.3 Clomazone 420 PRE 5.4 6.1 6.3 S metolachlor 1,067 PRE 5.6 5.3 6.0 S metolachlor 1,419 PRE 5.5 5.5 6.1 Untreated 5.6 5.9 5.8 LSD 0.05 0.9 0.8 1.1 a b All treatments applied POST i ncluded a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transplant.

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30 Table 2 5. Effect of herbicide treatment on e arly and total yield of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and intersp ecific hybrid squash ( HS) rootstocks expressed as kg per plant. a Early y ield Total y ield Herbicide Rate Timing b BG HS NG BG HS NG 2009 g ai ha 1 ------------------------kg/plant ------------------------Terbacil 112 PRE 17.5 16.7 17.5 24.7 21.2 23.4 Terbacil 224 PRE 17.7 19.4 17.1 25.3 22.9 23.8 Halosulfuron 26 PRE 18.5 18.2 16.6 27.7 24.9 21.3 Halosulfuron 39 PRE 16.7 16.2 18.5 23.3 20.3 23.7 Halosulfuron 26 POST 11.6 13.3 15.8 18.8 19.9 22.5 Halosulfuron 39 POST 12.7 14.4 14.9 21.6 27.3 22.7 Clomazone 281 PRE 14.8 12.0 14.9 20.6 19.2 22.5 Clomazone 420 PRE 19.9 14.9 13.6 25.3 20.1 21.2 S metolachlor 1,067 PRE 12.6 10.2 12.5 20.4 17.4 18.6 S metolachlor 1,419 PRE 15.2 12.1 15.5 21.6 15.4 27.4 U ntreated 16.5 20.2 19.9 19.6 24.2 25.9 LSD 0.05 NS NS 4.1 NS 6.2 NS 2010 Terbacil 112 PRE 18.2 13.8 14.8 21.9 17.9 19.7 Terbacil 224 PRE 18.1 13.7 19.0 20.9 17.7 20.5 Halosulfuron 26 PRE 16.1 15.8 20.3 23.1 19.8 22.0 Halosulfur on 39 PRE 20.7 12.3 20.0 26.6 17.6 23.3 Halosulfuron 26 POST 22.1 13.0 15.5 25.2 20.6 20.5 Halosulfuron 39 POST 20.1 10.0 13.7 23.7 15.3 19.0 Clomazone 281 PRE 19.0 10.2 15.0 26.2 17.1 21.1 Clomazone 420 PRE 17.0 14.1 18.4 23.9 16.3 20. 5 S metolachlor 1,067 PRE 15.9 14.8 21.0 20.2 20.8 23.6 S metolachlor 1,419 PRE 13.4 10.6 22.8 16.2 15.4 27.3 Untreated 19.0 16.6 23.0 23.3 19.9 26.0 LSD 0.05 NS NS NS NS NS NS a it. Least significant differences were b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transplant ; NS, not significant

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31 Tabl e 2 6. Effect of herbicide treatment on e arly and total yield of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash ( HS) rootstocks expressed as number of fruit per plant. a Early y ield Total y ield Herbicide Rate Timing b BG HS NG BG HS NG 2009 g ai ha 1 ------------------------no/plant ------------------------Terbacil 112 PRE 2.2 1.8 2.3 3.3 2.5 3.2 Terbacil 224 PRE 2.3 2.7 2.2 3.4 3.1 3.2 Halosulfuron 26 PRE 2.4 2.2 2 .3 3.9 3.1 3.0 Halosulfuron 39 PRE 2.0 2.2 2.4 3.0 2.8 3.1 Halosulfuron 26 POST 1.7 1.8 2.2 2.8 2.8 3.2 Halosulfuron 39 POST 1.9 2.1 2.2 3.3 4.1 3.4 Clomazone 281 PRE 1.8 1.6 2.0 2.7 2.6 3.1 Clomazone 420 PRE 2.7 2.0 1.8 3.4 2.8 3.0 S metolachlor 1,067 PRE 1.7 1.3 1.8 3.0 2.5 2.6 S metolachlor 1,419 PRE 1.9 1.7 2.0 3.0 2.2 3.5 Untreated 2.3 2.7 2.5 2.8 3.3 3.4 LSD 0.05 NS NS NS NS 0.8 NS 2010 Terbacil 112 PRE 2.4 1.9 2.0 2.9 2.5 2.7 Terbacil 224 PRE 2. 3 1.9 2.4 2.8 2.5 2.7 Halosulfuron 26 PRE 2.0 1.8 2.5 2.9 2.5 2.8 Halosulfuron 39 PRE 2.7 1.7 2.4 3.5 2.5 2.8 Halosulfuron 26 POST 2.8 1.8 2.2 3.3 2.8 2.8 Halosulfuron 39 POST 2.5 1.3 1.9 3.0 2.1 2.6 Clomazone 281 PRE 2.3 1.4 1.8 3.1 2.3 2.6 Clomazone 420 PRE 2.0 1.8 2.3 3.0 2.1 2.6 S metolachlor 1,067 PRE 2.0 1.8 2.5 2.6 2.6 2.9 S metolachlor 1,419 PRE 1.7 1.4 2.7 2.1 2.0 3.2 Untreated 2.5 2.1 2.9 3.1 2.6 3.3 LSD 0.05 NS NS NS NS NS NS a Early and total yield onl b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transpla nt ; NS, not significant

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32 Table 2 7. Effect of herbicide treatment on f ruit size of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks. a Fruit size Herbicide Rate Timing b BG H S NG 2009 g ai ha 1 -----------------kg/fruit -----------------Terbacil 112 PRE 7.4 8.5 7.4 Terbacil 224 PRE 7.4 7.4 7.4 Halosulfuron 26 PRE 7.1 8.2 7.1 Halosulfuron 39 PRE 7.8 7.2 7.7 Halosulfuron 26 POST 6.8 7.2 7.1 Halosulfur on 39 POST 6.6 6.7 6.7 Clomazone 281 PRE 7.6 7.3 7.3 Clomazone 420 PRE 7.4 7.1 7.2 S metolachlor 1,067 PRE 6.8 7.0 7.3 S metolachlor 1,419 PRE 7.4 7.1 7.7 Untreated 7.1 7.4 7.7 LSD 0.05 0.7 NS 0.6 2010 Terbacil 112 PRE 7 .6 7.1 7.3 Terbacil 224 PRE 7.5 6.9 7.6 Halosulfuron 26 PRE 8.1 8.0 7.9 Halosulfuron 39 PRE 7.7 7.1 8.2 Halosulfuron 26 POST 7.8 7.4 7.4 Halosulfuron 39 POST 8.1 7.2 7.3 Clomazone 281 PRE 8.5 7.6 8.2 Clomazone 420 PRE 8.3 7.8 7.8 S metolachlor 1,067 PRE 7.8 8.1 8.1 S metolachlor 1,419 PRE 7.7 7.5 8.6 Untreated 7.6 7.7 8.0 LSD 0.05 NS NS NS a b All treatments applied POS T included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transplant ; NS, not significant

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33 CHAPTER 3 TERBACIL, HALOSULFURON, CLOMAZONE, AND S METOLACHLOR EFFECT ON GRAFTED T RIPLOID WATERMELON IN SOUTH CAROLINA Objective Herbicide tolerance of grafted watermelon [ Citrullus lanatus (Thunb.) Matsumura and Nakai] is widely unknown. The objective of this research was to examine the impact of terbacil, halosulfuron, clomazone, and S metolachlor on injury and yield of grafted t riplo id watermelon in South Carolina. Materials and Methods Field experiments were conducted at the Clemson University Coastal Research and Education Center, Charleston, SC (CREC ) in the spring of 2009 and 2010. Soil type at the CREC is a Yauhmal fine loa my sand (Aquic Hapludilts) with less than 2% organic matter and pH 6.1. Raised be ds used in the experiment were 0.76 m wide and established on 2.44 m center s. Prior to transplanting, beds were fumigated with methyl bromide and chloropicrin (98:2) at 269 kg ha 1 and covered with black polyethylene mulch. Experimental design was a split plot with four replications. Main plot factor was herbicide all grafting com ) [ Lagenaria siceraria (Mol.) Standl.] ( Cucurbita maxima x C. moschata ) and non co nducted using splice grafts. On April 21, 2009 and April 20, 2010, transplants were established at an in row spacing of 0.91 m. To provide viable pollen for fruit set, diploid pollenizers were transplanted in row at a 1:3 (pollenizer to triploid) ratio. All transplants were provided by Syngenta Full Count TM Plant Program, Naples, FL. Plots were irrigated via drip tape that was placed under the polyethylene mulch.

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34 Herbicide treatments included two rates of terbacil, halosulfuron, clomazone, and S metolac hlor applied pre transplant (PRE) and two rates of halosulfuron applied post transplant (POST). An untreated control was also included. Terbacil was applied at 112 and 224 g ai ha 1 halosulfuron was applied at 26 and 39 g ai ha 1 clomazone was applied at 281 and 420 g ai ha 1 and S metolachlor was applied at 1,067 and 1,419 g ai ha 1 Treatments were applied with a CO 2 pressurized sprayer. For PRE applications, herbicides were applied to the soil surface of fumigated pressed beds. In order to do thi s, polyethylene mulch used to trap the fumigant was removed, herbicides were applied, and new polyethylene mulch was re applied to the treated bed. For POST applications, herbicide was applied over the top with 0.25% (v/v) nonionic surfactan t at 21 days a fter transplanting (DAT) Visual estimates of crop injury due to PRE herbicide ap p lications were taken at 20 DAT in 2009. Injury was estimated on a scale of 0 10 where 0 indicates no injury and 10 indicates crop death. On the same date in 2009 the lengt h of the longest vine of two randomly selected plants per plot was recorded. In 2010, plots treated with halosulfuron POST were evaluated using a similar 0 10 scale at 9 days after application (31 DAT) Watermelons were harvested in 2009 on July 7 (77 DA T ), July 20 (90 DAT), and July 29 (99 DAT) and in 2010 on July 2 (73 DAT), July 12 (83 DAT), and July 21 (92 DAT). The first harvest in 2009 and the first two harvests in 2010 were considered early yield. were included in data analysis. Since different injury evaluations were conducted in 2009 and 2010, yield was analyzed separately each year for comparison purposes. Data was analyzed as a randomized complete block design. Analysis of variance was conducted to test for significant treatment effects (SAS

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35 Results and Discussion Injury Evaluations Clomazone was the only PRE applied herbicide that re sulted in visible injury at 20 DAT (Table 3 1) At the low clomazone rate, HS exhibited significantly greater clomazone injury compared to BG and NG. At the high rate, each rootstock had similar injury. None of the rootstocks had significantly different vine lengths based on PRE herbicide treatment (Table 3 2) Halosulfuron POST did not cause extensive injury in 2009. In 2010, halosulfuron POST resulted in similar injury for each rootstock (Table 3 3) Yield. When examining early or total marketable yield expressed as kg per plant, none of the herbicide treatments resulted in significantly lower yield compared to the untreated control (Table 3 4) When examining the early or total marketable yield expressed as number of fruit per plant, the only sig nificant difference in yield based on herbicide treatment was in 2009 with NG (Table 3 5) NG had significantly less early marketable fruit harvested per plant following the high rate of halosulfuron POST and the high rate of S metolachlor. There were no significant differences in fruit si ze based on herbicide treatment (Table 3 6). Ter bacil and halosulfuron PRE appear to be safe for use in South Carolina grafted watermelon production. At the high rate of clomazone, each rootstock had similar injury. Al though limited halosulfuron POST injury occurred in 2009, plants on all rootstocks were damaged in 2010. No visible injury or stunting was reported from S metolachlor application. Herbicides treatments had no consistent impact on yield.

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36 Table 3 1. Cl omazone injury of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks at 20 days after transplanting in 2009 a Injury Rootstock 281 g ai ha 1 420 g ai ha 1 --------------------0 10 ------------------BG 0.75 2.25 HS 2.50 2.75 NG 0.25 2.00 LSD 0.05 1.36 NS a Least significant differences we Abbreviation: NS, not significant

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37 Table 3 2 Effect of herbicide treatments on vine length of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and inter specific hy brid squash (HS) rootstocks at 20 days after transplanting in 2009. a Vine length Herbicide Rate Timing b BG HS NG g ai ha 1 ------------------cm -----------------Terbacil 112 PRE 89 117 112 Terbacil 224 PRE 88 115 108 Halosulfur on 26 PRE 101 98 106 Halosulfuron 39 PRE 99 102 101 Clomazone 281 PRE 98 95 108 Clomazone 420 PRE 98 104 103 S metolachlor 1,067 PRE 88 102 100 S metolachlor 1,419 PRE 96 95 98 Untreated 106 120 110 LSD 0.05 NS NS NS a Least significant d b Abbreviation s : PRE, pre transplant ; NS, not significant

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38 Table 3 3. Halosulfuron POST injury of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG ) and interspecific hybrid squash (HS) rootstocks at 9 days after application in 2010 a Injury Rootstock 26 g ai ha 1 39 g ai ha 1 --------------------0 10 -------------------BG 2.75 5.25 HS 3.25 6.25 NG 2.50 6.25 LSD 0.05 NS NS a Least significan treatments included a 0.25% nonio nic surfactant. Abbreviations: POST, post transplant; NS, not significant.

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39 Table 3 4. Effect of herbicide treatment on e arly and total yield of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks expressed at kg per plant. a Early y ield Total y ield Herbicide Rate Timing b BG HS NG BG HS NG 2009 g ai ha 1 ------------------------kg/pla nt ------------------------Terbacil 112 PRE 15.8 12.8 16.9 19.8 15.2 21.1 Terbacil 224 PRE 13.1 17.7 15.1 19.3 21.6 21.5 Halosulfuron 26 PRE 19.4 16.3 13.1 27.4 19.7 18.0 Halosulfuron 39 PRE 13.7 18.0 19.3 17.0 23.9 21.7 Halosulfuron 2 6 POST 16.5 14.9 13.9 20.8 20.8 21.4 Halosulfuron 39 POST 16.3 15.5 13.3 22.0 20.6 23.7 Clomazone 281 PRE 18.0 17.9 14.0 22.9 22.0 20.1 Clomazone 420 PRE 14.8 14.8 18.8 22.8 21.1 23.9 S metolachlor 1,067 PRE 21.1 19.0 16.8 29.8 21.2 21.6 S metolachlor 1,419 PRE 18.4 12.4 10.9 25.9 20.8 19.8 Untreated 11.5 14.6 16.5 20.5 20.8 21.9 LSD 0.05 NS NS NS 5.8 NS NS 2010 Terbacil 112 PRE 15.1 18.4 17.4 18.4 21.1 19.5 Terbacil 224 PRE 17.7 20.8 21.5 20.7 27.6 26.3 Hal osulfuron 26 PRE 18.3 15.4 20.9 20.4 18.5 23.2 Halosulfuron 39 PRE 12.6 13.8 18.6 16.3 18.1 21.4 Halosulfuron 26 POST 18.3 14.4 17.3 21.5 16.0 20.9 Halosulfuron 39 POST 18.4 15.9 18.0 22.7 18.7 21.5 Clomazone 281 PRE 14.8 17.8 15.7 16.9 19.6 17.6 Clomazone 420 PRE 17.0 16.9 20.4 20.1 19.1 21.8 S metolachlor 1,067 PRE 18.4 18.8 21.1 21.8 22.8 25.0 S metolachlor 1,419 PRE 15.1 15.9 17.4 18.4 18.9 22.7 Untreated 18.2 19.3 20.3 23.3 21.4 22.4 LSD 0.05 NA NS NS NS NS NS a b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre trans plant; POST, post transplant ; NS, not significant

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40 Table 3 5. E ffect of herbicide treatment on e arly and total yield of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstock expresse d as number of fruit per plant. a Early y ield Total y ield Herbicide Rate Timing b BG HS NG BG HS NG 2009 g ai ha 1 ------------------------no/plant ------------------------Terbacil 112 PRE 2.3 1.8 2.4 2.9 2.2 3.2 Terbacil 224 PRE 2.1 2.3 2.3 3 .0 3.0 3.3 Halosulfuron 26 PRE 2.8 2.4 1.9 4.1 2.9 2.7 Halosulfuron 39 PRE 2.0 2.2 2.6 2.6 3.1 3.0 Halosulfuron 26 POST 2.4 2.3 1.9 3.0 3.0 2.9 Halosulfuron 39 POST 2.3 2.3 1.7 3.2 2.9 3.0 Clomazone 281 PRE 2.9 2.6 1.8 3.7 3.3 2.8 Clomazone 420 PRE 2.1 2.1 2.5 3.3 3.1 3.3 S metolachlor 1,067 PRE 2.9 2.7 2.4 4.2 3.0 3.1 S metolachlor 1,419 PRE 2.8 1.8 1.5 3.9 2.9 2.8 Untreated 1.8 2.1 2.4 3.3 2.9 3.2 LSD 0.05 NS NS 0.7 0.8 NS NS 2010 Terbacil 112 PRE 2. 2 2.3 2.3 2.6 2.8 2.7 Terbacil 224 PRE 2.4 2.7 2.7 2.9 3.6 3.4 Halosulfuron 26 PRE 2.4 2.0 2.5 2.8 2.5 2.9 Halosulfuron 39 PRE 1.6 1.9 2.3 2.4 2.5 2.8 Halosulfuron 26 POST 2.5 2.0 2.3 3.0 2.3 2.8 Halosulfuron 39 POST 2.5 2.2 2.5 3.2 2 .7 3.0 Clomazone 281 PRE 2.0 2.3 2.1 2.5 2.6 2.4 Clomazone 420 PRE 2.4 2.1 2.6 2.9 2.5 2.9 S metolachlor 1,067 PRE 2.3 2.5 2.6 2.9 3.1 3.3 S metolachlor 1,419 PRE 2.0 2.0 2.4 2.5 2.5 3.2 Untreated 2.4 2.7 2.7 3.2 3.0 3.0 LSD 0.05 NS NS NS NS NS NS a b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviati ons: PRE, pre transplant; POST, post transplant ; NS, not significant

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41 Table 3 6. Effect of herbicide treatment on f ruit size of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks. a Fruit size Herbicide Rate Timing b BG HS NG 2009 g ai ha 1 -----------------kg/fruit -----------------Terbacil 112 PRE 6.8 6.8 6.6 Terbacil 224 PRE 6.5 7.3 6.6 Halosulfuron 26 PRE 6.8 6.8 6.7 Halosulfuron 39 PRE 6.6 7.7 7.3 Ha losulfuron 26 POST 6.9 6.9 7.4 Halosulfuron 39 POST 7.0 7.1 7.9 Clomazone 281 PRE 6.3 6.7 7.3 Clomazone 420 PRE 6.8 7.0 7.3 S metolachlor 1,067 PRE 7.2 7.0 7.0 S metolachlor 1,419 PRE 6.7 7.0 7.0 Untreated 6.1 7.2 6.8 LSD 0.05 NS NS NS 2010 Terbacil 112 PRE 7.1 7.7 7.2 Terbacil 224 PRE 7.1 7.7 7.8 Halosulfuron 26 PRE 7.2 7.3 8.0 Halosulfuron 39 PRE 6.9 7.2 7.7 Halosulfuron 26 POST 7.0 7.0 7.5 Halosulfuron 39 POST 7.2 7.1 7.0 Clomazone 281 P RE 6.9 7.7 7.3 Clomazone 420 PRE 6.9 7.7 7.5 S metolachlor 1,067 PRE 7.6 7.3 7.5 S metolachlor 1,419 PRE 7.4 7.5 7.1 Untreated 7.4 7.2 7.5 LSD 0.05 NS NS NS a est b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transplant ; NS, not significant

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42 CHAPTER 4 TERBACIL, HALOSULFUR ON, CLOMAZONE, AND S METOLACHLOR EFFECT O N GRAFTED TRIPLOID WATERMELON IN NORTH CAROLINA Objective Herbicide tolerance of grafted watermelon [ Citrullus lanatus (Thunb.) Matsumura and Nakai] is widely unknown. The objective of this research was to examine the impact of terbacil, halosulfuron, clomazone, and S meto lachlor on yield of grafte d triploid watermelon in North Carolina. Materials and Methods Field experiments were conducted at the North Carolina State University Cunningham Research Station, Kinston, NC (CRS) in the spring of 2010. Soil type at the CRS is a Norfolk sandy loam with a cation exchange capacity of 3.6, 0.56% organic matter, and pH 5.5. Raised beds used in the experiment were 0.91 m wide and established on 3.05 m centers. All fertilizer was a pplied according to the Vegetable Crop Handbook for Southeastern United States ( Kemble 2010) Prior to transplanting, beds were fumigated with methyl bromide and chloropicrin (98:2) at 269 kg ha 1 and covered with black polyethylene mulch. Experimental design was a split plot with four replications. Main plot factor was herbicide ) [ Lagenaria siceraria (Mol.) Standl.] specific hybrid squash (HS) ( Cucurbita maxima x C. moschata ) and non conducted using s plice grafts. Watermelon transplants were esta blished on May 12, 2010 To provide viable pollen for f ruit set, diploid pollenizers w ere transplanted in row at a 1:2 (pollenizer to triploid) ratio. All transplants were provided by Syngenta Full Count TM Plant

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43 Program Naples, FL. Plots were irrigated via drip tape that was placed under the polyethylene mu lch. Herbicide treatments included two rates of terbacil, halosulfuron, clomazone, and S metolachlor applied pre transplant (PRE) and two rates of halosulfuron applied post transplant (POST). An untreated control was also included. Terbacil was applied a t 112 and 224 g ai ha 1 halosulfuron was applied at 26 and 39 g ai ha 1 clomazone was applied at 281 and 420 g ai ha 1 and S metolachlor was applied at 1,067 and 1,419 g ai ha 1 Treatments were applied with a CO 2 pressurized sprayer. For PRE applicat ions, herbicides were applied to the soil surface of fumigated pressed beds. In order to do this, polyethylene mulch used to trap the fumigant was removed, herbicides were applied, and new polyethylene mulch was re applied to the treated bed. For POST ap plications, herbicide was applied over the top with 0.25% (v/v) nonionic surfactant at 26 days after transplanting Watermelons were harvested three times. The first two harvests were considered early yield. Only marketable fruit ( 4.5 kg) were consider ed in data analysis. Data was analyzed as a randomized complete block design. Analysis of variance was conducted to test for significant 0.05. Results and Discus sion Non grafted plants exhibited greater yield in general compared to grafted plants (Table 4 1 and 4 2 ) There was no significant difference in total marketable yield based on herbicide treatment. NG had significantly lower early marketable yield with the high rate of clomazone and with both rates of halosulfuron POST (Table 4 1) There were no significant differences in fruit size based on herbicide treatment.

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44 Terbacil, S metolachlor, and halosulfuron PRE did not result in significantly lower early or total yield compared to the untreated control. Early yield was significantly reduced for NG with clomazone and halosulfuron POST. Although certain herbicide treatments had lower yield on grafted plants, none of the differences were significant. V is ual injury of non grafted watermelon and watermelon grafted onto bottle gourd and interspecific hybrid squash with PRE application of halosulfuron clomazone, and S metolachlor and POST application of halosulfuron has been documented in North Carolina ( P. J. Dittmar, unpublished data). Further research is needed in North Carolina to make conclusions about herbicide tolerance of grafted watermelon in the state. Although halosulfuron PRE was considered safe in Florida and S outh Carolina, it may not be in ce rtain North Carolina growing conditions.

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45 Table 4 1 Effect of herbicide treatment on e arly and total yield of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks expressed as kg per plant. a Early y ield Total y ield Herbicide Rate Timing b BG HS NG BG HS NG g ai ha 1 ------------------------kg/plant ------------------------Terbacil 112 PRE 13.9 12.7 20.6 22.7 18.4 32.8 Terbacil 224 PRE 19.2 14.4 22.5 27.9 23.6 35.7 H alosulfuron 26 PRE 14.8 14.5 21.3 22.7 21.2 31.3 Halosulfuron 39 PRE 15.8 16.4 21.9 21.9 24.6 28.7 Halosulfuron 26 POST 13.0 15.6 18.8 22.1 24.5 30.5 Halosulfuron 39 POST 10.5 13.3 14.1 25.8 24.7 22.7 Clomazone 281 PRE 17.7 14.3 20.8 22.9 23.2 32.5 Clomazone 420 PRE 16.7 11.4 13.9 25.4 20.1 28.4 S metolachlor 1,067 PRE 14.8 15.6 20.9 20.7 23.7 34.0 S metolachlor 1,419 PRE 15.3 12.6 20.0 20.2 19.4 27.1 Untreated 18.2 16.4 25.2 24.4 22.7 32.1 LSD 0.05 NS NS 6.4 NS NS NS a Early and tota l yiel b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post tra nsplant ; NS, not significant

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46 Table 4 2. E ffect of herbicide treatment on e arly and total yield of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks expressed as number of f ruit per plant. a Early y ield Total y ield Herbicide Rate Timing b BG HS NG BG HS NG g ai ha 1 ------------------------no/plant ------------------------Terbacil 112 PRE 2.1 1.8 2.6 3.4 2.6 4.3 Terbacil 224 PRE 2.7 2.1 3.1 4.0 3.5 5.1 H alosulfuron 26 PRE 2.3 2.1 3.0 3.5 3.1 4.6 Halosulfuron 39 PRE 2.3 2.4 2.9 3.3 3.6 3.9 Halosulfuron 26 POST 2.0 2.2 2.7 3.4 3.6 4.3 Halosulfuron 39 POST 1.5 2.0 1.9 3.7 3.8 3.3 Clomazone 281 PRE 2.7 2.1 2.8 3.5 3.4 4.5 Clomazone 420 PRE 2.4 1 .7 1.9 3.6 3.0 3.9 S metolachlor 1,067 PRE 2.2 2.2 2.6 3.2 3.4 4.6 S metolachlor 1,419 PRE 2.2 1.8 2.7 2.9 2.9 3.8 Untreated 2.7 2.4 3.3 3.8 3.3 4.4 LSD 0.05 NS NS 0.8 NS NS NS a Early and total yield only include marketable ( b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transplant ; NS, not significan t

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47 Table 4 3 Effect of herbicide treatment on f ruit size of non grafted watermelon (NG) and watermelon grafted onto bottle gourd (BG) and interspecific hybrid squash (HS) rootstocks. a Fruit size Herbicide Rate Timing b BG HS NG g ai ha 1 -----------------kg/fruit -----------------Terbacil 112 PRE 6.6 7.0 7.7 Terbacil 224 PRE 7.0 6.8 7.0 Halosulfuron 26 PRE 6.5 7.0 6.8 Halosulfuron 39 PRE 6.7 6.8 7.4 Halosulfuron 26 POST 6.5 6.9 7.1 Halosulfuron 39 POST 6.9 6.5 6. 8 Clomazone 281 PRE 6.5 6.7 7.3 Clomazone 420 PRE 7.2 6.4 7.1 S metolachlor 1,067 PRE 6.4 7.1 7.6 S metolachlor 1,419 PRE 6.9 6.7 7.2 Untreated 6.5 6.7 7.4 LSD 0.05 NS NS NS a cted LSD test b All treatments applied POST included a 0.25% nonionic surfactant. Abbreviations: PRE, pre transplant; POST, post transplant ; NS, not significant

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48 CHAPTER 5 HERBICIDE UPTAKE AND TRANSLOCATION IN GRAFTED TRIPLOID WATERMELON Objective Informa tion regarding the impact of grafting on herbicide uptake and translocation in watermelon may further explain herbicide tolerance of grafted watermelon [ Citrullus lanatus (Thunb.) Matsumura and Nakai]. The objective of this research was to determine herbi cide uptake and translocation characteristics of grafted watermelon using two radioisotope based techniques: liquid scintillation spectrometry and autoradiography Materials and Methods Plant Material 1 was used as a sc ion in all grafting combinations. 1 [ Lagenaria siceraria (Mol.) Standl.] 1 ( Cucurbita maxima x C. moschata ) X on (NON). Grafting was conducting using the one cotyledon m ethod described by Hassell (2008 ). Graft unions were healed in a n environmentally controlled chamber with high humidity and low light conditions for one week. Humidity was gradually reduced and light intensity was gradually increased during the later portion of the week. Following an additional week of growth in a greenhouse, plants were at a stage where they would normally be ready for field transpl anting. At that time, plants were instead transplanted into small pots 2 (515 ml volume) of sand 3 to allow for one more week of growth in the greenhouse At 21 days after grafting, plants were at the desired stage (5 true leaves) for herbicide treatment.

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49 Herbicide Treatment Herbicide uptake and translocation were examined using soil applied 14 C atrazine and foliar applied 14 C glyphos ate Atrazine was applied at 658 g ai ha 1 in a 5 ml soil drench placed directly onto the root ball with a pipette. Includ ed in the 5 ml drench was 6.67 kBq of 14 C atrazine. G lyphosate (non radiolabeled) was oversprayed at 842 g ae ha 1 using a CO 2 pressur ized sprayer with a single flat fan nozzle A 5 l drop containing 6.67 kBq of 14 C glyphosate was applied to a marked ci rcle (~1.5 cm diameter) on the adaxial surface of a fully expanded leaf on each plant using a pipette. Treatments were applied on April 19 (trial 1) and July 12 (trial 2) 2010. Plants were kept in a greenhouse in Gainesville, FL during and subsequent to herbicide treatment and exposed to a natural photoperiod. Temperatures were Harvest Plant harvests occurred at 24 a nd 72 hours after treatment (HAT ). At each harvest, leaves treated with 14 C glyphosate were excised and rinsed with five sequen tial 1 ml applications of deionized water. Leaf rinse was directed at the circle where treatment occurred. Leaf rinsate was collected for each treated leaf for s ubsequent scintillation counting Roots of glyphosate and atrazine treated plants were rinse d in a solution of water, sodium hexametaphosphate, and s odium carbonate to remove planting media. Each plant was separated into roots and shoots with a utility knife to prevent further herbicide translocation from one part to another. Grafted plants wer e separated at the graft union. Non grafted plants were separated between the cotyledons and the r oots. Plants were hours.

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50 Autoradiography O ne dried plant was selected from each trea tment and placed on X ray film 4 Films were placed in X ray folders and kept in the dark at room temperature for a 40 day exposure period. Following the exposure period, plants were removed from the X ray folders and autoradiographs were created by devel oping the film The intensi ty of each image was examined visually to estimate the amount of radiolabeled herbicide present. Liquid Scintillation Spectrometry Individual parts of each plant, including those prev iously used for autoradiographs, were finely ground through a 20 mesh screen using a grinding mill 5 Weights of each root, shoot, and treated leaf (glyphosate treatments only) were recorded prior to grinding. A subsample of each plant part weighing approximately 0.2 g (if available) was placed into a ceramic combustion boat. Exact weights of each subsample were recorded. Ground plant tissue was oxidized at 900 C in an automated oxidizer 6 Evolved 14 CO 2 was trapped in 20 ml of liquid scintillation cocktail 7 Vials containing the cocktail were placed i n a liquid scintillation analyzer 8 to quantify the radioactivity [ disintegrations per minute (DPM)] of each su bsample. DPM values of each subsample were adjusted to the weight of the original sample. Herbicide uptake was defined as the total absorbed 14 C kBq (converted from DPM value) obtained from all plant parts expressed as the percentage of applied 14 C kBq f or each treatment Herb icide translocation was defined as the total 14 C kBq obtained in a particular plant part expressed as the percentage of the total absorbed 14 C kBq obtained from all plant parts for each treatment. Experimental Design and Data Analys is All treatments were assigned in a completely randomized design with five replications and the entire study was repeated. Trial 1 and trial 2 were exami ned separately due to rootstock by

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51 trial interaction. Data was subjected to analysis of variance 9 an d means were separated using Results and Discussion Autoradiography All rootstocks produced similar atrazine distribution patterns when examining autoradiographs from trial 1 and trial 2 (Figures 5 1 and 5 2). At 24 HAT, atrazine already reached the entire shoot of plants for each rootstock. This was evident based on the visibility of the entire plant on the X ray films. At 72 HAT, further accumulation of atrazine at the leaf margins is visible. Glyphosate distribution patterns were less consistent compared to atrazine. This was especially the case in trial 1 (Figure 5 3). In trial 2, similar distribution of glyphosate is apparent at 24 and 72 HAT when comparing between BG, HS, and SELF (Figure 5 4). At 72 HAT, glyphosate distribution in NON is al so similar to the other three rootstocks. Liquid Scintillation Spectrometry Uptake At 72 HAT, atrazine uptake was less than 30% of the total applied for all rootst ocks in either trial (Tables 5 2 and 5 3 ). BG, SELF, and NON absorbed a similar amount of herbicide in both trials. HS exhibited greater uptake compared to all other rootstocks at 24 and 72 HAT in trial 1 and at 72 HAT in trial 2. No significant difference in glyphosate uptake was seen in either trail when comparing the four rootstocks ( Tables 5 4 and 5 5 ). Averaged across rootstocks, glyphosate uptake was 89% and 70% of the total applied at 72 HAT in trial 1 and trial 2, respectively. There was also no significant difference in glyphosate absorption based on leaf rinsates when comparing the four rootstocks.

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52 Liquid Scintillation Spectrometry Translocation By 24 HAT, most of the absorbed atrazine passed through the roots and into the sho ots for all rootstocks in both trial s (Table 5 2 and 5 3 ). A higher percentage of absorbed atrazine was found in the shoot of NON compared to BG and HS at 24 and 72 HAT in trial 1 and at 24 HAT in trial 2. SELF had a higher percentage of absorbed atrazine in the shoot compared to BG at each harvest in both trials. Although some differences were statistical ly significant, none of the rootstocks had greater than an 11% difference in the percentage of absorbed atrazine found in the shoot at 72 HAT when comparing between rootstocks in either trial. Regardless of rootstock, greater than 75% of the absorbed glyph osate remained in the treated leaf through 7 2 HAT in both trials (Tables 5 4 and 5 5 ). Only a small percentage of absorbed glyphosate reached the roots at either harvest. No significant difference was observed among the rootstocks in either trial when co mparing the percentage of absorbed glyphosate found in roots, shoots, or treated leaves. There were no significant differences in glyphosate uptake or translocation based on rootstock when examining results from liquid scintillation spectrometry. Further more, any differences in glyphosate distribution observed in autoradiographs were not consistent across harvest times or trials. Differences were observed when comparing the percent of absorbed atrazine found in the roots and shoots based on rootstock. O verall, NON and SELF had a higher percentage of absorbed atrazine reach the sho ot compared to BG and HS. Since SELF also had a higher percentage, this would infer that any impact of the graft per se was not likely the cause of differential translocation. Furthermore, differences based on the rootstock material may have a more direct impact. From a biological standpoint, most of the differences in the distribution of absorbed atrazine were likely so small (although statistically significant) that the actu al differences in the amount of herbicide found in each plant portion would have a minimal impact

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53 on herbicide tolerance The greater quantity of atrazine taken up by ST would probably cause a much greater herbicide response. The greater uptake by ST com pared to SEL F and NON may be due to the greater root mass of ST (Tables 5 6 and 5 7 ) However, BG had an even greater root mass than ST in t rial 1 without a corresponding increase in herbicide uptake. This study revealed minor differences in translocation of absorbed atrazine based on rootstock. However, differences were not as drastic in comparison to that seen in cucumber and squash by Baker and Warren (1962). This was to be expected from the overall similar herbicide response of grafted and non grafte d watermelon in the field study. The differences in herbicide translocation and herbicide tolerance between cucumber and squash seen by Baker and Warren (1962) also corresponded with one another.

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54 Table 5 1. Sources of materials used in grafte d watermelon uptake and translocation study 1 Seed of TRI X Brand 313, Emphasis, and Strong Tosa, Syngenta International AG, P.O. Box, CH 4002 Basel, Switzerland 2 Plastic pots 700026C, T.O. Plastics, Inc., P.O. Box 37, Clearwater, MN 55320 3 Premium Play Sand, Quikrete, One Securities Centre, 3490 Piedmont Rd., Suite 1300, Atlanta, GA 30305 4 Kodak X OMAT XAR 5 film, Sigma Aldrich, 3050 Spruce St., St. Louis, MO 63103 5 Wiley Mill, Arthur H Thomas Company, Philadelphia, PA 6 R.J. Harvey Biological Oxidize r Model OX 500, R.J. Harv ey Instrument Co., 11 Jane St., Tappan, NY 10983 7 R.J. Harvey 14 Carbon Cocktail (proprietary blend of biscumene and PPO ( diphenyloxazole) in mixed xylenes), R.J. Harvey Instrument Co., 123 Patterson St., Hillsdale, NJ 07642 8 Pac kard Tricarb 1600CA Liquid Scintillation Analyzer, Packard Instrument Co., 800 Research Parkway, Meriden, CT 06450 9 SAS 9.1, SAS Institute Inc., 100 SAS Campus Drive, Cary, NC 27513

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55 Figure 5 1. Trial 1 autoradiographs of 14 C atrazine treated plants at 24 and 72 hours after treatment. 24 HOURS 72 HOURS BG HS SELF NON

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56 Figure 5 2. Trial 2 pressed plants (left) and autoradiographs (right) of 14 C atrazine treated plants at 24 and 72 hours after treatment. 72 HOURS 24 HOURS BG BG HS HS SE LF SELF NON NON

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57 Figure 5 3. Trial 1 autoradiogr aphs of 14 C glyphosate treated plants at 24 and 72 hours after treatment. 24 HOURS 72 HOURS BG HS SELF NON

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58 Figure 5 4. Trial 2 pressed plants (left) and autoradiographs (right) of 14 C glyphosate treated plants at 24 and 72 hours after treatment. 24 HOURS 72 HOURS BG BG HS HS SELF SELF NON NON

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59 Table 5 2 Uptake and tra nslocation of 14 C atrazine at 24 a nd 72 hours after treatment in t rial 1. a 24 hour 72 hour BG b HS SELF NON BG HS SELF NON --------------% of applied --------------------------% of applied -------------Total 14 C uptake 9.2 b 24.0 a 7.2 b 9.3 b 16.2 b 29.1 a 13.3 b 17.4 b --------% of absorbed activity --------------% of absorbed activity -------Root 24.8 a 17.8 b 16.2 b 8.6 c 16.5 a 15.9 ab 10.3 bc 5.2 c Shoot 75.2 c 82.2 b 83.8 b 91.4 a 83.5 c 84.1 bc 89.7 ab 94.8 a a F or each harvest, means within rows followed by the same letter are not significantly different b Abbreviations: BG, watermelon grafted onto bottle gourd; HS, watermelon grafted onto interspecific hybrid squash; SELF, watermelon grafted onto watermelon; NON, non grafted watermelon. Table 5 3 Uptake and translocation of 14 C atrazine at 24 a nd 72 hours after treatment in t rial 2 a 24 hour 72 hour BG b HS SELF NON BG HS SELF NON --------------% of applied ---------------------------% of applied -------------Total 14 C uptake 13.2 a 11.9 a 11.4 a 9.7 a 14.3 b 19.6 a 14.5 b 14.3 b --------% of absorbed activity ---------------% of absorbed activity -------Root 32.2 a 28.6 a 17.6 b 15.9 b 14.1 a 16.1 a 5.9 b 12.8 a Shoot 67.8 b 71.4 b 82.4 a 84.1 a 85.9 b 83.9 b 94.1 a 87.2 b a For each harvest, means within rows follo wed by the same letter are not significantly different b Abbreviations: BG, watermelon grafted onto bottle gourd; HS, watermelon grafted onto interspecific hybrid squash; SELF, watermelon grafted onto wa termelon; NON, non grafted watermelon.

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60 Table 5 4 Uptake and translocation of 14 C glyphosate at 24 a nd 72 hours after treatment in t rial 1. 24 hour 72 hour BG a ST SELF NON BG ST SELF NON --------------% of applied --------------------------% of applied -------------Total 14 C uptake 94.0 73.7 90.3 86.8 97.0 85.9 84.6 88.0 Leaf rinse 5.7 9.8 8.8 11.9 3.2 6.6 2.6 4.6 --------% of absorbed activity ---------------% of absorbed activity -------Root 1.2 2.6 2.0 1.4 2.8 4.2 2. 6 3.1 Shoot 3.6 6.5 2.4 7.4 6.7 16.0 9.8 15.7 Treated leaf 95.1 90.9 95.7 91.2 90.6 79.8 87.6 81.2 a Abbreviations: BG, watermelon grafted onto bottle gourd; HS, watermelon grafted onto interspecific hybrid squash; SELF, watermelon grafted onto watermelo n; NON, non grafted watermelon. Table 5 5 Uptake and translocation of 14 C glyphosate at 24 a nd 72 hours after treatment in t rial 2. 24 hour 72 hour BG a ST SELF NON BG ST SELF NON --------------% of applied ---------------------------% o f applied -------------Total 14 C uptake 65.6 57.3 67.3 61.7 74.3 70.8 67.7 67.8 Leaf rinse 2.3 7.5 5.4 6.3 1.8 2.4 2.3 2.7 --------% of absorbed activity ---------------% of absorbed activity -------Root 2.9 2.7 2.0 3.5 2.4 4.1 5.5 2.5 Shoot 1 1.8 10.0 8.0 15.0 13.5 17.2 16.7 17.5 Treated leaf 85.4 87.2 90.1 81.6 84.1 78.6 77.8 80.0 a Abbreviations: BG, watermelon grafted onto bottle gourd; HS, watermelon grafted onto interspecific hybrid squash; SELF, watermelon grafted onto watermelon; NON, n on grafted watermelon.

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61 Table 5 6 Trial 1 average dry weights of roots and shoots. a Dry w eight BG b HS SELF NON ----------------------------------------g ---------------------------------------Root 0.51 a 0.36 b 0.15 c 0.15 c Shoot 0.98 b 0. 97 b 0.60 c 1.15 a a For each harvest, means within rows followed by the same letter are not significantly different b Abbreviations: BG, watermelon grafted onto bottle gourd; HS, watermelon grafted onto interspecific hybrid squash; SELF, watermelon grafted onto watermelon; NON, non grafted watermelon. Table 5 7 Trail 2 average dry weights of roots and sho ots. a Dry w eight BG b HS SELF NON ----------------------------------------g ---------------------------------------Root 0.43 a 0.40 ab 0.21 c 0.33 b Shoot 0.93 b 0.89 b 0.92 b 1.24 a a For each harvest, means within rows followed by the same let ter are not significantly different b Abbreviations: BG, watermelon grafted onto bottle gourd; HS, watermelon grafted onto interspecific hybrid squash; SELF, watermelon grafted onto watermelon; NON, non grafted watermelon.

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62 CHAPTER 6 CONCLUSIONS Watermelon [ Citrullus la natus (Thunb.) Matsumura and Nakai] growers may adopt grafting as an alternative to methyl bromide fumi gation for soil borne pest control. Herbicide t olerance is one of various production considerations that needed to be studied in order to reduce the ris k of damaging a n expensive grafted watermelon planting Field studies examined terbacil, halosulfuron, clomazone, and S metolachlor use in non grafted watermelon and watermelon grafted onto bottle gourd [ Lagenaria siceraria (Mol.) Standl.] and interspecif ic hybrid squas h ( Cucurbita maxima x C. moschata ) Some herbicide appli cations were known to be safe on non grafted watermelon. However, the tolerance of watermelon grafted o nto a rootstock of another cucurbit species to the same application was unknown. Furthermore, other herbicide applications were previously known to damage non grafted watermelon although other cucurbits are tolerant The goal of this research was to determine if grafted watermelon has m ore or less tolerance of herbicides compared to non grafted watermelon. The low rate of terbacil labeled for use in watermelon production was also safe for use in watermelon grafted onto bottle gourd and interspecific hybrid squash. Although wat ermelon is naturally tolerant to terbacil, many other cuc urbits are considered quite sensitive (Anderson et al. 1995; Beste 1989; Genez and Monaco 1983) Although wate rmelon was grafted onto rootstock of other cucurbit species the watermelon scion exhibited no injury. This is likely due to the mode of action of terbacil. Since terbacil is a photosynthe tic inhibitor, potential injury may have been avoided since the other species were only used as a rootstock Halosulfuron PRE was safe on watermelon grafted to bottle gourd and interspecific hybrid squash just a s for non grafted waterme lon when evaluated in Florida and South Carolina. However, halosulfuron POST injured grafted watermelon just as Dittmar et al. (2008) reported in

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63 non grafted watermelon. Cucurbit tolerance to halosulfuron POST is variable as this application is labeled for use in many cucurbit crops (Olson et al. 2011). No additional tolerance of watermelon to halosulfuron POST was imparted by grafting onto bottle gourd or interspecific hybrid squash. Clomazone bleaching was evident on non grafte d and gr afted watermelon. Cohen et al. (2008) also reported bleaching when watermelon was grafted onto inter specific hybrid squash As their report found no bleaching on interspecific hybrid squash rootstock when tested alone, it is likely that even thou gh certain rootstocks may be more tolerant to cl omazone, grafted watermelon will still exhibit injury if clom azone translocates into the scion S metolachlor tole rance was variable across locations. When injury occurred, it was seen on grafted and non gra fted plants. In Florida, injury was greater in 2010 compared to 2009. The tolerance of S metolachlor in grafted and non grafted watermelon will likely depend on the environment in which it is applied. For example, cool and wet conditions can lead to gre ater metolachlor crop injury (Viger et al. 1991). Grafted and non grafted watermelon generally grew out of herbicide injury and produced total yie lds similar to un treated plants. Yield impact was usually more prominent when examining early yield. However early yield is very important due to the higher crop value early in the season. As in the field studies, grafted and no n grafted watermelon plants had overall similar results in the lab oratory Herbicide translocation was similar in grafted and non graf ted plants based on liquid scintillation spectrometry and autoradiography. Although non grafted and self grafted watermelon had greater translocation of absorbed atrazine compared to watermelon

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64 grafted onto bottle gourd and interspecific hybrid squash, th e difference was not likely great enough to significantly alter herbicide tolerance Atrazine uptake was greater when watermelon was grafted on to interspecific hybrid squash. In trial 1, twice the uptake was seen with this rootstock compared to others. Although rootstock did not have much of an impact on herbicide tolerance in the field studies described here such a difference in soil applied herbicide uptake could play a role in grafted watermelon tolerance of other herbicides. Grafted and non grafted watermelon performed simi larly in uptake and translocation of glyphosate. This may explain the similar halosulfuron POST injury wit h grafted and non grafted watermelon As most of the applied glyphosate remained in the treated leaf at 72 hours aft er tre atment, future research with a later harvest time would be important to further define translocation

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65 LITERATURE CITED Alan, ., N. zemir, and Y. Gnen. 2007. Effect of grafting on watermelon plant growth, yield and quality. J. Agron. 6 (2): 362 365. A nderson, M. P., C. Bensch, J. F. Stritzke, and J. L. Caddel. 1995. Uptake, translocation, and metabolism in alfalfa ( Medicago sativa ) selected for enhanced tolerance to terbacil. Weed Science 43:365 369. Anderson, W. P. 1996. Weed Science: Principles and Applications. 3 rd ed. St Paul, MN: West Publishing Company. 388 pgs. Andrews, P. K. and C. Serrano Marquez. 1993. Graft incompatibility. Pages 183 232 in Jules Janick, ed. Horticultural Reviews volume 15. New York, NY: John Wiley and Sons, Inc. Anonymou s. 2002. Command 3ME Microencapsulated Herbicide Product Label. Philadelphia, PA: FMC Corporation. Anonymous. 2009. Sinbar Agricultural Herbicide Product Label. Phoenix, AZ: Tessenderlo Kerley, Inc. Anonymous. 2007. Sandea Herbicide Product Label. Yum a, AZ: Gowan Company, L.L.C. Anonymous. 2011. Dual Magnum Herbicide Product Label. Greensboro, NC: Syngenta Crop Protection, L.L.C. Baker, R. S. and G. F. Warren. 1962. Selective Herbicidal Action of Amiben on Cucumber and Squash. Weeds 10:219 224. Best e, C. E. 1989. Terbacil selectivity for watermelon. British Crop Prot. Conf. 3:1045 1048. Chouka, A. S. and H. Jebari. 1999. Effect of grafting on watermelon vegetative and root development, production and fruit quality. Acta Hort. 492:85 93. Cohen, R., H Eizenberg, M. Edelstien, C. Horev, T. Lande, A. Porat, G. Achdari, and J. Hershenhorn. 2008. Evaluation of herbicides for selective weed control in grafte d watermelons. Phytoparasitica 36(1):66 73. Colla, G., Y. Rouphael, M. Cardarelli, O. Temperini, S Fanasca, F. Pierandrei, A. Salerno, and E. Rea. 2007. Salt tolerance and mineral relations for grafted and ungrafted watermelon plants grown in NFT. Acta Hort. 747:243 247. Corbin, F. T. and B. A. Swisher. 1986. Radioisotope Techniques. Pages 265 276 i n Research Methods in Weed Science. Champaign, IL: Southern Weed Science Society. Core, J. 2005. Grafting watermelon onto squash or gourd rootstock makes firmer, healthier fruit. Agricultural Research. Pages 8 9.

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66 Cushman, K. 2006. Grafting techniques for watermelon. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences Document HS1075. Davis, A. R., P. Perkins Veazie, R. Hassell, A. Levi, S. R. King, X. Zhang. 2008a. Grafting effects on vegetable quality. HortScience 43(6):1 670 1672. Davis, A. R., P. Perkins Galarza, J. V. Maroto, S. G. Lee, Y. C. Huh, Z. Sun, A. Miguel, S. R. King, R. Cohen, and J. M. Lee. 2008b. Cucurbit grafting. Critical Reviews in Plant Sciences 27(1):50 74. Dittmar, P. J., D. W. Monks, J. R. Schultheis, and K. M. Jennings. 2008. Effects of postemergence and postemergence directed halosulfuron on triploid watermelon ( Citrullus lanatus ). Weed Technol. 22:467 471. Eastin, E. F. 1986. Absorption, translocation, and degradation of herbicides by plants. Pages 277 289 in Research Methods in Weed Science. Champaign, IL: Southern Weed Science Society. Genez, A. L. and T. J. Monaco. 1983. Uptake and translocation of terbacil in strawberry ( Fragaria x ananassa ) and goldenrod ( Solid ago fistulosa ). Weed Science 31:56 62. Goreta, S., V. Bucevic Popovic, G. V. Selak, M. Pavela Vrancic, and S. Perica. 2008. Vegetative growth, superoxide dismutase activity and ion concentration of salt stressed watermelon as influenced by rootstock. J. of Agric. Sci. 146:695 704. Grey, T. L., D. C. Bridges, and D. S. NeSmith. 2000. Tolerance of cucurbits to the herbicides clomazone, ethalfluralin, and pendimethalin. II. Watermelon. HortScience 35(4):637 641. Harrison Jr., H. F., C. S. Kousik, and A. Lev i. 2010. Tolerance to the herbicide clomazone in watermelon plant introductions. HortScience 45:510. Hassell, R. H., F. Memmott, and D. G. Liere. 2008. Grafting Methods for Watermelon Production. HortScience 43(6):1677 1679. Hohlt, H. E., H. P. Wilson, a nd T. E. Hines. 1990. The use of low rates of clomazone on watermelon. HortScience 25(8) :857. Kemble, J. M. (ed.). 2010. Vegetable Crop Handbook for Southeastern US 2010. Lincolnshire, IL: Vance Publishing Corp. King, S. R., A. R. Davis, W. Liu, and A. L evi. 2008. Grafting for disease resistance. HortScience 43(6):1673 1676. Kubota, C., M. A. McClure, N. Kokalis Burelle, M. G. Bausher, and E. N. Rosskopf. 2008. Vegetable grafting: history, use, and current technology status in North America. HortScienc e 43(6):1664 1669.

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67 Lee, J. M. 1994. Cultivation of grafted vegetables I. Current status, grafting methods, and benefits. HortScience 29(4):235 239. Lee, J. M. and M. Oda. 2003. Grafting of herbaceous vegetable and ornamental crops. Hortic. Rev. 28:61 124 MacRae, A. W., A. S. Culpepper, R. B. Batts, and K. L. Lewis. 2008. Seeded watermelon and weed response to halosulfuron applied preemergence and postemergence. Weed Technol. 22:86 90. Miguel, A., J. V. Maroto, A. San Bautista, C. Baixauli, V. Cebolla, L. Guardiola. 2004. The grafting of triploid watermelon is an advantageous alternative to soil fumigation by methyl bromide for control of Fusarium wilt. Scientia Hort. 103:9 17. Noling, J. W., D. A. Botts, and A. W. MacRae. 2009. Alternatives to methyl bromide soil fumigation for Florida vegetable production. Pages 43 50 in S. M. Olson and E. Simonne, eds. Vegetable Production Handbook for Florida. Lincolnshire, IL: Vance Publishing. Olson, S. M., E. H. Simonne, W. M. Stall P. D. Roberts, S. E. Webb, T. G. Taylor, S. A. Smith, and J. H. Freeman. 2007. Cucurbit production in Florida. Pages 201 250 in S. M. Olson and E. Simonne, eds. Vegetable Production Handbook for Florida. Lincolnshire, IL: Vance Publishing. Olson, S. M ., E. H. Simonne, W. M. Stall, P. D. Roberts, S. E. Webb, and S. A. Smith. 2011. Cucurbit production in Florida. Pages 85 107 in S. M. Olson and B. Santos, eds. Vegetable Production Handbook for Florida. Lincolnshire, IL: Vance Publishing. Paplomatas, E. J., K. Elena, A. Tsagkarakou, and A. Perdikaris. 2002. Control of Verticillium wilt of tomato and cucurbits through grafting of commercial varieties on resistant rootstocks. Acta Hort. 579:445 449. Rothenberger, R. R. and C. J. Starbuck. 2008. Grafting. University of Missouri Extension Document G6971. SAS Institute Inc. 2003. SAS 9.1. Cary, NC. Senseman, S. A., ed 2007. Herbicide Handbook. 9 th ed. Lawrence, KS: Weed Science Society of America. 458 pgs. Taylor, M., B. Bruton, W. Fish, and W. Roberts. 2 006. Cost benefit analysis of using grafted watermelons for disease control and the fresh cut market. In: Cucurbitaceae 2006. Pages 277 285. Viger, P. R., C. V. Eberlein, and E. P. Fuerst. 1991. Influence of available soil water content, temperature, an d CGA 154281 on metolachlor injury to corn. Weed Science 39:227 231.

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68 Wehtje, G., M. E. Miller T. L. Grey, and W. R. Brawner Jr 2007. Comparisons Between X Ray Film and Phosphorescence Imaging Based Autoradiography for the Visualization of Herbicide Tr anslocation. Weed Technol. 21:1109 1114. Yamaguchi, S. and A. S. Crafts. 1958. Autoradiographic method for studying absorption and translocation of herbicides using C 14 labeled compounds. Hilgardia 28:161 191. watermelon fruit yield and quality. Phytoparasitica 31(2):163 169. watermelon seedlings grafted on rootstocks with different emergence performance at various temperatures. Turk. J. Agric. For. 28:231 237.

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69 BIOGRAPHICAL SKETCH Joshua Adkins grew up in Homeland, Florida. He graduated from Bartow Senior High School in 2002. That fall, he began coursework at Florida Southern College (Lakeland, Florida). In the spring of 2006, he received a Bachelor of Science degree in horticul tural science with a minor in business administration. The next August, he began studies at the University of Florida on a Master of Science degree in horticultural science. After completing the Mas ter of Science degree, he remained at the University of Florida to pursue a Doctor of Philosoph y degr ee