University of Florida Thesis Or Dissertation Formatting

DEVELOPMENT OF AN INTEGRATED APPROACH FOR MANAGING MELON THRIPS, THRIPS PALMI KARNY (THYSANOPTERA: THRIPIDAE) IN VEGETABLE CROPS

MOHAMMAD ABDUR RAZZAK

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

2018 1

To my parents

ACKNOWLEDGMENTS

First of all, I would like to thank almighty Allah for helping me to complete the long journey at the University of Florida to pursue PhD degree. I would like to express my deepest gratitude to Dr. Dakshina Seal for serving as my major advisor and providing me with an opportunity to pursue my goals in entomology at the University of Florida. His scientific guidance, knowledge, comprehension, and friendship have been invaluable. I am also very grateful to other members of my supervisory committee including Dr. Philip A. Stansly, Dr.

Oscar E. Liburd and Dr. Bruce Schaffer for their guidance and support to accomplish the research work and writing the dissertation. I acknowledge Dr. James Colee (University of

Florida-Statistics Department) for his generous support and sincere effort in statistical analyses.

I am thankful to my lab members Cathie Sabines, Dr. Cliff G. Marin, Shawbeta Seal and

Rafia Khan for their help and mental support to accomplish this researsch. I am greatly indebted to my wife (Nurun Nahar) for her support in processing the leaf samples to separate thirps and mites. I don’t know where I would be without her support. She was also enormously patient in staying home lonely while I was busy with my assignment in the laboratory and field. I also sincerely appreciate my three-year old son, Abdur Rafi’s patience while his mother was washing leaf samples. My thanks go to Jose Castillo and his staff for helping in research field preparation and fertilizer application. Special recognition goes to IMAFLEX Inc. USA for providing me with plastic mulch to conduct this study. I also acknowledge Koppert Biological systems and Costa

Farms (Homestead, FL) for helping me with predatory mites. Thanks to Rita Duncan and Ana

Vargas for helping me in leaf trichome density estimation and measuring leaf area.

Finally, last but not the least, my special gratitude goes to my parents who brought me up and supported to continue my study in Bangladesh with their limited resource but with boundless love and affection.

TABLE OF CONTENTS

page

ACKNOWLEDGMENTS ...... 4

LIST OF TABLES ...... 9

ABSTRACT ...... 13

CHAPTER

1 LITERATURE REVIEW ...... 15

Overview of Florida Vegetable Production ...... 15 Melon Thrips Role as a Pest ...... 15 Host Range and Preference ...... 18 Geographical Distribution ...... 20 Morphological Characters ...... 20 Life cycle, Biology and Ecology ...... 21 Seasonal Prevalence ...... 23 Population Density ...... 23 Within-Plant Distribution ...... 24 Insecticide Based Management of Melon Thrips ...... 25 Integrated Pest Management (IPM) ...... 27 Plastic Mulch and Vegetable Production ...... 27 Plastic Mulch and Insect Pest Management Including Melon Thrips ...... 28 Late Season Effect of Mulch on Insect Populations ...... 32 Effect of Mulch on the Growth and Development of Vegetable Crops ...... 33 Effect of Mulch on the Yield of Vegetable Crops ...... 34 Accumulation of Mineral Nutrients and Thrips Abundance ...... 36 Morphological Characteristics of Plants and Thrips Population ...... 37 Role of Amblyseius swirskii in Biological Control ...... 37 Effect of Reflective Plastic Mulch on Predatory or Parasitic Insects ...... 38 Research Objectives ...... 39

2 EFFECTIVENESS OF DIFFERENT PLASTIC MULCHES IN MANAGING MELON THRIPS ON SIX FIELD-GROWN VEGTABLE CROPS IN SOUTHERN FLORIDA ...... 40

Introduction ...... 40 Materials and Methods ...... 44 Study Area, Crop Varieties, Plastic Mulches, Field Preparation, Plot Design, and Mulch Placement ...... 44 Crop Establishment ...... 45 Crop Management ...... 46 Leaf Samples ...... 46

Leaf Mineral Nutrients ...... 47 Trichome Density Estimation ...... 48 Weather Data ...... 49 Data Analyses ...... 49 Results...... 50 Effects of Mulches and Interactions Between Date and Mulch on the Abundance of Melon Thrips ...... 50 Adult density ...... 50 Larval density ...... 50 Total numbers of melon thrips ...... 51 Effects of Crops and Interactions Between Date and Crop on the Abundance of Melon Thrips ...... 52 Adult density ...... 52 Larval density ...... 53 Total numbers of melon thrips ...... 54 Date Effect on the Abundance of Melon Thrips ...... 54 Adult density ...... 54 Larval density ...... 55 Total numbers of melon thrips ...... 55 Weather Condition ...... 55 Trichome Density ...... 55 Leaf Mineral Nutrients ...... 56 Discussion ...... 56 Mulch Effects ...... 56 Crop Effects ...... 60 Date Effects ...... 63 Implications and Future Studies ...... 66

3 EFFECTS OF PLASTIC MULCHES ON WITHIN PLANT DISTRIBUTIONS OF MELON THRIPS, THRIPS PALMI (THYSANOPTERA: THRIPIDAE) IN VEGETABLE CROPS ...... 78

Introduction ...... 78 Materials and Methods ...... 81 Leaf Sampling and Processing for Thrips and Leaf Area Measurement ...... 81 Leaf Mineral Nutrient Analysis ...... 82 Data Analyses ...... 82 Results...... 83 Leaf Area ...... 83 Within-Plant Distributions ...... 83 Snap Beans ...... 84 Stratum effects ...... 84 Stratum and mulch interactions ...... 84 Mulch effects ...... 84 Cucumber ...... 85 Stratum effects ...... 85 Stratum and mulch interactions ...... 85

Mulch effects ...... 86 Eggplant ...... 86 Stratum effects ...... 86 Stratum and mulch interactions ...... 87 Mulch effects ...... 87 Jalapeno Pepper ...... 88 Stratum effects ...... 88 Stratum and mulch interaction ...... 88 Mulch effects ...... 89 Squash ...... 89 Stratum effects ...... 89 Stratum and mulch interactions ...... 90 Mulch effects ...... 90 Tomato ...... 91 Stratum effects ...... 91 Mulch and stratum interactions ...... 91 Mulch effects ...... 91 Leaf Mineral Nutrients ...... 92 Discussion ...... 92 Mulch Effects ...... 92 Stratum effects ...... 93 Mulch and Stratum Interactions ...... 96 Implications ...... 99

4 GROWTH AND YIELD RESPONSE OF FIELD GROWN VEGETABLE CROPS TO DIFFERENT PLASTIC MULCH TREATMENTS ...... 115

Introduction ...... 115 Materials and Methods ...... 118 Plant Growth and Biomass ...... 118 Yield ...... 119 Data Analyses ...... 120 Results...... 121 Height, Width and Dry Biomass ...... 121 Snap beans ...... 121 Jalapeno pepper ...... 121 Eggplant ...... 122 Squash ...... 122 Tomato ...... 123 Cucumber ...... 123 Yield ...... 124 Snap Beans ...... 124 Tomato ...... 124 Eggplant ...... 125 Cucumber ...... 125 Squash ...... 125 Jalapeno pepper ...... 126

Discussion ...... 126

5 COMBINED EFFECTS OF PLASTIC MULCH AND AMBLYSEIUS SWIRSKII ATHIUS- HENRIOT IN MANAGING MELON THRIPS, THRIPS PALMI KARNY (THYSANOPTERA: THRIPIDAE) ON FIELD GROWN VEGETABLE CROPS ...... 135

Introduction ...... 135 Materials and Methods ...... 138 Field Design, Mulch and Crop Types for 2015 Experiment ...... 139 Field Design, Mulch and Crop Types for 2016 Experiment ...... 139 Crop Establishment ...... 140 Source and Maintenance of A. swirskii ...... 140 Prerelease Sampling and A. swirskii Application ...... 140 Evaluation Method ...... 141 Within-Plant Distributions of A. swirskii ...... 142 Statistical Analyses ...... 142 Results...... 143 Effects of A. swirskii and Mulch Treatments on Melon Thrips ...... 143 Crop and Mulch Effects on A. swirskii ...... 145 Crop and Mulch Effects on the Within-Plant Distributions of A. swirskii ...... 145 Discussion ...... 146

6 SUMMARY AND CONCLUSIONS ...... 160

LIST OF REFERENCES ...... 164

BIOGRAPHICAL SKETCH ...... 191

LIST OF TABLES

Table page

2-1 Crop leaf areas on 10 sampling dates (5 per year) (Mean ± SEM cm2)...... 67

2-2 ANOVA of the effects of date, mulch, and crop on the abundance of adult melon thrips (T. palmi) per 25 cm2 leaf area from six vegetable crops grown on five different plastic mulches and a non-mulch control...... 67

2-3 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area in different mulch treatments; sampling dates and crops pooled*...... 68

2-4 Mean ± SE number of melon thrips adults (T. palmi) from treatments with different plastic mulches and a no-mulch control based on density per 25 cm2 leaf area of six vegetable crops...... 68

2-5 ANOVA of the effects of date, mulch, and crop on the abundance of melon thrips (T. palmi) larva per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control...... 69

2-6 Mean ± SE number of melon thrips (T. palmi) larvae in five different plastic mulches and a non-mulch control based on density per 25 cm2 leaf area of six vegetable crops...... 70

2-7 ANOVA of the effects of date, mulch, and crop on the abundance of total (adults plus larvae) number of melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control...... 71

2-8 Mean ± SE number of melon thrips (T. palmi) adults plus larvae in five different plastic mulches and a non-mulch control based on density per 25 cm2 leaf area of six vegetable crops...... 72

2-9 Mean ± SE number of different stages of melon thrips (T. palmi) per 25 cm2 leaf area of six different vegetable crops grown on five different plastic mulches and a non- mulch control (across the sampling period)...... 73

2-10 Mean ± SE number of adult melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control...... 73

2-11 Mean ± SE number of melon thrips (T. palmi) larvae per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control ...... 74

2-12 Mean ± SE number of total counts (adults and larvae) of melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control ...... 75

2-13 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control; on each sampling date...... 75

2-14 Weekly climate in the study area of the year 2015 and 2016...... 76

2-15 Mean ± SEM number of trichome per 1000μm2 leaf area of different host crops...... 76

2-16 Percent concentration (ppm) of Nitrogen (N), Phosphorus (P), Potassium (K), Boron (B), Zinc (Zn), Copper (Cu), Iron (Fe) and Manganese (Mn) in the middle stratum leaves of six vegetable crops grown on different mulches...... 77

3-1 Leaf areas of six vegetable crops at three strata on different sampling dates...... 101

3-2 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area at three different strata of snap beans, cucumber and eggplant; mulch treatments were pooled...... 102

3-3 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area at three different strata of Jalapeno pepper, squash and tomato; mulch treatments were pooled...... 103

3-4 Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of snap beans on 35 DAP and 46 DAP...... 104

3-5 Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of cucumber on 35 DAP and 50 DAP...... 105

3-6 Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of eggplant on 45 DAP and 60 DAP...... 106

3-7 Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of Jalapeno pepper on 42 DAP and 54 DAP...... 107

3-8 Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of squash on 30 DAP and 50 DAP...... 108

3-9 Mean ± SE number of melon thrips (T. palmi) per one leaf at different stratum of tomato on 40 DAP and 55 DAP...... 109

3-10 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of snap beans and cucumber grown on different plastic mulches and a no-mulch; strata were pooled...... 110

3-11 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of eggplant and jalapeno pepper grown on different plastic mulches and a no-mulch; strata were pooled...... 111

3-12 Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of squash and tomato grown on different plastic mulches and a no-mulch; strata were pooled...... 112

3-13 Percent concentration (ppm) of Nitrogen (N), Phosphorus (P) and Potassium (K) in different stratum leaves of six vegetable crops grown on different mulches...... 113

3-14 Percent concentration (ppm) of Boron (B), Zinc (Zn), Copper (Cu), Iron (Fe) and Manganese (Mn) in different stratum leaves of six vegetable crops grown on different mulches...... 114

4-1 Mean ± SE height and width (in cm) of six vegetable crops grown on different plastic mulches and a no-mulch in 2015 ...... 130

4-2 Mean ± SE height and width (in cm) of six vegetable crops grown on different plastic mulches and a no-mulch in 2016...... 131

4-3 Mean ± SE dry biomass (in gm) of six vegetable crops grown on different five plastic mulches and a no-mulch in fall 2016...... 132

4-4 Mean ± SE yields of six vegetable crops grown on different plastic mulches and a no- mulch in the Fall 2015 and 2016...... 133

4-5 Mean ± SE yields of six vegetable crops grown on different plastic mulches and a no- mulch in the Fall 2015 and 2016...... 134

5-1 ANOVA assessing the effects of A. swirskii and different mulch treatments on the abundance of melon thrips in different vegetable crops, 2015...... 152

5-2 ANOVA assessing the effects of A. swirskii and three different mulch treatments on the abundance of melon thrips in cucumber and eggplant, 2016...... 152

5-3 Mean ± SE number of melon thrips (T. palmi) with the effect of A. swirskii, regardless of crop and mulch, 2015...... 153

5-4 Mean ± SE number of melon thrips (T. palmi) with the effect of A. swirskii, regardless of crop and mulch, 2016...... 153

5-5 Mean ± SE number of melon thrips (T. palmi) in different crops with the effect of A. swirskii, regardless of mulch, 2015...... 153

5-6 Mean ± SE number of melon thrips (T. palmi) in cucumber and eggplant with the effect of A. swirskii, regardless of mulch, 2016...... 154

5-7 Mean ± SE number of melon thrips (T. palmi) in different mulches with the effect of A. swirskii, regardless of crop, 2015...... 154

5-8 Mean ± SE number of melon thrips (T. palmi) in different mulches with the effect of A. swirskii, regardless of crop, 2016...... 155

5-9 ANOVA assessing the effects of crops and mulch on the abundance of A. swirskii, regardless of mulch...... 155

5-10 Mean ± SE number of A. swirskii in different crops, regardless of mulch treatment...... 156

5-11 Mean ± SE number of A. swirskii in different mulch, regardless of crop treatment...... 157

5-12 ANOVA assessing the effects of crop and mulch on the distribution of A. swirskii in different strata of host plants...... 157

5-13 Mean ± SE number of A. swirskii in different strata of different mulches, regardless of crops...... 158

5-14 Mean ± SE number of A. swirskii on different strata of cucumber and eggplant, regardless of mulch treatments, 2016...... 159

5-15 Mean ± SE number of A. swirskii on different strata, regardless of crops and mulches, 2016...... 159

Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy

DEVELOPMENT OF AN INTEGRATED APPROACH FOR MANAGING MELON THRIPS, THRIPS PALMI KARNY (THYSANOPTERA: THRIPIDAE) IN VEGETABLE CROPS

Mohammad A. Razzak

August 2018

Chair: Dakshina R. Seal Major: Entomology and Nematology

Melon thrips, Thrips palmi Karny, is a serious pest of vegetable crops and ornamental plants. Using different chemical insecticides is a principal tool to manage this pest. Foliar applications of the same chemicals repetitively resulted in reduced susceptibility and limited control. As a component of an integrated pest management program, effectiveness of different plastic mulches (white on black, black on white, black on black, two metalized UV-reflective, and a non-mulch control) in managing melon thrips on six field grown vegetable crops (eggplant, cucumber, squash, snap beans, Jalapeno pepper and tomato) was studied during the Fall of 2015 and 2016. Metalized reflective mulch significantly reduced the number of melon thrips in all vegetable crops compared with the other mulch and control treatments. The highest numbers of melon thrips were observed in the white on black mulch and the control treatment.

Investigation was also performed to determine the within-plant distribution of melon thrips in three strata of each above-mentioned vegetable crops grown on the above-mentioned mulch treatments. There was a difference in the stratum preference by melon thrips adults and larvae. Overall, larvae were more abundant in the middle and bottom strata then in the top stratum. The number of adult was significantly greater in the middle and top strata than in the

bottom stratum. UV-reflective mulch reduced the number of melon thrips from all strata until plant canopy shaded the mulched area entirely.

Growth and yield response of six vegetable crops to different mulch treatments were also evaluated. Except for tomato, all vegetable crops on plastic mulch had higher vegetative growth and yields compared with no mulch treatment. Among the mulches, higher plant growth attributes and yields were observed in the reflective mulches.

Combined efficacy of Amblyseius swirskii Athias-Henriot and different plastic mulch treatments for managing melon thrips in field grown vegetable crops were assessed. Preventive release of Amblyseius swirskii effectively controlled melon thrips when thrips population abundance was low. The numbers of A. swirskii were similar in different mulch treatments.

These results suggest that reflective plastic mulch could be incorporated with an integrated management strategy for melon thrips.

CHAPTER 1 LITERATURE REVIEW

Overview of Florida Vegetable Production

Florida is a leading agricultural state for growing vegetable crops in the United States. In

2016, production of vegetable crops in Florida, such as tomato, squash, cucumber, bean, eggplant, and pepper, involved 107,000 acres of land and generated approximately $13,00 million thereby ranking it second in production among all the states. Florida is the main vegetable supplying state during late fall, winter, and early spring (United States Department of

Agriculture National Agricultural Statistics Service USDA/NASS 2016, Freeman et al. 2017).

However, bringing these crops from the field to the consumer is not easy because Florida vegetable growers have to combat many destructive native and invasive thrips species in addition to harmful insect pests, such as leaf miners, silver leaf whiteflies, beet and fall armyworms, melonworm, diamondback moths, cornsilk flies, and pepper weevils and many others economically important pests.

Melon Thrips Role as a Pest

Thrips (Order: Thysanoptera) as a whole is a large group totaling 6,151 extant species in

783 genera (ThripsWiki 2017). They are generally small with adult lengths measuring 1-4 mm.

Less than 100 species are economically important pests of various crops (Mound 1997). Thrips are polyphagous and feed on nearly 200 taxa of vegetable, fruit, and ornamental plants and are considered economically important global pest. They have a high fecundity and a short generation time. They are very active, thigmotactic and difficult to see. Their piercing, sucking mouth parts allow them to cause extensive feeding damage by emptying epidermal and mesophyll cells of their host plants, which reduces the photosynthetic potential, retards plant growth, deforms fruit, and reduces yields (Hunter and Ullman1989, 1992; Tipping 2008). In

addition, various thrips species cause serious crop loss by transmitting viral diseases. The crop loss due to tospoviruses and other viruses is estimated at over $1.4 billion during a 10-year period in the United States and have exceeded tens of millions of dollars around the world

(Rotenberg et al. 2015).

Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), is an invasive pest species to the United States of America which is native to Sumatra, Indonesia (Karny 1925, Johnson

1986). In the United States, T. palmi was first detected in Hawaii in 1982, then in Puerto Rico in

1986 and Florida in 1990 (Nakahara 1984, Johnson 1986, Sakimura et al. 1986, Seal and

Baranowski 1992). Since the invasion in Florida, T. palmi has been recognized as a devastating pest causing severe damage to snap beans, peppers, eggplants, cucumbers, watermelons, squash, potatoes, okra, and ornamental plants in the field and greenhouse (Faust et al. 1992, Hollinger

1992, Seal and Baranowski 1992, Seal 1994, Seal and Sabines 2012). Growers rated this pest as the highest concern for vegetable production in South Florida (Seal and Sabines 2012).

Infestation of peppers by T. palmi along with Frankliniella occidentalis (Pergande) in Palm

Beach County was responsible for over $3.9 million in economic damage (Nuessly and Nagata

1995). A serious outbreak of T. palmi was also occurred in Hawaii on cucurbits, eggplant, pepper, and amaranth spinach (Nakahara 1984).

Thrips palmi adults and larvae feed on the leaves along the midribs and veins, stems, flowers, and fruit of agronomic, vegetable crops and ornamental plants. It’s feeding on the cell contents often results in bronzing of leaves, stunting of whole plant and scarring and distortion of the fruit, which lowers the marketable yield (Kawai 1986; Wang and Chu 1986, 1990; Matsuzaki et al. 1986; Tsai et al. 1995; Nagata et al. 2002; MacLeod et al. 2004; Cannon et al. 2007b; Seal et al. 2013). In some instances, feeding damage can lead to 70-90% economic losses (Bournier

1983, Seal et al. 1993, Cardona et al. 2002). In some instances, without proper control measure complete defoliation of its host crops can occur from feeding damage within a week of the onset of infestation (Childers 1997, Seal 1997). Kawai (1986) and Suzuki and Miyara (1983) found positive relationship between the mean densities of T. palmi and fruit scaring on cucumbers.

Presence of one or less than one T. palmi per leaf of cucumber caused reduced number of tendrils, fewer leaves and increased plant mortality (Suzuki and Miyara 1983). In the tropics, estimated crop losses due to T. palmi infestation range from 15% for potatoes (Vercambre 1991) to 90% for cucumbers (Cooper 1990). Hall et al. (1993) stated that, 50-90% losses in vegetable crops occurred due to the infestation of melon thrips in Puerto Rico, Guadeloupe, Trinidad, and

Tobago. Greenhouses and field-grown cucumber, eggplant, and sweet pepper were severely injured by melon thrips in Japan (Kawai 1986, Matsuzaki et al. 1986).

Johnson (1986), reported heavy infestation and damage to watermelon foliage as bronzing and destruction of the vine tips. Pantoja et al. (1988) noticed severe damage to cucurbits and solanaceous commercial plantings in 1986 in Puerto Rico where pepper and aubergine plants became stunted with bronzed leaves and premature drop of developing fruit.

The growth of the cucumber plants was retarded, and heavy feeding damage resulted in reduced leaf dry weight (Welter et al. 1990). In South Florida, 75-95% defoliation with 100% loss recorded in snap beans (Seal 1997).

In addition to damage from the feeding by adults and larvae and from adult oviposition,

T. palmi is a known vector of at least six tospoviruses (Honda et al. 1989, Nagata et al. 2002,

Frei et al. 2005, Pappu et al. 2009, Reitz et al. 2011). These include watermelon silver mottle virus (Iwaki et al. 1984, Ullman et al. 1997), groundnut bud necrosis virus (Ullman et al. 1997,

Meena et al. 2005), melon spotted wilt virus, melon yellow spot virus (Kato et al. 2000), calla

lily chlorotic spot virus (CCSV) (Chen et al. 2005), watermelon bud necrosis virus (WBNV), and capsicum chlorosis virus (CCV) (Pappu et al. 2009, Reitz et al. 2011). Thrips palmi also has been reported to transmit an isolate of the tomato spotted wilt tospovirus (TSWV) that infects watermelon in Taiwan (Yeh et al. 1992) and in Japan (Iwaki et al. 1984, Honda et al. 1989). This and other thrips species may also transfer the spores of molds, mildews, and rusts from diseased to healthy plants (Gahukar 2004). Importantly, the presence of T. palmi also creates market access problems when other states and overseas countries impose restrictions on the movement of host plant materials from infested areas. This may ultimately result in economic losses and increased unemployment.

Host Range and Preference

Information on biology, ecology, and behavior of an insect pest is essential in developing an effective and sound management program. Moreover, specific and proper characterization of the reproductive hosts of an opportunist phytophagous species depend on reproductive success on various available hosts temporarily as well as spatially (Mound and Teulon 1995, de Kogel et al. 1997b). Thrips palmi is polyphagous and feeds on more than 50 plant species in over 20 families (Wang and Chu 1986, Walker 1992, Kirk 1997a). Miyazaki and Kudo (1988) reported that melon thrips attacks 117 species of plants in 34 families with the largest yield losses occurring on crops in the Cucurbitaceae and Solanaceae. In a 2005 report, Smith et al. listed 36 plants families as hosts of T. palmi with plants in family Solanaceae the most preferred. Thrips palmi attacks legumes and fruiting, and leafy vegetables in many tropical and subtropical countries (Bhatti 1980, Negai et al. 1981, Johnson 1986). Worldwide serious infestation by

Thrips palmi has been detected on plants from the Solanaceae (eggplants- Solanum melongena

L., pepper- Capsicum spp., potato- Solanum tuberosum L. and others), Cucurbitaceae

(cucumber- Cucumis sativus L., watermelon- Citrullus lanatus Thunb, cantaloupe- Cucumis

melo L., and pumpkin, zucchini, squash, edible gourds- Cucurbita spp., and others), and

Fabaceae (green bean, snap bean, kidney bean- Phaseolus vulgaris L., broad bean- Vicia faba L, cowpeas- Vigna unguiculata L., soybean- Glycine max L., and white clover- Trifolium repens L. and others) (Nakahara 1984, Talekar 1991, Cermeli and Montagne 1993). Thrips palmi feeds and breeds on all above-ground parts of its host plants (flowers, stems, leaves, and fruits) in field, greenhouse, and shade house conditions (Seal 1997). Among vegetable crops, based on larval and pupal developmental time cucumber was more suitable than eggplant, bell pepper and watermelon. However, bell pepper was the least suitable host than cucumber, eggplant, and watermelon (Tsai et al. 1995). Tomato (Family: Solanaceae) is reported as a feeding and reproductive host of T. palmi in the Caribbean (Capinera 2000) and in Miami-Dade County, FL

(D. R. Seal unpublished). Kawai (1990a) reported that melon thrips does not complete its life cycle on tomato and strawberry plants because larvae unable to pupate if feed on tomato and strawberry leaves. According to Hirano et al. (1994) α-tomatine in tomato leaves attributed to act as antifeedant for melon thrips. However, additional hosts include onion, cotton, avocado, citrus, peaches, plums, muskmelons, cantaloupe, hairy gourds, Chinese wax gourd, carnations and chrysanthemums (Ruhendi and Listinger 1979, Gutierez 1981, Wangboonkong 1981, Yoshihara

1982, Bournier 1983, Riddle-Swan and Kawai 1988, Childers and Beshear 1992, Monteiro et al.

1995). Tobacco, ground cherry, bittermelon, hyotan, togan, Chinese spinach and amaranth spinach, morning glory, sweet potato, orchids, sesame, mango, peach and various weeds also act as susceptible hosts for melon thrips (Karny 1925, Wang and Chu 1986, Seal 1997, Smith et al.

2005). Information regarding host preference or suitability of melon thrips in field condition over multi cropping system is largely unknown although such type of information is very important for crop selection in vegetable growing season and insect crop interaction.

Geographical Distribution

Thrips palmi is native to Southeast Asia (Karny 1925), afterward, human assisted dispersion occurred throughout the world (Lewis 1997, Mound 1997). It has spread to most of the Asian countries, many islands in the Pacific Ocean, and to northern Africa, Australia, Central and South America, and the Caribbean (Capinera 2000), although apparently absent from Europe

(NPPO Netherlands 2013).

Morphological Characters

Adults are 0.8-1.3 mm long with females slightly larger than males. Thrips palmi are clear to pale yellow except for the antennal segments, and they have many dark setae on the body though not on the head. A black line runs along the back of the body at the juncture of the wings, which are slender, fringed, and pale colored. The fringe or hairs on the anterior edge of each wing are considerably shorter than those on the posterior edge. There are seven antennal segments, which are similar to those on onion thrips, Thrips tabaci (Lindeman). However, on the head of T. palmi the three ocelli form a triangular shape, and a pair of setae helps to distinguish it from T. tabaci. Thrips palmi antennal segments I and II are pale colored, III is yellow with a shaded apex, IV to VII are brown, and the bases of segments IV-V are usually yellow. The post ocular setae II and IV are much smaller than the remaining setae. Ocellar setae III appears either just outside the ocellar triangle or touching the tangent lines connecting the anterior ocellus with each of the posterior ocelli. The metascutum has sculptures as parallel lines those converged posteriorly, a median pair of setae behind its anterior margin, and paired campaniform sensilla.

The first forewing vein has three (occasionally two) distal setae. There are two pairs of posteroangular setae on the pronotum of which outer pair is shorter than inner pair. Abdominal tergite II has four lateral marginal setae, Abdominal tergites III to IV have S2 setae which are dark and subequal to the S3 setae. The posteromarginal comb in the eighth abdominal segment is

complete. The ninth abdominal tergite usually has two pairs of pores (campaniform sensillae).

Both the sternites and pleurotergites in the abdominal region are devoid of discal setae. Also, abdominal sternites III-VII in males have a narrow transverse glandular area (Capinera 2000,

ISPM 2009, CABI).

Life cycle, Biology and Ecology

The life stages of melon thrips include the egg, two actively feeding larval instars, and two relatively inactive pupal instars (prepupa and pupa), and the adult (Lewis 1973). For virgin females preoviposition period is 1-3 days and 1-5 days for mated ones. Females lay up to 200 bean-shaped, colorless to pale white eggs in the tissues of leaves, flowers, and fruit of host plants by creating an incision with their saw-like ovipositor (Lewis 1973, Seal 1997, Capinera 2000,

Zang and Brown 2008). Virgin females lay 1.0-7.9 eggs per day, with 3-164 eggs lay in their life span. Mated females lay 0.8-7.3 eggs per day and lay 3-204 eggs during their life span (Wang et al. 1989, Wang and Chu 1990). The first-instar, a white, transparent larva, emerges from the egg within 4.3 days of oviposition at 32 oC, but the durations can be increased to 7.5 days and 16 days at 26 oC and 15 oC, respectively (Capinera 2000). At the end of the second instar, the larvae typically become yellowish and develop into a partially-feeding prepupal stage with a tiny outgrowth of wing pads. The prepupa descends to the soil surface or leaf litter for pupation

(Tsuchida 1997). Unlike prepupa, the pupal stage is completely non-feeding (Lewis 1973). At

15, 26, and 32 oC, the combined prepupal and pupal developmental time is 12, 4, and 3 days, respectively and finally turned in to an adult (Capinera 2000). The life span of T. palmi adult is

10 - 30 days for females and 7 - 20 days for males (Capinera 2000), average adult life span 17 day (range, 6-35 days) (Bueno and Cardona 2001). However, according to Tsai et al. (1995) adult female has longer longevity (13-24 days) than males (11.1-13.7 days) although longevity can be influenced by temperature (Yadav and Chang 2014).

Host plants as well as climatic factors have an important role on reproduction, development and longevity of an organisms. Kawai (1986) found the highest survival rate of preadult stage and maximum intrinsic rate of increase on cucumber, kidney bean (Phaseolus vulgaris), aubergine and balsam pears (Momordica charantia), followed by melon, pumpkin

(Cucurbita maxima) and pepper (Capsicum annuum). However, the generation times were not significantly varied between crops, being in the range of 21.2-25.9 days. On cucumbers, T. palmi reaches a maximum net reproductive rate at 25 oC, and the lowest optimum temperature of

o development for the pre-adult stage is 11.6 C (Kawai 1990a). The maximum rm for T. palmi occurred on cucumber and there was a fairly high rate on melons, eggplant, and pumpkins, the population growth on sweet pepper was not high (Kawai 1990a). Huang and Lin (2012) reported that on eggplant leaves performed highest fecundity (mx), the fecundity (fx) and the age specific

o maternity (lxmx), and the net reproductive rate (Ro) at 25 C. However, Tsai et al. (1995) found

o that at 26 C, compared to bell pepper net reproductive rate (Ro) was significantly highest on eggplant, cucumber and watermelon due to greatest survival and highest egg production although development times were similar on all four crops. Moreover, the highest intrinsic rate of natural

o increase (rm) occurred at 32 C on eggplant, cucumber and watermelon because of shorter development time whereas only 48% survived on bell pepper.

Threshold temperature for development of T. palmi and the thermal constant for preadult stages were estimated to be 11.6 oC and 189.1degree days, respectively (Kawai 1986a, 1990a). In

70-80% RH complete life cycle can be completed in about 20 days at 20-22 oC and 9.2 days at

32.5 oC and on cucumber and eggplant (Park et al. 2010, Yadav and Chang 2014). 25-30 oC was found to be optimum temperature for population growth and can complete 25- 26 generations each year (Kawai 1986, Huang and Chen 2004, Yadav and Chang 2014). Survivability from the

prepupal stage to adulthood increase with the increasing level of relative humidity (Kakei and

Tsuchida 2000).

Seasonal Prevalence

The wide variety of plant species consumed by T. palmi allow it to inhabit and survive year-round. Usually, in southern Florida, abundant from September to April (Frantz et al. 1995,

Seal 1997) though population reach peak from mid-November and continue up to the end of

March (M. A. Razzak, personal observation). This thrips begins infestation in the field shortly after planting of host crops in October. In addition, adults from the adjoining infested field easily immigrate to the un-infested newly planted field (Seal 2001). They become more abundant as the plants add new leaves and remain common in the field until after crop maturity (Capinera 2000,

Seal 2011). The vegetable growing season in southern Florida is typically October to May but is followed by the planting of smaller acreages of summer vegetables, which include Thai eggplants (Solanum undatum Walsh) and okra (Abelmoschus esculentus L.). These summer vegetables, ornamental and fruit plants, and wild hosts including weeds serve as reservoir hosts allowing the thrips to survive until vegetable crops are planted for the next growing season in mid-September to October (Seal et al. 1993, Seal and Klassen 1995). Moreover, adults can inhabit in well drained soils with adequate air space (Seal 1997). Warm weather is favorable for population buildup. However, mature host crops are not as favorable as young crops for increasing population. Hence, populations often decline despite existing warm weather (Etienne et al. 1990, Copper 1990, Ho and Chen 1992).

Population Density

A better understanding of the species-specific population dynamics is an inevitable component for sampling protocols and management plans for melon thrips. Population densities of melon thrips are influenced by humidity, temperature, rainfall and the duration of sunshine

(Su et al. 1985, Kirk 1997b, Etienne et al. 1990, Nakata 1995, Kajita et al. 1996). Temperature and rainfall are the most important weather factor which affect thrips populations (Lewis 1973).

Population of T. palmi depressed significantly by rainfall (Etienne et al. 1990, Copper 1990, Ho and Chen 1992, Seal 1997). Seal (1997) reported peak population density in the middle of

November 1991 and remained through the middle of December. Larvae exceeded the number of adults in both fall and spring plantings. Moreover, Number of females was always more than the number of males (Seal and Stansly 2000).

Within-Plant Distribution

Besides reliable identification and detection, information on within-plant distribution of insect pest is essential in the development of tactics and strategies for management. Within-plant distribution also helps to develop a reliable and cost-effective sampling protocols by providing stratum wise density which is an essential component for implementing a successful Integrated

Pest Management (IPM) programs. In addition, plant strata play an important role in feeding location of insects. Within the plants, vertical distribution of thrips adults and larvae of thrips may differ (Reitz 2002, Mo et al. 2008). Greatest density of adult thrips was found on leaves compared to flowers and immature fruits of aubergine, pepper, and cucumber. Moreover, adults were mostly concentrated on the middle leaves before moving to the top stratum. Larval abundance was highest on the lower leaves, on which adults had been present a week before

(Kawai 1983a, 1988b; Rosenheim 1990).

Majority of the adult melon thrips were distributed on the top one third of the green house cucumbers (Nishio et al. 1983), and F. occidentalis on greenhouse sweet pepper (Shipp and

Zariffa 1991). In field grown tomato, flower thrips were mostly concentrated in the upper canopy flowers than the lower (Salguero-Navas et al. 1991). Adults and larvae of onion thrips, Thrips tabaci were distributed in higher number on the middle leaves (Theunissen and Legotowska

1991). Adults and larvae of chilli thrips, Scirtothrips dorsalis, were highly abundant on top most strata followed by middle and lower leaves (Seal et al. 2006). Miyashita and Soichi (1993) noted that most melon thrips adults aggregated at the growing point before flower differentiation and dispersed to other plant parts thereafter. Larvae prefer to feed gregariously specially on older leaves (Tsuchida 1997). In high density population, consistently higher density was found on topmost stratum of potato in Jeju Island, Korea (Cho et al. 2000). Typically, in snap beans, T. palmi infestation begins on the older lower leaves but then moves upward to the middle and upper parts of the plant (Seal and Stansly 2000). Moreover, adult and larval stages of T. palmi occur mainly on the abaxial or ventral surface of most host plant leaves. However, in the greenhouse both adult and larva can be seen on adaxial or dorsal surface (Seal et al. 1993, Seal

1997). Adults and larvae were found on the underside of field-grown potato leaves (Cho et al.

2000).

Insecticide Based Management of Melon Thrips

The high rate of reproduction, short generation time, use of multiple host plant species, and cryptic behavior all contribute to the difficulty in managing T. palmi. As eluded above, its multi-voltinism and diverse host range allow T. palmi to exist throughout the year (Seal and

Stansly 2000, Seal 2011). Moreover, re-infestation of fields by immigration of adults from adjacent fields and nurseries is very common (Seal 2001). As noted, T. palmi eggs are laid inside plant tissues, and the tiny larvae and adults can invade developing buds, flowers, and calyxes of developing fruit: these places are not easily reached by conventional spraying of insecticides

(Cannon et al. 2007b, Kim et al. 2014). Furthermore, pupation in the soil aids in maintaining high population despite the use of foliar insecticides at weekly intervals (Seal et al. 1993).

Chemical, biological, and botanical insecticides are principal management techniques for this

pest, although, over the time, frequent application of foliar insecticides has resulted in reduced susceptibility by Thrips palmi.

Chemicals belonging to pyrethroids, organophosphates and carbamates have only limited effects on this pest (Seal et al. 2013). Widely used insecticides such as azinphos-methyl, methomyl, and oxamyl provided 45-60% reduction of this pest (Seal 1997). Seal et al. (2011,

2013) reported that the highest abundance of T. palmi was found in beans and eggplants in

Miami-Dade County during 1991-1994, but it decreased in subsequent years (1995 – 2008) because of using effective chemical insecticides such as spinosad, spinetoram, chlorfenapyr and formatenate hydrochloride which could provide >90% control. Thereafter, the population pattern of melon thrips was upward from 2008 despite using same chemicals and caused economic losses to crop. Studies by Johnson (1986), Matsuzaki et al. (1986), Kawai and Kitamura (1987),

Kawai (1990b, 2001), Rosenheim et al. (1990), and Young and Zhang (1998) have shown that using chemicals alone is not effective in controlling this insidious pest. As for instance, application of broad spectrum insecticides, such as pyrethroids can lead to higher populations of

T. palmi (Young and Zhang 1998). Moreover, persistent use of broad spectrum insecticides has led to the development of resistance by the targeted pest (Gao et al. 2012), secondary pest resurgence (Jensen 2000a, Gao et al. 2012), non-target effects on beneficial pollinators and natural enemies (Demirozer et al. 2012, Reitz and Funderburk 2012, Seal et al. 2013), contamination of crops and the environment, and human health problems (Mostafalou and

Abdollahi 2013) in addition to the huge costs of insecticides (Arévalo et al. 2009). Furthermore, insect pest management programs based solely on insecticides may cause failure eventually (Seal et al. 2013). Overall, chemical insecticide-based control does not seem to be a viable tactics to manage melon thrips.

Integrated Pest Management (IPM)

Dent (1995) and Kogan (1998) defined integrated pest management (IPM) as “a system that, in the context of the socioeconomic farming system and associated environment and the population dynamics of the pest species, utilizes all suitable coordinated techniques in a compatible manner as possible and maintains the pest population at levels below those causing economic injury”. Components of IPM programs include different control measures; such as biological control agents, resistant varieties, semiochemicals and physical control methods such as trapping, and other barriers; cultural methods such as the use of plastic mulches, cover crops, rouging and manipulation of the crop environment; and targeted pesticide applications at critical times (Van Lenteren 1995, Jacobson 1997, Loomans and Heijboer 1999). Cultural management, considered as a fundamental component of integrated pest management, uses strategic crop production practices that reduce the likelihood of damaging pest outbreaks (Zehnder et al. 2007).

Integrated Pest Management has been recommended to control T. palmi (Kawai and Kitamura

1987, Seal 2004). Among IPM techniques, appropriate cultural control plays an important role in managing T. palmi. However, diagnosis and exploitation of a specific limiting factor which hinder the pest population increase pave the way for a successful management strategy either through cultural control or any other technique. Although invasion of Florida by T. palmi, is not very recent, there is relatively little information on effective IPM control strategies for controlling this pest.

Plastic Mulch and Vegetable Production

Plastic mulch for vegetable production is a standard cultural practice in the southeastern

United States and elsewhere in the world (Castro et al. 1993, Vos et al. 1995, Hochmuth, 1997).

Benefits of using plastic mulches include effective fumigation, increased soil temperature and moisture retention, reduced weed pressure, reduced soil compaction, reduction of infestation by

insect and disease pests, cleaner harvested products, higher crop yields per unit area as well as earlier crop production, and more efficient use of irrigation by reducing the soil evaporation and soil nutrients through reduced fertilizer leaching, and improved nutrient uptake (Emmert 1957,

Lamont 1993, Kasirajan and Ngouajio 2012). Therefore, plastic mulches are attributed to be the corner stone of intensive vegetable production systems (Lamont 1993). Main fresh market vegetables those are grown on plastic mulch include bell pepper, muskmelon, eggplant, slicing cucumber, summer squash, tomato, beans and watermelon (Ngouajio et al. 2008, Nottingham and Kuhar 2016). Transmittance, absorbance, and reflectance of solar radiation by colored and

UV-reflective plastic mulch have a variable influence to change the ambient microclimate of plants grown on such mulches (Ham et al. 1993, Tarara 2000, Lamont 2005).

Plastic Mulch and Insect Pest Management Including Melon Thrips

Specific color and reflectance properties of plastic mulches have the potential to deter or attract insects influencing the vision behavior when visit the plants. Particularly, highly ultraviolet (UV) reflective mulch with their higher reflectance disorient the insects’ normal locomotion, navigation and interactions between the sexes (Loebenstein and Raccah 1980,

Harpaz 1982, Schalk and Robbins 1987, Scott et al. 1989, Greenough et al. 1990, Nguyen et al.

2009). Repellency of aphids by reflective synthetic mulches were observed in sweet pepper

(Black and Rolston 1972), cucumber and squash (Schalk et al. 1979). Snap beans planted on the reflective foil mulch had fewer potato leafhoppers, Empoasca fabae (Harris) (Hemiptera:

Cicadellidae) than on the bare soil (Wells et al. 1984). Setiawan and Ragsdale (1987) found that aluminum foil significantly reduced the numbers of leafhopper Macrosteles facifrons (Stal) on carrots, compared with the bare soil. Consistently fewer aphids were observed on tomato plants mulched with aluminum than the white and black plastic mulch treatments (Schalk & Robbins

1987). Populations of Frankliniella spp. and Sericothrips variabilis thrips were three-fold in the non-mulch tomato than in the aluminum painted mulch, and the black mulch showed intermediate efficacy for controlling thrips populations (Scott et al. 1989).

Greenough et al. (1990) reported that several thrips population including Thrips tabaci and Frankliniella fusca were reduced by 68% and 64%, respectively in tomato and bell pepper and overall 33% in a combined planting of tomato, pepper and tobacco grown in mulch with metalized surface. Number of Frankliniella thrips in tomatoes grown on white plastic mulch was higher than grown on black plastic mulch, aluminum plastic, or bare ground (Brown and Brown

1992). Both entirely or laterally painted aluminum plastic mulch significantly repelled aphids and thrips on tomato (Kring and Schuster 1992). However, aphids, thrips, and silverleaf whiteflies were attracted with white surface (Brown et al. 1988, 1989) and white on black mulch

(Csizinszky et al. 1997). Lower thrips counts were reported on red, black, and highly UV- reflective substrates compared with non-mulch treatment (Matteson et al. 1992).

Silver reflective mulch was superior to white, yellow and black with yellow edges of plastic mulch in reducing aphid population in summer squash (Brown et al 1993). Compared to the bare soil silvery plastic mulch treatments reduced thrips injury in hot pepper by reducing the thrips infestation (Vos et al. 1995). Lower number of aphids and thrips were captured from tomato grown over reflective aluminum mulch compared with the other colored mulches (blue, red, orange, white, and black) (Csizinszky et al. 1995). Both silver spray and silver film reflective plastic mulches were superior to white standard plastic mulch and bare soil in reducing the population of aphid in zucchini squash (Summers et al. 1995). Childers and Brecht (1996) found that the white attracted far more thrips than the yellow traps. They showed that white surfaces reflected light in the violet blue (below 500 nm) range, and this color was highly

attractive to thrips. Antignus et al. (1996) reported that the infestation of cucumbers with sweet potato whitefly, western flower thrips and cotton aphid was significantly reduced when the walk- in tunnels was covered with monochromatic UV absorbing plastic sheets. Aphids were most numerous on the bare soil watermelon compared with the clear, white and black mulch (Farias-

Larios and Orozco-Santos 1997). Csizinszky et al. (1997) found more immature Bemisia argentifolii on tomato plants grown over white and black polythene than the plants grown over aluminum or yellow mulches.

UV wavelengths reflected by silver and aluminum pigments on the plastic mulch apparently repel adult whitefly (Stansly and Schuster 1999). Caldwell and Clarke (1999) noted that aluminum coated reflective plastic mulch efficiently repelled striped and spotted cucumber beetle from both squash and cucumber which was six times less than did in the solid black mulch. In comparison with the white and black plastic mulch treatments metalized UV-reflective mulch significantly reduced the abundance of silverleaf whitefly in staked tomato (Csizinszky et al. 1999). Brust (2000) found that reflective mulches significantly reduced the number of alates landing on pumpkin compared with the black or no mulch. According to Rhainds et al. (2001) reflective mulch significantly reduced density of nymphs of tarnished plant bug per flower cluster of strawberry. Stavisky et al. (2002) observed that UV- reflective mulch consistently reduced the population of F. occidentalis and F. tritici in tomatoes in northern Florida. Silverleaf whitefly adults were successfully managed in pumpkin, cucumber, and zucchini squash by UV reflective mulch in comparison with the bare plot (Summers and Stapleton 2002a; Summers et al. 2004a, 2004b). In another research, Summers and Stapleton (2002b) reported that corn leafhopper, Dalbulus maidis adults were repelled by UV- reflective mulches and were more effective than either foliar or soil applied insecticides. Reflective mulch significantly reduced the

colonization of aphid population on the late season cantaloupe than the other mulches as well as bare ground (Summers and Stapleton 2005). Reitz et al. (2003) noticed a reduction in populations of adult Frankliniella on field-grown pepper plants when using UV reflective silver mulch compared with the standard black mulch. In reducing Frankliniella thrips, greatest effects were obtained from metalized silver reflective mulch (Riley and Pappu 2004). Andino and

Motsenboker (2004), demonstrated that the cucumber beetle population was significantly lower on watermelon grown on the silver reflective and the silver on black plastic mulches in comparison with the selective reflective red and yellow plastic mulch.

Zucchini squash grown over reflective mulch had consistently fewer adult whitefly and aphids compared to the standard black on white mulch (Frank and Liburd 2005). Both living and metalized mulches were more effective than the white mulch in reducing the number of whiteflies on zucchini squash (Nyoike et al. 2008). Simmons et al. (2010) reported that, silver based reflective mulch consistently reduced the incidence of adult sweet potato whitefly, Bemisia tabaci (Gennadius) on watermelon. Summers et al. (2010) found that, tomato plants grown over bare soil harbored higher number of three aphid species, the western flower thrips (F. occidentalis), and the false chinch bug (Nysius raphanus Howard) compared to the plants grown over reflective silver plastic mulch. Riely et al. (2012) noted that, UV- reflective mulch reduced the population density of Frankliniella fusca (Hinds) in field grown tomatoes compared to the black plastic mulch. Nottingham and Kuhar (2016) found significantly less number of Mexican bean beetle, Epilachna varivestis Mulsant in the reflective mulches compared to the black plastic mulch and bare soil.

Like other insect’s melon thrips do discriminate between wave lengths, contrast, or intensities of light (Fukushi 1990). Suzuki and Miyara (1983) reported that the incidence of

melon thrips attacking cucumbers was lowest when they were grown on metalized mirror mulch.

Green houses covered with ultraviolet absorbing vinyl film (UV-A) had 90% less invasion of melon thrips than the green houses covered with common agricultural vinyl film (Nonaka and

Nagai 1983, Kawai, 1986, Murai 2001). Thrips palmi avoids red, black and silver colors and is attracted by white and bright blue colors. However, detracted by the same color when it is reflecting the ultraviolet region of spectrum. (Nonaka and Nagai 1984). Population density of melon thrips in silver film mulched plots was only 27% of that in control plots (Makino 1984,

Suzuki and Miyara 1984). Therefore, using plastic mulches that reflect ultraviolet light may be a promising form of cultural control for managing melon thrips. However, there is little information on the population dynamics of melon thrips on the crops grown on plastic mulches, which are reflective or variously colored, despite the history of plasticulture in the USA dates back to 1948 and have been used commercially for vegetable cultivation since the early 1960s

(Lammont 2005).

Late Season Effect of Mulch on Insect Populations

With the progression of growing season, the effect of mulch color as well as reflectivity on insect populations may be decreased as expanding plant foliage covers the mulch partially or completely. Wells et al. (1984) noted that, although reflective foil mulch was able to repel potato leaf hopper Emposaca fabae (Harris) from snap beans early in the season but later in the season higher population of leaf hopper were observed because of increased canopy size as well as attractiveness of plants grown on reflective foil mulch. Scott et al. (1989) reported that the effectiveness of aluminum reflective mulch in reducing the number of thrips populations generally disappeared compared with the black mulch and bare soil when lower leaves of tomatoes shaded the mulch. Kring and Schuster (1992) stated that aluminum painted reflective plastic mulch were able to control aphids and thrips consistently on tomato foliage. However,

numbers of thrips in flowers were not affected significantly by mulch treatments when fully grownup plants shaded the mulched area. Brown and Brown (1992) found that early season number of thrips were greater on tomatoes grown on white plastic mulch than on tomatoes grown on black plastic mulch, aluminum plastic mulch, or bare ground. Early season differences, however, diminished with time as plants grew and shaded a larger portion of plastic mulch.

Similar results were observed for thrips and aphid populations on various vegetable crops, by several authors (Csizinszky et al. 1995, 1997; Reitz et al. 2003; Diaz-Perez 2010; Summers et al.

2010).

Effect of Mulch on the Growth and Development of Vegetable Crops

Besides affecting the behavior of insects visiting the plants, the radiated energy from various colored mulches also influences on the plant’s vegetative growth and development by modifying ambient air and soil temperature (Decouteau et al. 1989, 1990; Fortnum et al. 1995).

Plastic mulches alter the crop microclimate by changing the soil energy balance (Liakatas et al.

1986, Tarara 2000), resulting in changes the soil temperature that may positively affect plant growth and yield (Diaz-Perez and Batal 2002, Lamont 2005, Ibarra-Jimenez et al. 2006). Plastic mulches contribute to change the root zone temperature which in turn influences physiological processes such as plant growth, gas exchange, and uptake of water and mineral nutrients (Tindall et al. 1990, Dodd et al. 2000). Reflective foil mulch appreciably accelerated the growth and maturity of snap beans and Chinese cabbage than the bare soil (Wells et all. 1984, Zalom and

Cranshaw 1981). Aluminized plastic mulch supported better survival of the tomato seedlings and increased growth compared to the black plastic mulch because of less heat stress and lowered soil temperature (Schalk and Robbins 1987). Summers et al. (2004a, 2004b) observed that plants growing over reflective plastic mulch grew more rapidly than did those growing over non-mulch area, with or without imidacloprid treatment. Vine length of cucumber was longer in most

mulched plots than the bare ground treatment (Soltani et al. 1995, Andino and Motsenboker

2004). Silver reflective mulches impacted on the growth and yield tomato plants modifying the root zone temperature (Cooper 1973, Tindall et al. 1990, Díaz-Pérez and Batal 2002, Díaz-Pérez et al. 2007). Highest plant growth attributes were found in silver reflective mulches and lowest in the black mulches (Díaz-Pérez 2010). In warm environments, however, plastic mulches may create high root zone temperature (RZT) conditions that may be deleterious to growth and yield of vegetables (Diaz-Perez and Batal 2002, Lamont 2005, Ibarra-Jimenez et al. 2007). Black plastic mulches are common in vegetable agriculture, because they increase the soil temperatures by absorbing short wavelength light (400-700 nm); while light reflecting mulches, such as metalized (aluminum infused top, black bottom) and white (white top, black bottom), keep soil temperatures cool, making them more conducive for cooler weather crops (Ham et al. 1993,

Lamont 1993). There is a deviation that, shoot dry weight of tomato was not affected by the mulch (silver, black/black, black/white, white black plastic and paper) treatment (Suwwan et al.

1988). Moreover, growth of tomato plants was inconsistent among aluminum, blue, orange, yellow, white and black mulch treatments (Csizinsky et al.1995).

Effect of Mulch on the Yield of Vegetable Crops

Plastic mulch has impact on yields with providing earlier yields. An aluminum film mulch increased squash yields up to 610% over the un-mulched control (Chalfant et al. 1977).

Wells et al. (1984) found that snap beans planted on reflective foil mulch were larger and resulted in greater yields than plants grown on bare soil. Significantly greatest yields of snap beans were obtained from metalized plastic mulches followed by white plastic, black plastic and bare soil (Nottigham and Kuhar 2016). However, there were no significant differences in the quantity, quality, or earliness of tomato yields among white, black, silver based reflective, and bare ground treatments (Brown and Brown 1992). Scalk and Robbins (1987) reported that,

greatest yields of large and extra-large fruits were obtained from plants grown with aluminum mulch. Marketable yield of summer squash was significantly higher in plants grown on the silver reflective mulch compared to the bare ground (Brown et al. 1993). Csizinsky et al. (1995) reported that increased number of extra-large and marketable tomatoes were obtained from aluminum reflective mulch than those grown on the other colored mulches although the differences were inconsistent. Production of marketable zucchini squash was 80% higher on the silver mulched plots than the non-mulched plots with or without insecticide (Summers et al.

1995). There was no significant difference in squash yield over cumulative 14 harvests between fully aluminum coated mulch and solid black plastic mulch (Caldwell and Clarke 1999).

Csizinszky et al. (1999) reported that, in fall planting, yields of tomato were similar with UV- reflective mulches and white control mulches. However, in spring planting, fruit size and marketable yields were greater on plants with silver on white mulch than on the control black mulch. Delayed and remarkably less viral infection in reflective mulched plots were translated in to 45 and 120% increase in pumpkin yields compared with the black and no mulch treatments

(Brust 2000).

Placement of reflective mulch enhanced productivity of strawberry plants by reducing proportion of damaged fruits (Rhainds et al. 2001). Reflective mulch provided significantly higher yield of zucchini squash, pumpkin, and cucumber than in those grown over un-mulched soil and plot receiving pre-plant application of imidacloprid (Summers and Stapleton 2002a).

Because of larger ears size yields of marketable corn was 1.5 to 2 times greater in reflective plots than from fallow plots (summers and Stapleton 2002b). Yields of marketable cantaloupe and zucchini squash were approximately 9.5 and 12 times higher when grown over reflective mulch in comparison with the bare soil control treatment (Stapleton and Summers 2002, Summers et al.

2004a). Field grown pepper yields were also much higher on the UV- reflective mulches than the other mulch treatments (Reitz et al. 2003, Hutton and Handley 2007). Marketable yields of tomato were increased on the silver reflective mulch (Riley and Pappu 2004). Compared to the bare ground yields of watermelon was higher on the reflective mulch due to increased fruit number. In addition, at the time of first harvest greater number of fruit were harvested from reflective mulched plots than the bare ground (Andino and Motsenboker 2004). Both marketable and total yields of bell pepper were higher on silver mulches and the lowest was on black mulches (Diaz-Perez 2010). Both UV- reflective mulch and heat stripe mulch provided more tomato than the black plastic mulch and there was no significant delayed yield (Riely et al.

2012). Tomato yields were increased on white on black mulch compared to the black mulch treatment (Hanna et al. 1997). Squash yields were increased on white but not as much as on aluminum painted reflective mulch in an Alabama study (Brown and Boyhan 1996), no effect occurred on tomato yields (Graham et al. 1995), and white produced the lowest tomato yields in a 1999 study (Coffey et al. 1999). Fruit number and total fruit weight of eggplant were significantly greater on silver painted mulch than the other colored painted mulches and bare ground in one study site. However, apart from silver mulch blue and white colored mulches produced increased fruit number and total yield in another study site. There were no significant differences among black, red, blue and non-mulch control (Mahmoudpour and Stapleton 1997).

Various plastic film mulches have been effective in providing earlier maturing crops (Summers et al. 1995, Teasdale and Abdul-Baki, 1995).

Accumulation of Mineral Nutrients and Thrips Abundance

Nutritional imbalance can play a role in determining the degree of insect attack, an excess of nitrogen (a key element of thrips diet) and deficiency of potassium can enhance the accumulation of amino acids allowing sucking insects to increase their populations on plants

(Mattson 1980, Marschener 1995, Scott-Brown et al. 2002). Plant tissues containing an abundance of aromatic amino acids, soluble carbohydrates, and proteins lead to intensive feeding by F. occidentalis larvae (Mollema and Cole 1996, Wu et al. 2007). A positive relationship exists between nitrogen contents found in host crops and thrips population increases due to increasing fecundity and fertility (Schuch et al. 1998, Daives et al. 2005). Buckland et al. (2013) reported that, adult onion thrips population were 23 to 31% reduced when nitrogen fertilizer application rate was one third of the standard grower’s rate (402 kg ha-1). However, different levels of nitrogen fertilization did not affect the abundance of Frankliniella thrips species in tomatoes (Reitz 2002).

Morphological Characteristics of Plants and Thrips Population

Various morphological and physiological characters of host plants play an important role in regulating population parameters of an insect species. Scott Brown and Simmonds (2006) found that, Heliothrips haemorroidalis preferred plant species having leaves being smooth one or both surface. On the other hand, leaves with glandular trichome had evade the infestation of the same thrips species. Considerable number of research reported that both morphological and chemical features can directly influence the selection of hosts by herbivorous insects including thrips. Plant morphological characteristics such as hairs or trichomes (van Lenteren et al. 1995,

Pfannenstiel and Turner 1998), crystals (Ruiz et al. 2002), Silica (Moore 1984), waxes and extent of toughness of cuticle (Stevenson et al. 1993) play determining role in host selection. Toxic and repellent compounds also influence in food utilization behavior of herbivorous insects

(Schoonhoven et al. 1998).

Role of Amblyseius swirskii in Biological Control

A generalist predatory mite, Amblyseius swirskii Athius-Henriot (Acari: Phytoseiidae), has become a well-known biological control agent following its introduction to the market in

2005, although it has been used for biological control since 1962 (Messelink et al. 2008, van

Lenteren 2012). It can simultaneously control several pest species including whiteflies, western flower thrips, chili thrips, broad mites, and spider mites in vegetables crops and ornamental plants (Arthurs et al. 2009, Cock et al. 2010, Stansly and Castillo 2009, Dogramaci et al. 2011, van Lenteren 2012, Xiao et al. 2012, Calvo et al. 2015). Blasco et al. (2012) reported that A. swirskii can successfully control the eggs and first instar nymphs of Asian citrus psyllids in the laboratory. Kakkar et al. (2016) found that populations of T. palmi were controlled by A. swirskii in cucumber field in Homestead, Florida. Brodsgaard and Stengaard (1992) and Messelink et al.

(2005) were successful in controlling flower thrips species using other phytoseiid mites including

Typhlodromips swirskii (Athius-Henriot) (now largely accepted as genus Amblyseius). It has also been shown that A. swirskii is a more efficient thrips predator than Neoseiulus cucumeris

(Oudemans) or Amblyseius degenerans Berlese (Acari: Phytoseiidae) that are also commercially available (van Houten et al. 2005, Arthurs et al. 2009, Stansly and Castillo 2009, Reitz et al.

2011, Kakkar et al. 2016). Release of 20-25 A. swirskii per square meter can effectively control melon thrips in green house eggplant (Shibao et al. 2010). In Spain, A. swirskii has been used as a biological control agent in 6000 ha of sweet peppers grown in protected environmental conditions (Calvo et al. 2015). Most of these experiments were conducted in laboratory or greenhouse or semi-field situations.

Effect of Reflective Plastic Mulch on Predatory or Parasitic Insects

Honey bees visits the squash plants more frequently grown on the aluminum or white material than the non-mulched control and black mulch (Moore et al. 1965, Wolfenbarger and

Moore 1968). Simmons et al. (2010) found that abundance of the whitefly predator Delphastus catalinae (Horn) and parasitoid Eretmocerus sp. was not affected by mulch color. Species diversity and density of predatory arthropod did not vary living mulch, synthetic reflective and

standard white mulch (Frank and Liburd 2005, (Nottingham and Kuhar 2016). Aphid parasitism by Aphidius ervi (Haliday) was affected due to UV-reflection form aluminum foil mulch until foliage growth obscured the mulch (Zalom and Cranshaw 1981). In field-grown pepper, UV- reflective mulch had significantly lowered the number of predator Orius insidiosus (Say) compared with the black mulch treatments (Reitz et al. 2003). Little attention has been paid to evaluate the effects of UV-reflective mulch on Amblyseius swirskii in field situations.

Research Objectives

• Evaluate the effectiveness of different plastic mulch treatments in managing melon thrips on vegetable crops. • Determine the within-plant distribution of melon thips in vegetable crops gown on different plastic mulch treatments. • Evaluate the growth and yield response of vegetable crops to different plastic mulch treatments. • Evaluate the effectiveness of combination treatment of different plastic mulches and Amblyseius swirskii in managing melon thrips on field grown vegetable crops.

CHAPTER 2 EFFECTIVENESS OF DIFFERENT PLASTIC MULCHES IN MANAGING MELON THRIPS ON SIX FIELD-GROWN VEGTABLE CROPS IN SOUTHERN FLORIDA

Introduction

Florida is a leading agricultural state for growing vegetable crops in the United States. In

2016, vegetable crops including snap beans, bell peppers, tomatoes, eggplants, squash and cucumbers were grown on 107,000 acres of land and generated approximately 1300 million dollars. Much of this acreage is in southern Florida (USDA/NASS 2018, Freeman et al. 2017).

However, Florida vegetable growers have to combat many destructive native and invasive insect pests. Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), is an invasive pest species in the US that is native to Sumatra, Indonesia (Karny 1925, Johnson 1986). In the United States, T. palmi was first observed in Hawaii in 1982, Puerto Rico in 1986 and Florida in 1990 (Nakahara

1984, Johnson 1986, Sakimura et al. 1986, Seal and Baranowski 1992). Since invading Miami-

Dade County, Florida, T. palmi has been recognized as a devastating pest causing severe damage to nearly all vegetable crops and ornamental plants grown in fields and greenhouses (Faust et al.

1992; Hollinger 1992; Seal and Baranowski 1992, 1993; Seal 1994; Seal and Sabines 2012).

Gregarious feeding of adults and larvae of T. palmi on the cell contents of its host plants often results in bronzing of leaves, stunting of whole plants, and scarring and distortion of the fruit, which lower the total marketable yield (Matsuzaki et al. 1986; Wang and Chu 1986; Kawai

1986, 1990; Tsai et al. 1995; Nagata et al. 2002; MacLeod et al. 2004; Cannon et al. 2007b; Seal et al. 2013). In the absence of effective control measures complete defoliation of its host crops can occur from feeding damage within a week of the onset of infestation (Childers 1997; Seal

1997). In severe instances of high population abundance, feeding and oviposition damage can eventually kill the host plants (Nakazawa 1981, Sakimura et al. 1986, Tsai et al. 1995, Seal et al.

2013). Feeding damage can sometimes lead to 70-90% economic losses (Bournier 1983, Seal

1993, Cardona et al. 2002). Infestation of peppers by T. palmi along with Frankliniella occidentalis (Pergande) in Palm Beach County, Florida, caused over $3.9 million in economic damage (Nuessly and Nagata 1995). A serious outbreak of T. palmi occured in Hawaii on cucurbits, eggplant, pepper, and amaranth spinach (Nakahara 1984). In the tropics, estimated crop losses from T. palmi infestation ranged from 15% for potatoes (Vercambre 1991) to 90% for cucumbers (Cooper 1990). Losses of 50-90% occurred in vegetable crops because of the infestation by melon thrips in Puerto Rico, Guadeloupe, Trinidad, and Tobago (Hall et al. 1993).

In addition to feeding and oviposition damage, T. palmi is a known vector of at least six tospoviruses (Honda et al. 1989, Nagata et al. 2002, Frei et al. 2005, Pappu et al. 2009, Reitz et al. 2011). Overall, growers rated this pest as the highest concern for vegetable production in

South Florida (Seal and Sabines 2012). The high rate of reproduction, short generation time, multi-voltinism, inhabiting on multiple host plant species, re-infestation from nearby sources, cryptic behavior, and pupation in the soil all contribute to the difficulty in managing T. palmi

(Seal and Baranowski 1993; Seal and Stansly 2000; Seal 2001, 2011).

To date, growers use different classes of insecticides as a primary tool to manage this insidious pest. Insecticides belonging to carbamates (methomyl, oxamyl), organophosphates

(acephate, azinphosmethyl), growth regulators, botanicals (azadirachtin), spinosyns (spinosad, spinetoram), neonicotinoids (imidacloprid) and diamides (cyantraniliprole) provided effective control of T. palmi (Seal 2011, Seal et al. 2013). However, because of repetitive foliar application of the same chemicals resulted in reduced susceptibility, limited control was achieved for this pest (Seal et al. 2013). It has been widely reported that persistent use of broad- spectrum insecticides has led to a variety of serious problems. These include the development of resistance by targeted pests (Gao et al. 2012), secondary pest resurgence (Jensen 2000a, Gao et

al. 2012), non-target effects on beneficial pollinators and natural enemies (Demirozer et al. 2012,

Reitz and Funderburk 2012), contamination of crops and the environment, and human health problems (Mostafalou and Abdollahi 2013) in addition to the huge costs of insecticides (Arévalo et al. 2009). Overall, sole dependence on chemical insecticides does not seem to be a viable tactic for managing melon thrips. In addition, considering the increasing market for organic and chemical-free produce, it is important to evaluate alternative integrated management strategies to manage this pest.

Among IPM techniques, appropriate cultural control could play an important role in managing T. palmi. Using plastic mulches is a standard cultural practice for vegetable production in the south-eastern United States and elsewhere in the world (Castro et al. 1993, Vos et al. 1995, Hochmuth, 1997). Effective fumigation, increased soil temperature and moisture retention, reduced weed pressure, and efficient irrigation are some of the important benefits of using plastic mulch (Emmert 1957, Lamont 1993). Moreover, specific color and reflectance properties of plastic mulches have the potential to deter or attract insects by influencing their behavior when they visit plants (Schalk and Robbins 1987, Scott et al. 1989, Greenough et al.

1990, Csizinszky et al. 1999, Summers et al. 2010, Antignus 2014, Tyler-Julian et al. 2015).

Mulch surfaces metalized with microscopic layer of aluminum or silver are highly UV- reflective and have been reported to effectively manage infestation and disease transmission from a wide variety of insects including thrips (Scott et al. 1989, Greenough et al.1990, Brown and Brown

1992, Reitz et al. 2003, Riley and Pappu 2004), aphids (Black and Rolston 1972, Schalk and

Robbins 1987, Csizinszky et al. 1995, Brust 2000), whiteflies (Csizinszky et al. 1997, 1999;

Frank and Liburd 2005; Nyoike et al. 2008; Simmons et al. 2010), striped and spotted cucumber beetles (Caldwell and Clarke 1999, Andino and Motsenboker 2004), nymphs of the tarnished

plant bug (Rhainds et al. 2001), potato leafhoppers (Wells et al. 1984, Setiawan and Ragsdale

1987), corn leafhoppers (Summers and Stapleton 2002b), Mexican bean beetles (Nottingham and

Kuhar 2016) and Asian citrus psyllid (Croxton and Stansly 2014).

Similar to a variety of other insects, melon thrips can discriminate between different wave-lengths, contrast, and intensity of light (Fukushi 1990). Numbers of melon thrips were lowest when cucumbers were grown on metalized mirror mulch (Suzuki and Miyara 1983).

Greenhouses covered with ultraviolet absorbing vinyl film (UV-A) had a 90% reduction in melon thrips invasion compared with greenhouses covered in common agricultural vinyl film

(Nonaka and Nagai 1983, Kawai 1986, Murai 2001). Melon thrips were detracted by reflecting ultraviolet light (Nonaka and Nagai 1984). Therefore, using plastic mulches reflecting ultraviolet light may be a promising form of cultural control.

The history of plasticulture in the United States dates back to 1948 and it has been used commercially for vegetable production since the early 1960s. However, there is little information on the population dynamics of melon thrips in crops grown on reflective or variously colored plastic mulches. There is also very little information on effective IPM strategies for controlling this pest, although it invaded south Florida in 1990. Furthermore, research on the seasonal abundance, population dynamics, and management of melon thrips only has been conducted on single crops in field experiments or using up to four crops in the laboratory. Information about host preferences under field conditions using multiple host crops is largely unknown although this information may be very important for vegetable crop selection and insect pest management.

The purpose of this study was to compare the effectiveness of six mulch treatments (five plastic mulches and a control with no mulch) on the population abundance of melon thrips on six commonly grown vegetable crops. Temperature, humidity, rainfall, leaf trichome density, and

leaf nutrient content were also recorded to assess their effects on the population abundance of melon thrips.

Materials and Methods

Study Area, Crop Varieties, Plastic Mulches, Field Preparation, Plot Design, and Mulch Placement

Experiments were conducted in field research plots at the University of Florida, Tropical

Research and Education Center (TREC), Homestead, Florida, during the Fall of 2015 and 2016, which is the main vegetable growing season in southern Florida. Six commonly grown vegetable crops planted in this study were snap beans (Phaseolus vulgaris L.var ‘Opus’, Fabaceae), cucumber (Cucumis sativus L. var. ‘Poinsett 76’, Cucurbitaceae), yellow squash (Cucurbita pepo

L. var. ‘Straight neck’, Cucurbitaceae), eggplant (Solanum melongena L. var. ‘Santana’,

Solanaceae), pepper (Capsicum annuum L. var. ‘Jalapeño-Tormenta’, Solanaceae), and tomato

(Solanum lycopersicum L., var. ‘Charger’, Solanaceae). The five mulch treatments included: 1)

“Shine N’ Ripe” (1.25 mil Metalized top and black bottom), 2) “ Can-Shine” (1 mil Metalized top and white bottom), “Black” plastic 3) black-on-black (Can-Grow-XSB, 0.6 mil), 4) black-on- white (Can-Grow XSB, 0.9 mil), 5) “White” plastic; white-on-black (Can-Grow XSB, 0.9 mil), and 6) bare soil with no mulch as the control. The mulches are manufactured by Canslit Inc.

Victoriaville, Quebec, Canada, and supplied by IMAFLEX USA Inc.

Plants in this study were grown in Krome gravelly loam soil classified as a loamy- skeletal, carbonatic hyperthermia lithic rendoll, which consists of 67% limestone pebbles (>2 mm) and 33% finer particles (Noble et al. 1996). Plowing of the field was done with a mold board plow (CASE IH agriculture) and then the field was disked using disking machine (Athens

Plow Co Inc., TN, USA). The field was divided into four blocks (replications) each with six 31 m long raised beds. Blocks were separated by 3 m of fallow soil. Each raised bed, prepared with

Kennco superbedders (Kenco Manufacturing Co Inc., Atoka, OK, USA) was 91 cm wide and 15 cm high with 1.83 m between centers. Then, granular fertilizer (N-P-K: 6-12-12) (Loveland

Products Inc., Greely, CO, USA) was applied at a minimum of 1307 kg/ha in two furrows, each

20 cm from and parallel to either side of the seed or transplant row and was incorporated within the top 15 cm of the soil. Halosulfuron methyl (55 g/ha, Sandea®, Group # 2, Gowan Company

LLC., Yuma, AZ, USA) was applied between rows as a pre-emergence herbicide to control weeds. Subsequently, plastic mulch was placed on the beds using a plastic layer (Kennco micro- combo, Kenco Manufacturing Co Inc., Atoka, OK, USA). While placing the plastic mulch, two drip tapes (Ro-Drip, USA) with emitters space 30 cm apart were placed 15 cm apart on each side parallel to the center of each bed for irrigation. With mulches and drip-tapes in place, each bed was then divided into six equal 4.6 m subplots, one for each crop, with a 61 cm non-planted buffer zone between adjacent subplots. The experimental design was two factorials with mulch type as main plots set out in a complete randomized design, each 6-bed main plot randomly split into crops types subplots.

Crop Establishment

The six crops (one per subplot) used in this study were arranged in a completely randomized design for each mulch treatment. Holes (7 cm diam.) for seeding and transplanting were cut into each mulch manually with a metallic hole digger maintaining standard spacing between plants of each crop. Transplants of tomato, eggplant, and Jalapeno pepper were raised in an insect free greenhouse. Five-week-old transplants of tomato, eggplant, and Jalapeno pepper were planted manually within the beds spaced 45 cm and 31 cm, respectively. For crops grown from seed, two seeds of squash and three seeds of cucumber and snap beans were manually seeded 31, 31, and 15 cm respectively. Following germination, squash and cucumber were thinned to one plant and snap beans to two plants per hole. Seedlings of tomato, pepper, and

eggplant were transplanted on the day that of 95% bean, squash and cucumber seeds germinated to develop homogeneous foliage situation for melon thrips adults.

Crop Management

After transplanting, approximately 230 ml of starter fertilizer (20-20-20: N-P-K;

Diamond R Fertilizer Inc. Ft. Pierce, FL) solution (0.75 oz/gal of water), was applied as a drench at the base of each transplant using a back-pack sprayer without a nozzle tip. The crops were irrigated for one-half hour twice daily (9:30 am and 3:30 pm). The drip irrigation system delivered 0.4 G per minute per 30.48 m. Consequently, the total amount of water delivered each day was 0.4×30×2×2= 48 G/28 m2. However, for the first four weeks after planting, irrigation times were reduced to 15 min. to manage water stress problems. Three weeks after planting, liquid fertilizer (N-P-K: 3-0-10; Helena Chemical Co. Alachua, FL) was injected through the drip tubes at 325 L/ha provided 1.6 kg of N2/ha. To control Lepidopteran insects including melonworms and pickleworms, the insecticides DiPel® DF (Bacillus thuringiensis var.

‘Kurstaki’ strain ABTS-351, Valent Biosciences Co., Walnut Creek, CA., IRAC # 11A) and

Xentari® DF (B. thuringiensis var. ‘Aizawa’ Valent Biosciences Co., Libertyville, IL., IRAC #

11A) each was applied at 2.24 kg/ha, three applications each year. To control fungal pathogens, copper hydroxide (Kocide® 3000, BASF Ag Products, Research Triangle Park, NC) at 0.8 L/ha, and 1.75 L/ha of chlorothalonil (Bravo Weather Stik®, Syngenta Crop Protection Inc.,

Greensboro, NC) and Mancozeb (1.681kg/ha, Dithane® DF, Dow Agro Sciences) were used in weekly rotation. Weeds were removed weekly by hand.

Leaf Samples

Both in 2015 and 2016, leaf sampling began three weeks after planting or transplanting all crops and continued weekly until the 8th week. Sampling was conducted by collecting five fully expanded leaves randomly from five plants of each subplot on each type of plastic mulch.

Leaves were selected from the middle third of each plant. Sampled leaves were placed in a one- liter plastic cup with a thrips-proof lid; the cups were marked with the block number, mulch treatment and crop type. All sample cups were transported to the vegetable IPM laboratory at

TREC and leaves were soaked in 75% ethanol for 30 minutes to dislodge the thrips adults and larvae. The leaves were then carefully removed from the cup leaving the thrips in alcohol, which was then passed through a 25-µm grading sieve (325-mesh, USA Standard Testing Sieve, W. S.

Tyler, Inc., Mentor, OH, USA) leaving thrips in the sieve. Residue from the sieve was then rinsed with 75% alcohol into a Petri dish and examined under a stereo microscope (Leica MZ6,

Micro-optics of Florida, Inc., Davie, FL, USA) at 10x to determine the number of melon thrips adults and larvae in each sample (Seal and Baranowski 1992). Melon thrips adults were counted separately as females and males: this was determined by the presence or absence of an ovipositor on the ventral surface of the 9th abdominal segment (Seal and Baranowski 1992). The areas of 10 leaves, on each sampling date for each crop were measured using a leaf area meter (LI-3000C,

LI-COR Biosciences, Lincoln, NE, USA). Number of melon thrips on each leaf was divided by the mean leaf area to translate the abundance per cm2 area of a specific crop. Numbers of thrips in each cm2 area were then multiplied by 25 to convert the thrips number in a unit area for each crop. Thrips densities were compared per 25 cm2 of leaf surface to avoid inconsistencies resulting from varying surface areas among crops and on different sampling dates (Table 2-1).

We selected 25 cm2 as a unit area because the lowest mean area for pepper leaves was about 25 cm2 (on the first sample date).

Leaf Mineral Nutrients

Fully expanded, intermediate age leaves from the middle third of each plant were selected for leaf tissue mineral nutrient analysis. For squash, cucumber and snap beans leaves were sampled 45 days after planting (DAP), however, for eggplant, pepper and tomato leaves were

sampled 53 DAP. One hundred leaves (25 per sub plot × 4 reps) from each of pepper and tomato, 48 leaves (12 per sub plot × 4 reps) from snap bean, and 20 leaves (5 per sub plot × 4 reps) from each of eggplant, squash and cucumber, were collected and placed in to a quart sized plastic bags marked with the type of plastic mulch, and crop, and then brought to the laboratory for further processing. The samples were rinsed in deionized water, then transferred to soap solution (30 ml liquinox + 2,500 ml deionized water) for two subsequent washes. In the next step, the samples were rinsed with deionized water to remove soap solution followed by placing them into an acid solution (30 ml of 12N HCL + 2,500 ml deionized water). Finally, the samples were removed from the solution, rinsed with deionized water, then placed on a table covered with paper towels to remove the excess water. The leaf samples were then placed into an oven set at 50 0C until the dry weight remained constant. The dried leaf samples were then sent to an analytical laboratory

(Agro Services International Inc. Orange City, FL, USA) for analysis of the concentrations of macronutrients-Nitrogen (N), Phosphorus (P), Potassium (K); and micronutrients (B, Cu, Fe,

Mn, Zn).

Trichome Density Estimation

At 50 DAP, three leaves per crop (one leaf per plant) were collected from middle third of each sample plant and cut in-to four 10 mm × 10 mm squares. Trichome density per 1000 μm2 area of each square were evaluated using digital microscope (VHX-5000, Multi-scan,

KEYENCE America). Three 1000 μm2 areas were observed per 10 mm × 10 mm area and there were 12 replications per crop. To accurately count the number of trichomes, each1000 μm2 area was magnified up to 150 X for eggplant, cucumber, squash, tomato, and pepper, and up to 200X for snap beans.

Weather Data

Over the experimental period, monthly weather data (temperature, rainfall, and relative humidity) were obtained from the Homestead station of the Florida Automated Weather Network

(FAWN, http://fawn.ifas.ufl.edu/), which was less than 300 m from the experimental field plots.

Data Analyses

Data were analyzed for the number of adults and larvae and the total numbers (adults plus larvae) of melon thrips. Mean numbers of adults and larvae and total thrips from 25 cm2 leaf areas for each crop and mulch were compared separately. The number of thrips were subjected to a log (sqrt (x) + 0.5) transformation before statistical analyses to meet the assumption of normality. Non-transformed means are reported in the tables. Data were analyzed using mixed model ANOVAs with the fixed effects consisting of sample date, mulch, and crop type and their interactions (PROC GLIMMIX model, SAS version 9.3, SAS Institute Inc. Cary, NC, 2013). In the PROC GLIMMIX model, the method of Kenward-Roger’s was used to estimate degrees of freedom. Replicate and treatment (mulch and crop) were considered as random residuals for repeated measure analyses. Mulch was considered the whole plot with crop as the subplot. For adults, larvae, and total counts of T. palmi in each mulch and crop, when the F- value was significant, differences among means (Least square means) were separated using the Tukey’s

HSD (Honestly Significant Difference) procedure in SAS (SAS Institute Inc. 2013). To simplify comparisons, when an interaction was significant, the comparison of means was analyzed for a given level of the other variable. This process is commonly referred to as “slicing”. All the data were analyzed at the 5% level of significant.

Trichome densities were also analyzed using the PROC GLIMMIX model with one-way

ANOVA. For statistical analyses comparing trichome densities, Jalapeno pepper was excluded because we did not find any trichomes in 1000μm2 area on pepper leaves.

Results

Effects of Mulches and Interactions Between Date and Mulch on the Abundance of Melon Thrips

Adult density

In each year, mulch treatments significantly affected the number of adults (P < 0.0001)

(Table 2-2). Regardless of collection date and crop, silver reflective mulch significantly reduced thrips adult populations compared with the other mulches and the no mulch control treatment throughout each sample period (2015: F = 22.93; df = 5, 18; P < 0.0001; 2016: F = 11.44; df = 5,

18; P < 0.0001). The highest number of adults were recorded from the control treatment and white on black mulch followed by the black mulch treatments (Table 2-3). There was a significant interaction between date and mulch for the abundance of adults (P < 0.0001) (Table

2-2). From the first to fourth sampling dates, metalized mulches significantly reduced the numbers of adults compared with the control and other non-UV reflective mulch treatments (P <

0.05). However, there were no significant differences between the control and the white on black mulch treatments in the resulting number of adults. The black on black and black on white mulches moderately reduced the adult numbers. Moreover, on the fifth sample date of 2015, there were no significant differences among the mulch and control treatments. However, a significant variation occurred among treatments on fifth sample date of 2016, when significantly fewer adults were found in the reflective mulches than in the other treatments (F = 4.80; df = 5,

86.21; P = 0.0006) (Table 2-4).

Larval density

During both years, the abundance of larvae was significantly affected by mulch treatment

(P < 0.0001) (Table 2-5). Regardless of crop and date, differences among the treatments in larval abundances were significant; being lowest in metalized reflective mulches followed by black on

white and black on black mulches but were highest in the control and white mulch treatments

(2015: F = 22.19, df = 5, 15; P < 0.0001; 2016: F = 11.30, df = 5, 18, P < 0.0001) (Table 2-3).

There was significant interaction between mulch and date for the mean numbers of larvae (P <

0.0001) (Table 2-5). In 2015 trial, from first to fourth sampling date, larval density was significantly highest in the control and white on black mulch plots followed by black on black mulch. Consistently lower numbers of larvae were recorded from plots with metalized reflective mulches and black on white mulch (P < 0.0001) (Table 2-6). On the fifth sampling day (49 DAP) there was no difference in larval density among mulch treatments (F = 1.55; df = 5, 61.5; P =

0.19). However, mean larval density in the control and white on black mulch treatments was about 50% more than in the reflective mulches. In 2016, densities of larva were similar to 2015 except on the first two and last (49 DAP) sampling dates. At the high larval population densities lasting from the third sampling date to the last sampling date, significantly fewer larvae were sampled from plants on either reflective mulch than the other treatments (P < 0.0001). Again, significantly highest number of larvae occurred in the white on black mulch and control treatments which was followed by the black on black and black on white mulch treatments

(Table 2-6).

Total numbers of melon thrips

In both years, the total number of melon thrips were also significantly affected by mulch treatment (P < 0.0001) (Table 2-7). Throughout the sampling period, significantly fewer melon thrips were found in each reflective mulch treatments than the other mulches and control treatments. However, between two reflective mulches, mean numbers of thrips were lower in the silver on black mulch than in the silver on white mulch. Thrips number on black on white mulch was intermediate among all the treatments and was very close to the number found on reflective mulches (Table 2-3). The number of total thrips was significantly higher in the control and white

on black mulch than in the other treatments (2015: F = 20.38; df = 5, 18; P < 0.0001 and 2016: F

= 11.86; df = 5, 18; P < 0.0001) (Table 2-3).

In both years, the interaction of mulch and date was significant for total numbers of melon thrips (P < 0.0001) (Table 2-7). In 2015, using metalized reflective plastic mulch led to a significant reduction in number of melon thrips compared with all other treatments on every sampling date except the last sampling date (49 DAP) (Table 2-8). There were no significant differences in the total number of thrips among treatments in 2015, 49 DAP; however, the population was 50% lower in the reflective mulch treatments than in the white on black mulch

(Table 2-8). However, at 49 DAP in 2016, when thrips populations were high, reflective mulches had significantly fewer thrips than on the all other treatments (F = 6.36; df = 5, 72.16; P <

0.0001) which was approximately 60% lower than in the white on black mulch (Table 2-8). In each year, on all five sampling dates, the control without mulch and white on black mulch treatment always had statistically the highest numbers of total thrips although mean numbers in white on black mulch exceeded the number in control treatment. The black on white and black on black mulch showed intermediate effects in reducing the total melon thrips populations.

However, mean numbers were always lower in the black on white mulch than in the black on black mulch treatment (Table 2-8).

Effects of Crops and Interactions Between Date and Crop on the Abundance of Melon Thrips

Adult density

In both 2015 and 2016, there were significant effects of crop on the number of adult melon thrips (P < 0.0001) (Table 2-2). Regardless of collection date and mulch treatment; eggplant, cucumber and squash had highest number of adults followed by snap bean, Jalapeno pepper and tomato in 2015 (F = 127.85; df = 5, 522; P < 0.0001). However, in 2016 significantly

more adults were observed on eggplant than all other crop treatments. Statistically, numbers found on eggplant were followed by cucumber and squash then snap beans, then Jalapeno pepper, with tomato significantly lower than all other treatments (F = 11.44; df = 5, 522; P <

0.0001) (Table 2-9). In both years, date and crop also showed significant interactions (P <

0.0001) (Table 2-2). Across the five sampling dates in both years, there were always significant differences in the number of adults in eggplant, cucumbers with squash generally having higher numbers than snap bean, pepper or tomato. However, eggplant had the numerically highest mean numbers on eight of the 10 sampling dates in both years: all dates except for 28 and 35 DAP, when cucumbers had the highest mean numbers (Table 2-10).

Larval density

In both years, there was a significant effect of crop and interaction between date and crop for the number of larvae (P < 0.0001) (Table 2-5). For numbers of larvae per 25 cm2 leaf areas, there were significant differences among the crops in both years (Table 2-9). In 2015, the highest numbers of larvae occurred on eggplant and bean, followed by squash and Jalapeno pepper with tomato significantly lower than other crops. In 2016, the highest numbers of larvae were on eggplant followed by cucumber, then squash and bean, then pepper, with tomato again significantly lower than the other crops (2015: F = 155.30, df = 5, 90, P < 0.0001; 2016: F =

277.19, df = 5, 90; P < 0.0001) (Table 2-9).

In 2015, weekly sampling results showed that, with little variation, the number of larvae was significantly highest on eggplant, snap bean and cucumber. Except 49 DAP, when larval density on snap bean exceeded cucumber. Moreover, on every sampling date, unlike adult density, larval density on snap bean and Jalapeno pepper was greater than on squash. Tomato had significantly the fewest larvae (Table 2-11). Similar to adult abundance, consistently highest numbers of larvae were recorded from eggplant on every sampling date in 2016 followed by

cucumber. The number of larvae on snap bean was higher than on squash. However, in contrast to 2015, larval density on squash was higher than on Jalapeno pepper. Consistent with adults, the lowest number of larvae were found on tomato. On the last sampling day (49 DAP) in 2016, when thrips populations peaked in all crops, larval density on eggplant was 95- 97% higher than on tomato (Table 2-11).

Total numbers of melon thrips

Not surprisingly, the total number (adults plus larvae) of T. palmi were significantly impacted by crop, and date-crop interaction (P < 0.0001) (Table 2-7). Regardless of sampling date, the total number of melon thrips were highest on eggplant, followed in turn by cucumber, snap bean, squash, Jalapeno pepper, and tomato (Table 2-9). Each year, from the first to last sampling day, eggplant had significantly more thrips than the other crops. Total thrips numbers on eggplant were followed by cucumber and bean. However, the mean number of melon thrips on snap bean outnumbered that on cucumber on the first, second and fourth sampling dates in

2015; the number of larvae on squash and pepper followed the number on snap bean. Again, tomato had the lowest total number of T. palmi (Table 2-12).

Date Effect on the Abundance of Melon Thrips

Adult density

In both years, numbers of adult were significantly influenced by sampling date (P <

0.0001) (Table 2-2). Adult counts were low at the first sampling date in 2015 regardless of crop and mulch, increasing significantly from the second sampling date (F = 58.78; df = 4, 715; P <

0.0001). In 2016, adult abundance did not increase significantly until the third sampling date (28

DAP) and then increased onwards significantly (F = 108.78; df = 4, 715; P < 0.0001) (Table 2-

13).

Larval density

Numbers of larvae were also significantly impacted by collection date (P < 0.0001)

(Table 2-5). Following adult numbers, larvae were significantly lowest on first sampling in both years and intermediate density on the next two sampling dates. Larval density then peaked from fourth sampling and onwards (2015: F = 67.29; df = 4, 712; P < 0.0001, 2016: F = 134.38; df =

4, 715; P < 0.0001) (Table 2-13).

Total numbers of melon thrips

The sampling date effect on the total number was highly significant (P < 0.0001) (Table

2-7). Total counts showed similar trends in both years, being the lowest on first two sampling dates then rising significantly by third sampling date. The population reached its peak on the fourth sampling date increasing by 60% and 676% more thrips than the immediate previous sampling in 2015 and 2016, respectively (2015: F = 67.27; df = 4, 712; P < 0.0001, 2016: F =

134.80; df = 4, 715; P < 0.0001) whereas the fifth sampling date was similar. Over all, mean number of adults, larvae and ultimately overall counts of thrips from the first to third sampling date were numerically higher in 2015 than 2016. However, population abundance became constant by the fourth and fifth sampling dates in both years study (Table 2-13).

Weather Condition

Average temperature, humidity and rainfall was higher during the experiment in 2015 than 2016 (Table 2-14).

Trichome Density

Trichome density per 1000μm2 leaf area was significantly higher in tomato than squash, cucumber and eggplant with the least numbers in snap beans. There were no trichomes per

1000μm2 leaf area of Jalapeno pepper (Table 2-15).

Leaf Mineral Nutrients

Among macronutrients only nitrogen was lower in eggplant than other crops. With a little variation, concentration of all macronutrients and micronutrients determined were almost similar in all mulch and crop treatments (Table 2-16).

Discussion

Mulch Effects

Till to the second sampling date (28 DAP), there was a little variation in melon thrips numbers among the black surfaced plastic mulches and metalized UV- reflective mulches, which might be due to lower counts of melon thrips.

When population size increased treatment effects were more pronounced. The lowest number of melon thrips (adults and larvae, and total number) were observed in reflective mulch treatments. The black mulch had intermediate effect in reducing melon thrips population.

Throughout the sampling period, control and white on black mulch harbored the highest number of melon thrips. These findings are in agreement with the previous reports on Frankliniella spp.,

Sericothrips variabilis, and Thrips tabaci (Scott et al. 1989, Greenough et al.1990, Brown and

Brown 1992, Matteson et al. 1992, Kring and Schuster 1992, Vos et al. 1995, Csizinszky et al.

1995, Stavisky et al. 2002, Reitz et al. 2003, Riley and Pappu 2004, Summers et al. 2010, Riely et al. 2012). Previous reports on the effects of metalized reflective film and UV-light spectrum on melon thrips also corroborate our findings (Nonaka and Nagai 1983, 1984; Suzuki and

Miyara 1983; Makino 1984; Kawai 1986; Murai 2001).

Besides various thrips species, a wide variety of insect species were also controlled by either aluminum or silver infused reflective mulches compared to bare plot or other plastic mulches such as white, black, red and yellow. Repellence of aphids by reflective synthetic mulches were observed in sweet pepper (Black and Rolston 1972), cucumber, squash (Schalk et

al. 1979), hot pepper (Ang et al. 1980), pumpkin (Brust 2000), tomato (Schalk and Robbins

1987, Csizinszky et al. 1995), summer squash (Wyman et al. 1979, Brown et al. 1993), zucchini squash (Summers et al. 1995), and cantaloupe (Stapleton and Summers 2002). UV wavelengths reflected by silver and aluminum pigments on the plastic mulch apparently repelled adult whitefly (Stansly and Schuster 1999). UV reflective mulch significantly reduced the abundance of silverleaf whitefly in staked tomato (Csizinszky et al. 1997, Csizinszky et al. 1999), zucchini squash (Frank and Liburd 2005, Nyoike et al. 2008), watermelon (Simmons et al. 2010), pumpkin, cucumber and zucchini squash (Summers and Stapleton 2002a, Summers et al. 2004a,

2004b). UV-reflective plastic mulch efficiently repelled striped and spotted cucumber beetle from both squash, cucumber and watermelon (Caldwell and Clarke 1999, Andino and

Motsenboker 2004), nymphs of tarnished plant bug on strawberry (Rhainds et al. 2001). UV- reflective mulch had fewer potato leafhoppers, Empoasca fabae (Harris) on snap beans (Wells et al. 1984), carrots (Setiawan and Ragsdale 1987), corn leafhopper (Dalbulus maidis) on corn

(Summers and Stapleton 2002b), Mexican bean beetle, Epilachna varivestis Mulsant on snap bean (Nottingham and Kuhar 2016) and Asian citrus psyllid, Diaphorina citri Kuwayama on orange (Croxton and Stansly 2014).

Ultraviolet- reflective mulch disrupts the ability of thrips to find their hosts, which reduced number of thrips alighted on the plants (Tyler-Julian et al. 2015). Ultra-violet light can affect insect vision behavior, orientation, navigation, feeding, and interactions between the sexes

(Nguyen et al. 2009, Antignus 2014). We did not find much difference in the amount of leaf chemical micro and macronutrients, which could cause variation in the abundance of melon thrips adults or larval population in different mulch treatments. Therefore, our findings and

hypothesis are in agreement with these assumptions that reflective properties of the metalized plastic mulch have the potential to repel insect species including melon thrips.

We found highest number of melon thrips in standard white on black mulch and which also agrees with the previous reports. Thrips palmi avoids red, black and silver colors and is attracted by white and bright blue colors (Nonaka and Nagai 1984). Adult aphids, thrips, and silverleaf whiteflies were attracted to white (Brown et al. 1988, 1989) and white on black mulch

(Csizinszky et al. 1997). White surfaces reflected light in the violet blue (below 500nm) range was highly attractive to thrips (Childers and Brecht 1996).

Numbers of larvae of melon thrips were lowest in the reflective mulches as compared with the control and other non-UV reflective mulch treatments. The reason partially might be due to less number of adults in the reflective mulches and obviously laying fewer eggs. A second theory that can contribute to lower numbers of melon thrips larvae in metalized UV-reflective mulches could be due to reflected intense light, which would have deleterious impact on the egg hatchability or help increased larval mortality. Howard and English (1924) and Miller (1930) found that mortality of Mexican bean beetle eggs, larvae, pupae and adults increased if forced to remain in direct light. To date, there is no information available about direct and continuous light effects on the life stages of melon thrips. In our study we did not quantify the reflected light intensity emitted from various mulches. However, in a recent study by Nottingham and Kuhar

(2016) reported that aluminum coated reflective plastic mulch had high reflected light intensity

(RLI), short wavelength light intensity fluctuated mostly from 300 to 800 μmol photos m-2 s-1.

However, at the end of the season light intensity went down and was less than 300 μmol photons m-2 s-1. RLI in white on black plastic mulch fluctuated from mostly from 300 to100 μmol photons m-2 s-1. Black plastic and bare soil had less than 100 μmol photons m-2 s-1light intensity over the

season. Qian et al. (2016) deduced that hatchability of terebrantian thrips eggs was not affected if exposed to UV-B radiation ≤ 8.7 μW/cm2 continuously for three hours. However, delayed larval development and rate of adult emergence occurred in T. palmi and three other thrips species when exposed to UV-B radiation of ≥ 6.5 μW/cm2. According to the findings of Nottingham and

Kuhar (2016), we can assume that a higher level of reflected light intensity from metalized mulches impacted may have impacted the hatchability of eggs.

At 49 DAP all vegetable crops were in full grown stage and the mulch area was completely covered by squash, cucumber and tomato plants, and partially covered by bean, pepper and eggplant. As the reflectance from reflective mulch was reduced by the shade of the plants the efficacy decreased in reducing the number of thrips, which is evident from the adult numbers. Up to fourth sampling date, the number of adults was lower in the reflective mulches than other treatments. However, on the fifth sampling date, the number of adults were statically similar in all treatments, and the end of study, there were no differences in numbers of larvae among treatments. These results are consistent with previous reports in controlling potato leaf hopper (Wells et al. 1984), aphids (Adlerz and Everett 1968, Wyman et al. 1979), flower thrips and other thrips (Brown and Brown 1992, Kring and Schuster 1992, Csizinszky et al. 1995,

1997; Kirk 1997; Reitz et al. 2003; Summers et al. 2010; Díaz-Pérez 2010) using reflective mulch on different vegetable crops such as tomato, cucumber and pepper.

In 2016, the reflective mulch showed efficacy in reducing the number of melon thrips until the fifth sampling date. This difference from the results of 2015 may have been due to excessive rain in 2015 which caused the partial erosion of silver film and consequently decreased the reflectivity. Moreover, in 2015 mulches were placed in the field two weeks prior to planting.

However, in 2016 mulches were placed in the field three days prior to planting. In addition, there

was 89% more rainfall during the experiment in 2015 compared to 2016 (Table 2-14). The combined effect of rain and dust accumulation resulted in the partial erosion of silver reflective layer from the surface and lead to earlier dulling of the reflectivity of silver reflective mulch in

2015.

Crop Effects

Host plants have significant effects on the life history of insects and same host behaves differently for different species of the same genus. For example, cucumber leaves were more suitable than tomato leaves for F. occiidentalis and F. intonsa based on fecundity, fertility, female longevity and intrinsic rate of increase. However, on cucumber leaves, population increase was higher for F. intonsa than F. occidentalis (Li et al. 2015). Food quality is an important factor, which determines the performance of an arthropod species including development, longevity, and oviposition (van Lenteren and Noldus 1990, Delisle et al. 2015).

This study demonstrated that eggplant was most preferable host for T. palmi followed by cucumber, snap bean, squash and Jalapeno pepper with tomato being the least preferable host.

Broadly, we can speculate that there might be a difference in fecundity, fertility and development of melon thrips in the different hosts we tested in this experiment and melon thrips also might be genetically predetermined to select the most suitable host.

The reason of preference of one host over another may be partially due to differences in volatiles from host plants perceived as odor by insects. The chemical identity of the volatile compounds differs among plant species and among the herbivorous insect species (Mulligan and

Kevan 1973, Paré and Tumlinson 1999). Volatile compounds could be either deterrent or less attractive (Quiroz et al. 1997) or attractants (Feeny et al. 1989) for phytophagous insect species.

The low density of T. palmi in tomato might be due to unsuitability of this crop as a host of this species because of α-tomatine. Hirano et al. (1994) identified α-tomatine as a feeding deterrent in

tomato. Toxic and repellent compounds influence food utilization behavior of herbivorous insects (Schoonhoven et al. 1998). Moreover, Maluf et al. (2007) reported that higher densities of glandular trichomes decreased the distance walked by spider mite and which was considered as indicators of repellence property of tomato cultivar. Plant species possessing glandular trichomes evaded the infestation by Heliothrips haemorroidalis (Bouché) (Scott Brown and

Simmonds 2006). Plant morphological characteristics such as hairs or trichomes play a determining role in host plant selection by arthropods (van Lenteren et al. 1995, Pfannenstiel and

Turner 1998). In our study, trichome density was significantly higher on tomato leaves (68.58 ±

2.46/1000µm2) compared to other crops tested. Therefore, the higher density of glandular trichomes could be another determining factor for less preference for tomato than the other crops used in this study. However, non-glandular trichome number was similar in eggplant, cucumber and squash followed by snap bean (Table 2-15). Trichomes were completely absent in the specified area of ‘Jalapeno’ pepper leaves. Therefore, we assume that leaf surfaces with variable numbers of trichomes might played a role in the selection and host preference of melon thrips.

Morphology, gustatory, and olfactory stimuli of host plants are responsible for final selection and acceptance of hosts (Terry 1997) because antennae and mouthparts of thrips consist mechano- and chemoreceptors (Moritz 1997). Onion cultivars had different level of infestation by Thrips tabaci because of differences in plant architecture and leaf morphology (Coudriet et al. 1979).

In 2015, total number of thrips in snap bean was similar to that in eggplant, whereas in

2016 density (highest to lowest) of total thrips was in eggplant, cucumber, squash, bean,

‘Jalapeno’ pepper and tomato. The reason for the difference might be due to a nearby bean field which was highly infested with melon thrips. Adults might have migrated after harvest (5th

January 2016) and infested bean in the research field and build up population on bean. Adult

density increased dramatically on 28 DAP, from 0.43 ± 0.24/25 cm2 leaf area on 21 DAP to 3.21

± 1.31/25 cm2 leaf area. Seal (2001) reported that adult immigration from adjoining fields is very common. In a laboratory study, Tsai et al. (1995) reported that, larval development and survival was lower on bell pepper as compared to eggplant, cucumber and winter melon. Moreover, the egg production rate decreased if adults fed on bell pepper leaves. Our study also showed that thrips density was highest on eggplant followed by cucumber, snap bean, squash and Jalapeno pepper, which agrees with the report of Kawai (1990) and Tsai et al. (1995). It has been reported that larvae feeding on tomato and strawberry foliage cannot pupate (Kawai 1990).

A joint effect of antixenosis and antibiosis is thought to be important determining factors in host choice, and damage potential by thrips (Leigh 1995, Frei et al. 2003). Population parameters such as fecundity, fertility and immature, and adult survivability were significantly lower in the resistant bean cultivars than in the susceptible cultivars (Frei et al. 2003). Extent of antibiosis of some vegetable crops like cucumber, lettuce, tomato and pepper plants to F. occidentalis was correlated with low concentrations of total aromatic amino acids relative to total leaf proteins (Mollema and Cole 1996). In our study, the vegetable crops tested had same level of nutrients, but these crops might differ in some organic chemical properties, which underlie the difference in host choice by melon thrips. Besides nutritional quality, cell wall (cuticle) structural or compositional variation in tested plants might be another reason for variation in host choice by melon thrips adults. A hard cuticular layer might create a physical impediment for egg laying or scrape the leaf tissue for feeding of both adult and larva. Several species of Lycopersicon showed high or moderate antixenotic effects on F. occidentalis nymphs. Strong antixenotic effect on adult F. occidentalis was due to differences in the structure of internal mesophyll cell (Kumar et

al. 1995). Silica, waxes and extent of toughness of cuticle play determining roles in host selection (Moore 1984, Stevenson et al. 1993).

Variation in the quantity of organic compounds such as phenolics, lignin, phytoalexins in the leaf tissue could be another reason for differences in the number of melon thrips among crops. Higher concentration of these compounds is reported to increase tissue hardness, decrease nutritional quality, digestibility of the cells and ultimately impact on fecundity, fertility and survivability of several sap sucking insect including whitefly, aphids and melon thrips (Correa et al. 2005, Goussain et al. 2005, Aguirre et al. 2007, Almeida et al. 2008). Organic compounds were not measured in crops tested in our study, but they could have played a role in the differences in melon thrips preferences among the crops tested.

Our study data showed that tomato is the least preferable host. However, we found considerable number of larvae on tomato leaves (5-70/five-leaf sample) which partially explains that host switching behavior of melon thrips. Plasticity of host switching is alarming for south

Florida, which is major tomato production area. Thrips palmi has been reported to transmit a watermelon infecting isolate of TSWV in Taiwan and Japan (Yeh et al. 1992, Honda et al. 1989), and therefore could be an economic pest for tomato in south Florida in the future.

Date Effects

An effective and sustainable pest management strategy require knowledge on the seasonal abundance, peak periods of pest attack and estimates of changes in the pest density

(Kakkar et al. 2012). Moreover, success and efficiency of a control measure largely depend on early detection and estimation of pest outbreak and damage potential (Dent 1992). In this study, for the first three weeks of sampling, the population density of T. palmi was lower in the second year of the study than the previous year; presumably due to average temperatures in November of 2016 (21.46 oC), which was lower than November of 2015 (25.25 oC). Moreover, relative

humidity (RH) of the study period in November 2016 (62.31%) was lower than in November

2015 (85.67%). Insects are poikilotherms, so, temperature and humidity independently or combined play an important role in their population dynamics which has been revealed by numerous researchers on insects worldwide. Temperatures affect all aspects of insect biology including growth, courtship, mating and reproduction (Hoffmann et al. 2003). An RH of 70-80% and temperature 25-30 oC temperature were found to be optimum for population growth of melon thrips and can allow completion of 25- 26 generations each year (Kawai 1986, Huang and

Chen 2004, Park et al. 2010, Yadav and Chang 2014). In Brazil, Leite et al. (2006) reported that the mean density of melon thrips on eggplant was higher in Guidoval province with warmer temperature (23.62 ± 1.34 oC) than in Vicosa Province with temperature range of 20-21 oC. In addition, survivability from the pre-pupal stage to adulthood increases with the increasing soil moisture content. A soil moisture content lower than 80% is not suitable for prepupa and pupa

(Kakei and Tsuchida 2000). Another reason for yearly differences could be migration from nearby commercial snap bean field, which was already infested with melon thrips in 2015. That year, grower harvested within two weeks of our crop establishment. However, in 2016 there was no previous reservoir crops except wild hosts and a nursery more than 200 meters away from experimental plot. Seal (2001) reported that adults from the adjoining infested fields easily immigrate to an un-infested newly planted field.

In 2016, from the fourth week of sampling mean population density increased rapidly and exceeded the mean number in 2015 even though the base population was higher in 2015 than

2016. This could be due to less rainfall in the month of December in 2016 than 2015.

Temperature and rainfall are the most important weather factors which affect thrips populations

(Lewis 1973). Average monthly temperature for December was almost same, 23.92 oC and 23.32

oC, for 2015 and 2016. The RH in December were also similar in both years 89.75% in 2015 and

86.90% in 2016. However, rainfall was 9.65 mm more in December 2015 than 2016. Population densities of melon thrips are influenced by humidity, temperature, rainfall and the duration of sunshine (Su et al. 1985). Population of T. palmi decreased significantly due to heavy rains

(Etienne et al. 1990, Copper 1990, Ho and Chen 1992, Kajita et al. 1996, Kirk 1997, Seal 1997) which can wash away larvae and adults from leaves and can kill them by drowning. Moreover, excessive rain can kill immobile and delicate pupae on the soil surface by drowning as result of temporary flooding and by distorting or damaging pupation sites.

Study results also showed that in both years, on all crops and mulches total (adults plus larvae) counts were lower on the first two sampling date followed by third sampling date (35

DAP) and reached peak on the fourth and fifth sampling date. These patterns of population increase might be explained by following facts. Melon thrips require almost three weeks to complete their life cycle at 20-22 oC (Park et al. 2010). After three weeks, a new generation emerges and continues to reproduce resulting rapid increase in population density with progression of season. In addition, with the progression of growth period, plant biomass increases with increasing leaf surface which supports higher thrips population. Seal (1997) also reported that low population density of T. palmi on the first sampling date (2-3 wk old plants) on pod squad bean, potato, and eggplant. In fall planted bean populations of melon thrips peaked 54

DAP. In another study, populations peaked on 37 DAP and continued up to 62 DAP (Seal and

Stansly 2000). Mo et al. (2008) observed similar population abundance fluctuation pattern of onion thrips (Thrips tabaci) on onion with occurring low abundance (≈ 1 egg per plant) when crop was young. However, during the rapid increasing stage egg density become doubled and more than doubled every 7 days and within three months egg density reached >6500/plant.

However, Welter et al. (1990) reported that thrips densities did not reach peak until 63 DAP on cucumber in Hawaii. The reason of this variation might be differences in climatic conditions of two different geographic areas.

Implications and Future Studies

Results of this study demonstrated that growing vegetable crops on the metalized highly reflective silver plastic mulches reduced the severity of melon thrips infestation. However, this research has concentrated on a single aspect of melon thrips management in vegetable crops.

Therefore, this method could be combined with early season application of biorational pesticides and other cultural control methods, as well as biological control techniques to increase the efficacy of an integrated pest management program. However, it is also necessary to explore if planting vegetable crops on reflective mulches provide better growth and yields because metalized reflective mulch is costlier than other commonly used plastic mulches. Moreover, host range and results of the weekly population density study in different crops will help in decision making for treatment schedules to manage T. palmi on the most commonly cultivated crops in southern Florida and other areas with similar growing conditions because prevention of thrips outbreaks is often easier than eradication and control. Finally, to build up a foundation of an effective integrated melon thrips management further studies on year-round seasonal abundance, population dynamics, damage potential and interaction between melon thrips and these hosts need to be explored.

Table 2-1. Crop leaf areas on 10 sampling dates (5 per year) (Mean ± SEM cm2). Year Crop 21 DAPy 28 DAPy 35 DAPy 42 DAPy 49 DAPy 2015 Pepper 24.49 ± 1.13 28.66 ± 1.82 35.08 ± 2.54 36.02 ± 2.43 42.79 ± 2.40 Tomato 29.19 ± 3.03 49.50 ± 4.72 61.51 ± 4.78 58.96 ± 5.47 57.05 ± 5.64 Snap Beans 34.38 ± 2.52 44.27 ± 3.68 64.53 ± 3.21 63.82 ± 3.31 65.40 ± 4.78 Cucumber 82.63 ± 5.69 165.43 ± 13.17 255.70 ± 16.56 289.08 ± 19.88 288.19 ± 17.03 Eggplant 66.67 ± 4.21 197.51 ± 14.99 336.79 ± 26.22 359.91 ± 24.43 329.22 ± 26.25 Squash 131.28 ± 16.16 386.05 ± 23.21 568.58 ± 27.22 493.38 ± 38.20 415.37 ± 29.41

2016 Pepper 24.97 ± 1.53 33.36 ± 1.98 35.54 ± 2.92 36.62 ± 2.63 43.41 ± 2.54 Tomato 44.63 ± 3.90 52.06 ± 5.87 63.14 ± 7.63 58.90 ± 6.80 57.26 ± 7.16 Bean 48.70 ± 3.60 59.19 ± 4.64 70.14 ± 4.08 66.64 ± 4.33 66.16 ± 5.26 Cucumber 98.54 ± 5.36 197.84 ± 7.3 280.14 ± 18.33 303.31 ± 19.69 308.03 ± 17.70 Eggplant 74.19 ± 4.67 215.62 ± 11.70 365.16 ± 21.30 382.38 ± 23.46 374.78 ± 27.52 Squash 137.42 ± 20.62 387.58 ± 30.66 575.25 ± 31.10 505.12 ± 36.10 431.82 ± 29.72 ySample size: n = 10. Days after planting (DAP).

Table 2-2. ANOVA of the effects of date, mulch, and crop on the abundance of adult melon thrips (T. palmi) per 25 cm2 leaf area from six vegetable crops grown on five different plastic mulches and a non-mulch control. Year Effect DF F P 2015 Date 4, 522 154.03 < 0.0001 Mulch 5, 18 22.93 < 0.0001 Date × Mulch 20, 522 6.84 < 0.0001 Crop 5, 90 127.85 < 0.0001 Date × Crop 20, 522 4.44 < 0.0001 Mulch × Crop 25, 90 1.87 0.0067 Date × Mulch × Crop 100, 522 1.10 0.2537

2016 Date 4, 522 383.77 < 0.0001 Mulch 5, 18 11.44 < 0.0001 Date × Mulch 20, 522 4.54 < 0.0001 Crop 5, 90 256.52 < 0.0001 Date × Crop 20, 522 8.25 < 0.0001 Mulch × Crop 25, 90 3.61 < 0.0001 Date × Mulch × Crop 100, 522 1.30 0.0355

Table 2-3. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area in different mulch treatments; sampling dates and crops pooled*. Mulch** Thrips stagez Adult Larva Total 2015 2016 2015 2016 2015 2016 NM 3.3 ± 0.5a 1.4 ± 0.2ab 14.5 ± 1.4a 8.2 ± 1.3ab 16.9 ± 1.6a 9.6 ± 1.4ab WB 3.6 ± 0.5a 1.4 ± 0.2a 12.8 ± 1.5ab 12.2 ± 2.2a 16.4 ± 1.7ab 13.5 ± 2.3a BB 1.5 ± 0.2b 1.2 ± 0.2abc 8.5 ± 1.2bc 9.8 ± 1.8a 10.1 ± 1.2bc 11.0 ± 1.9abc BW 1.6 ± 0.2b 0.8 ± 0.1bdc 6.4 ± 0.8cd 5.1 ± 0.8b 8.0 ± 0.9cd 5.9 ± 0.9bdc SW 1.2 ± 0.1b 0.4 ± 0.1d 5.6 ± 0.7cd 3.0 ± 0.6b 6.8 ± 0.8cd 4.6 ± 0.9cd SB 1.0 ± 0.1b 0.5 ± 0.1cd 4.2 ± 0.5d 3.0 ± 0.5b 5.2 ± 0.6d 3.6 ± 0.6d F; P*** 22.93; 11.44; 22.19; 11.30; 20.38; 11.86; < 0.0001 < 0.0001 < 0 .0001 < 0.0001 < 0 .0001 < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Five sampling dates and six vegetable crops per year and sample size, n = 120. **No mulch (NM), White on black (WB), Black on black (BB), Black on white (BW), Silver on white (SW), Silver on black (SB). *** For each year and each thrips stage, degrees of freedom, df = 5, 18.

Table 2-4. Mean ± SE number of melon thrips adults (T. palmi) from treatments with different plastic mulches and a no-mulch control based on density per 25 cm2 leaf area of six vegetable crops. Mulch Sampling date 21 DAP* 28 DAP 35 DAP 42 DAP 49 DAP 2015 No mulch 2.21 ± 0.80az 6.10 ± 1.81a 3.78 ± 0.67a 1.79 ± 0.32ab 2.76 ± 0.49a White on black 0.96 ± 0.27a 5.44 ± 1.43a 4.07 ± 0.67a 2.63 ± 0.47a 4.85 ± 1.36a Black on black 0.15 ± 0.04b 1.32 ± 0.38b 2.87 ± 0.57ab 1.17 ± 0.18b 2.20 ± 0.39a Black on white 0.15 ± 0.05b 0.85 ± 0.12b 2.92 ± 0.88ab 1.38 ± 0.21ab 2.90 ± 0.52a Silver on white 0.19 ± 0.07b 0.66 ± 0.13bc 1.86 ± 0.49bc 1.33 ± 0.26b 1.85 ± 0.32a Silver on black 0.18 ± 0.05b 0.32 ± 0.05c 0.86 ± 0.19c 1.03 ± 0.19b 2.49 ± 0.45a

Statistics F5,112.6 = 19.60; F5,112.6 = 30.27; F5,112.6 = 10.93; F5,112.6 = 2.84; F5,112.6 = 1.39; P < 0.0001 P < 0.0001 P < 0.0001 P = 0.02 P = 0.23

2016 No mulch 0.15 ± 0.06ab 0.31 ± 0.09a 2.05 ± 0.5ab 2.01 ± 0.40ab 2.41 ± 0.46ab White on black 0.22 ± 0.06a 0.19 ± 0.05ab 1.88 ± 0.30a 2.75 ± 0.50a 1.80 ± 0.33abc Black on black 0.05 ± 0.02b 0.15 ± 0.04ab 1.27 ± 0.35b 1.41 ± 0.25ab 2.97 ± 0.57a Black on white 0.04 ± 0.01b 0.09 ± 0.02ab 0.97 ± 0.18b 1.56 ± 0.36ab 1.56 ± 0.29abc Silver on white 0.05 ± 0.01b 0.06 ± 0.02b 0.40 ± 0.13c 0.73 ± 0.17c 0.97 ± 0.20c Silver on black 0.07 ± 0.02ab 0.07 ± 0.02ab 0.29 ± 0.07c 0.78 ± 0.12bc 1.47 ± 0.36bc

Statistics F5,86.21 = 3.45, F5,86.21 = 3.08; F5,86.21 = 18.46, F5,86.21 = 8.28; P < F5,86.21 = 4.80; P = 0.007 P = 0.01 P < 0.0001 0.0001 P = 0.0006 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Days after planting (DAP).

Table 2-5. ANOVA of the effects of date, mulch, and crop on the abundance of melon thrips (T. palmi) larva per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control. Year Effect DF F P 2015 Date 4, 432 267.16 < 0.0001 Mulch 5, 15 21.19 < 0.0001 Date × Mulch 20, 432 5.96 < 0.0001 Crop 5, 90 155.30 < 0.0001 Date × Crop 20, 432 15.12 < 0.0001 Mulch × Crop 25, 90 0.89 0.62 Date × Mulch × Crop 100, 432 1.37 0.017

2016 Date 4, 432 563.68 < 0.0001 Mulch 5, 18 11.30 < 0.0001 Date × Mulch 20, 432 5.50 <.0001 Crop 5, 90 277.19 < 0.0001 Date × Crop 20, 432 13.58 < 0.0001 Mulch × Crop 25, 90 3.68 < 0.0001 Date × Mulch × Crop 100, 432 1.07 0.33

Table 2-6. Mean ± SE number of melon thrips (T. palmi) larvae in five different plastic mulches and a non-mulch control based on density per 25 cm2 leaf area of six vegetable crops. Mulch Sampling date 21 DAP* 28 DAP 35 DAP 42 DAP 49 DAP 2015 No mulch 15.20 ± 4.73az 7.81 ± 1.31a 13.84 ± 2.96a 17.92 ± 3.22ab 17.73 ± 2.68a White on black 3.71 ± 1.66b 5.16 ± 1.08ab 13.29 ± 2.95a 22.63 ± 4.41a 19.25 ± 3.27a Black on black 2.80 ± 1.25bc 2.56 ± 0.72bc 5.16 ± 1.18 b 16.75 ± 4.06ab 15.37 ± 2.82a Black on white 1.50 ± 0.62c 2.18 ± 0.49c 4.21 ± 0.86bc 10.08 ± 1.97bc 14.04 ± 2.12a Silver on white 1.03 ± 0.36c 1.44 ± 0.38c 4.10 ± 0.98bc 11.08 ± 2.56bc 10.22 ± 1.54a Silver on black 0.93 ± 0.33c 1.57 ± 0.46c 2.17 ± 0.43c 6.39 ± 1.13c 10.12 ± 1.37a

Statistics F5,61.5 = 28.86; F5,61.5 = 15.85; F5,61.5 = 14.15, F5,61.5 = 6.29; F5,61.5 = 1.55; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P = 0.19 2016 No mulch 1.72 ± 0.69a 1.45 ± 0.56a 2.21 ± 0.71a 19.60 ± 4.41a 16.01 ± 3.07bc White on black 1.52 ± 0.77a 1.51 ± 0.47a 1.53 ± 0.40ab 29.69 ± 8.06a 26.64 ± 4.46a Black on black 0.32 ± 0.11b 0.60 ± 0.24ab 1.22 ± 0.38ab 23.44 ± 6.11a 23.30 ± 4.57ab Black on white 0.34 ± 0.15b 0.41 ± 0.18b 0.86 ± 0.28abc 12.50 ± 2.62a 11.16 ± 2.01bc Silver on white 0.61 ± 0.21ab 0.66 ± 0.21ab 0.65 ± 0.18bc 3.17 ± 0.70b 10.03 ± 2.32c Silver on black 0.77 ± 0.29ab 0.82 ± 0.29ab 0.48 ± 0.18c 3.74 ± 0.92b 9.35 ± 1.82c

Statistics F5,92.86 = 5.99; F5,92.86 = 3.77; F5,92.86 = 6.25; F5,92.86 = 17.12; F5,92.86 = 6.68; P < 0.0001 P = 0.004 P < 0.0001 P < 0.0001 P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Days after planting (DAP).

Table 2-7. ANOVA of the effects of date, mulch, and crop on the abundance of total (adults plus larvae) number of melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control. Year Effect DF F P 2015 Date 4, 432 294.19 < 0.0001 Mulch 5, 15 20.38 < 0.0001 Date × Mulch 20, 432 9.09 < 0.0001 Crop 5, 90 176.23 < 0.0001 Date × Crop 20, 432 15.54 < 0.0001 Mulch × Crop 25, 90 1.18 0.28 Date × Mulch × Crop 100, 432 1.11 0.24

2016 Date 4, 432 653.61 < 0.0001 Mulch 5, 18 11.86 < 0.0001 Date × Mulch 20, 432 4.58 < 0.0001 Crop 5, 90 315.80 < 0.0001 Date × Crop 20, 432 13.77 < 0.0001 Mulch × Crop 25, 90 3.88 < 0.0001 Date × Mulch × Crop 100, 432 1.29 0.05

Table 2-8. Mean ± SE number of melon thrips (T. palmi) adults plus larvae in five different plastic mulches and a non-mulch control based on density per 25 cm2 leaf area of six vegetable crops. Mulch Sampling date 21 DAP* 28 DAP 35 DAP 42 DAP 49 DAP 2015 No mulch 17.40 ± 5.20az 13.38 ± 2.71a 17.62 ± 3.29a 19.88 ± 3.32ab 16.11 ± 2.52a White on black 4.67 ± 1.73b 10.59 ± 2.31a 17.36 ± 3.31ab 25.26 ± 4.71a 24.11 ± 4.05a Black on black 2.95 ± 1.26bc 3.88 ± 1.00b 8.04 ± 1.48bc 17.91 ± 4.09abc 17.57 ± 2.93a Black on white 1.65 ± 0.65cd 3.03 ± 0.55bc 7.13 ± 1.40c 11.46 ± 1.98bc 16.94 ± 2.41a Silver on white 1.22 ± 0.38cd 2.10 ± 0.44bc 5.95 ± 1.32cd 12.41 ± 2.70bc 12.07 ± 1.71a Silver on black 1.12 ± 0.35d 1.89 ± 0.48c 3.03 ± 0.48d 7.42 ± 1.23c 12.42 ± 1.67a

Statistics F5,46.68 = 34.93; F5,46.68 = 20.56; F5,46.68 = 14.12; F5,46.68 = 6.12; F5,46.68 = 1.39; P < 0.0001 P < 0.0001 P < 0.0001 P = 0.0002 P = 0.25 2016 No mulch 1.87 ± 0.74a 1.77 ± 0.64a 4.26 ± 1.02a 21.61 ± 4.64a 18.42 ± 3.44abc White on black 1.74 ± 0.82a 1.69 ± 0.51a 3.41 ± 0.60a 32.45 ± 8.36a 28.44 ± 4.68a Black on black 0.38 ± 0.13b 0.75 ± 0.27ab 2.50 ± 0.61ab 24.85 ± 6.25a 26.27 ± 5.02ab Black on white 0.38 ± 0.15b 0.50 ± 0.20b 1.82 ± 0.41ab 14.05 ± 2.91a 12.72 ± 2.24bc Silver on white 0.66 ± 0.21ab 0.73 ± 0.22b 1.05 ± 0.23bc 9.63 ± 2.84b 11.01 ± 2.40c Silver on black 0.84 ± 0.30ab 0.89 ± 0.29ab 0.78 ± 0.22c 4.52 ± 0.97b 10.82 ± 1.96c

Statistics F5,72.16 = 6.39; F5,72.16 = 3.96; F5,72.16 = 11.52; F5,72.16 = 12.42; F5,72.16 = 6.36; P < 0.0001 P = 0.0031 P < 0.0001 P < 0.0001 P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Days after planting (DAP).

Table 2-9. Mean ± SE number of different stages of melon thrips (T. palmi) per 25 cm2 leaf area of six different vegetable crops grown on five different plastic mulches and a non-mulch control (across the sampling period). Crop Thrips stage Adult* Larva* Total* 2015 2016 2015 2016 2015 2016 Eggplant 3.22 ± 0.35az 1.82 ± 0.19a 15.86 ± 1.52a 18.35 ± 2.49a 19.08 ± 1.67a 20.17 ± 2.62a Cucumber 3.63 ± 0.49a 1.46 ± 0.17b 11.16 ± 1.24b 9.90 ± 1.36b 14.79 ± 1.46b 12.51 ± 1.53b Squash 2.73 ± 0.23a 1.49 ± 0.16b 4.66 ± 0.64c 4.80 ± 0.86c 7.25 ± 0.76c 6.29 ± 0.92d Snap Beans 1.62 ± 0.28b 0.69 ± 0.09c 13.98 ± 1.15a 6.49 ± 0.97c 15.61 ± 1.25a 7.18 ± 1.05c Pepper 0.67 ± 0.07c 0.20 ± 0.03d 5.49 ± 0.79c 1.48 ± 0.23d 5.28 ± 0.66d 1.68 ± 0.24e Tomato 0.39 ± 0.03c 0.10 ± 0.02e 0.90 ± 0.10d 0.25 ± 0.06e 1.32 ± 0.12e 0.35 ± 0.06f

Statistics F5,90 =127.85 F5,90 = 11.44 F5,90 = 155.30 F5,90 = 277.19 F5,90 = 176.23 F5,90 = 315.80 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *For each crop sample size, n =120

Table 2-10. Mean ± SE number of adult melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non- mulch control. Crop Sampling date 21 DAP* 28 DAP 35 DAP 42 DAP 49 DAP 2015 Eggplant 1.05 ± 0.37az 2.82 ± 0.68a 3.75 ± 0.58ab 2.53 ± 0.39a 5.92 ± 1.21a Cucumber 0.43 ± 0.16b 5.60 ± 1.97a 5.30 ± 1.10a 2.49 ± 0.36a 4.34 ± 0.50a Squash 1.67 ± 0.76a 1.78 ± 0.30a 3.71 ± 0.45a 2.28 ± 0.20a 4.22 ± 0.42a Snap Beans 0.43 ± 0.24b 3.21 ± 1.31a 1.91 ± 0.27b 1.07 ± 0.17b 1.48 ± 0.15b Pepper 0.09 ± 0.04c 0.81 ± 0.21b 1.02 ± 0.18c 0.65 ± 0.10bc 0.80 ± 0.13c Tomato 0.18 ± 0.06bc 0.48 ± 0.08b 0.67 ± 0.09c 0.31 ± 0.06c 0.31 ± 0.05d

Statistics F5,522 = 27.37; F5,522 = 16.29; F5,522 = 23.47; F5,522 = 26.68; F5,522 = 51.78; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 2016 Eggplant 0.29 ± 0.07a 0.39 ± 0.08a 2.21 ± 0.33a 2.89 ± 0.50a 3.31 ± 0.41a Cucumber 0.12 ± 0.02a 0.18 ± 0.04b 2.04 ± 0.48a 2.17 ± 0.37a 2.79 ± 0.37a Squash 0.12 ± 0.02a 0.19 ± 0.02ab 1.78 ± 0.28a 2.21 ± 0.25a 3.13 ± 0.46a Snap Beans 0.03 ± 0.01b 0.04 ± 0.02c 0.44 ± 0.10b 1.43 ± 0.25b 1.52 ± 0.23b Pepper 0.03 ± 0.02b 0.04 ± 0.02c 0.33 ± 0.08b 0.29 ± 0.06c 0.30 ± 0.05c Tomato 0.01 ± 0.008b 0.04 ± 0.01c 0.06 ± 0.01c 0.26 ± 0.05c 0.13 ± 0.02d

Statistics F5,522 = 25.43; F5,522 = 34.41; F5,522 = 79.52; F5,522 = 61.07; F5,522 = 89.11; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Days after planting (DAP).

Table 2-11. Mean ± SE number of melon thrips (T. palmi) larvae per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control Crop Sampling date 21 DAP* 28 DAP 35 DAP 42 DAP 49 DAP 2015 Eggplant 13.59 ± 4.40az 4.46 ± 0.98b 12.05 ± 2.46a 26.81 ± 3.79a 22.40 ± 2.36a Cucumber 1.27 ± 0.44c 3.70 ± 0.86b 12.02 ± 3.07a 18.85 ± 3.39a 19.94 ± 2.32a Squash 4.51 ± 2.27b 1.35 ± 0.53c 1.94 ± 0.31bc 4.50 ± 0.63b 11.01 ± 1.44c Snap Beans 5.10 ± 1.88b 8.43 ± 1.26a 12.06 ± 1.98a 26.11 ± 3.28a 18.21 ± 1.55ab Pepper 0.20 ± 0.06d 2.09 ± 0.29b 3.59 ± 0.60b 7.43 ± 1.13b 14.15 ± 3.03bc Tomato 0.51 ± 0.21d 0.69 ± 0.17c 1.12 ± 0.27c 1.16 ± 0.29c 1.02 ± 0.14d

Statistics F5,483 = 72.63; F5,483 = 37.20; F5,483 = 37.20; F5,483 = 70.91; F5,483 = 53.81; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 2016 Eggplant 3.81 ± 0.90a 3.52 ± 0.58a 3.66 ± 0.64a 48.46 ± 8.19a 32.27 ± 4.05a Cucumber 0.36 ± 0.09bc 0.93 ± 0.15b 1.41 ± 0.33b 21.54 ± 3.53b 25.52 ± 2.83ab Squash 0.62 ± 0.16b 0.17 ± 0.04c 0.35 ± 0.09d 5.71 ± 0.99cd 17.15 ± 2.98b Snap Beans 0.26 ± 0.06c 0.31 ± 0.08c 1.30 ± 0.35bc 11.66 ± 2.30c 18.93 ± 2.54b Pepper 0.19 ± 0.11d 0.48 ± 0.23c 0.47 ± 0.11cd 3.99 ± 0.77d 2.28 ± 0.46c Tomato 0.03 ± 0.01d 0.05 ± 0.02d 0.03 ± 0.01e 0.76 ± 0.23e 0.36 ± 0.09d

Statistics F5,510.7 = 54.84, F5,510.7 = 48.84; F5,510.7 = 49.74; F5,510.7 = 87.60; F5,510.7 = 128.26; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Days after planting (DAP).

Table 2-12. Mean ± SE number of total counts (adults and larvae) of melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control Crop Sampling date 21 DAP* 28 DAP 35 DAP 42 DAP 49 DAP 2015 Eggplant 14.63 ± 4.72az 7.28 ± 1.54ab 15.81 ± 2.85a 29.33 ± 3.96a 28.32 ± 2.86a Cucumber 1.70 ± 0.53c 9.29 ± 2.72b 17.32 ± 3.54a 21.34 ± 3.63a 24.28 ± 2.61ab Squash 6.18 ± 2.74b 2.59 ± 0.45c 5.65 ± 0.67b 6.78 ± 0.76b 15.05 ± 1.55bc Snap Beans 5.54 ± 2.10b 11.66 ± 2.36a 13.96 ± 2.20a 27.18 ± 3.33a 19.69 ± 1.61ab Pepper 0.28 ± 0.08e 2.87 ± 0.41c 4.61 ± 0.75b 8.08 ± 1.16b 10.57 ± 2.49c Tomato 0.69 ± 0.24d 1.17 ± 0.21d 1.79 ± 0.32c 1.63 ± 0.34c 1.33 ± 0.17d Statistics F5,489.3 = 84.23; F5,489.3 = 30.80; F5,489.3 = 36.37; F5,489.3 = 72.38; F5,489.3 = 70.88; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 2016 Eggplant 4.10 ± 0.96a 3.91 ± 0.65a 5.87 ± 0.82a 51.35 ± 8.46a 35.59 ± 4.39a Cucumber 0.48 ± 0.10bc 1.11 ± 0.17b 3.18 ± 0.71b 29.45 ± 3.37a 28.31 ± 3.05ab Squash 0.74 ± 0.16b 0.36 ± 0.05c 2.13 ± 0.30b 7.92 ± 1.00b 20.27 ± 2.92b Snap Beans 0.28 ± 0.07c 0.34 ± 0.09d 1.74 ± 0.45c 13.10 ± 2.50b 20.45 ± 2.71b Pepper 0.22 ± 0.12d 0.52 ± 0.23cd 0.80 ± 0.17c 4.28 ± 0.81c 2.58 ± 0.50c Tomato 0.05 ± 0.02d 0.09 ± 0.03e 0.09 ± 0.02d 1.02 ± 0.25d 0.48 ± 0.10d Statistics F5,505.3 = 65.67; F5,505.3 = 56.02, F5,505.3 = 65.95, F5,505.3 = 100.56, F5,505.3 = 144.73; P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Days after planting (DAP).

Table 2-13. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of six vegetable crops grown on five different plastic mulches and a non-mulch control; on each sampling date. Sampling Thrips stage y date Adult Larva Total 2015 2016 2015 2016 2015 2016 21 DAP* 0.64 ± 0.15cz 0.10 ± 0.01c 4.19 ± 0.95d 0.88 ± 0.19c 4.84 ± 1.05d 0.97 ± 0.20c 28 DAP 2.45 ± 0.43b 0.15 ± 0.02c 3.45 ± 0.38c 0.91 ± 0.15b 5.81 ± 0.73c 1.06 ± 0.16c 35 DAP 2.73 ± 0.26a 1.14 ± 0.13b 7.13 ± 0.84b 1.16 ± 0.17b 9.85 ± 0.98b 2.30 ± 0.25b 42 DAP 1.55 ± 0.12b 1.54 ± 0.14a 14.14 ± 1.33a 15.36 ± 2.04a 15.72 ± 1.39a 17.85 ± 2.14a 49 DAP 2.84 ± 0.29a 1.86 ± 0.16a 14.46 ± 1.01a 16.08 ± 1.42a 16.54 ± 1.12a 17.95 ± 1.53a

Statistics F4,715 = 58.78 F4,715= F4,712 = 67.29 F4,715 = 134.38 F4,712 = 67.27 F4,715 = 134.80 ; P < 0.0001 108.78 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 ; P < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yOn each sampling date, N=144. *Days after planting (DAP).

Table 2-14. Weekly climate in the study area of the year 2015 and 2016. Month Week Avg. Temperature Avg. Relative Humidity Avg. Rainfall (oC) (RH) (%) (inch) 2015 2016 2015 2016 2015 2016 November 1st 26.82 23.37 85 17.71 0 0.05 November 2nd 25.73 21.54 87.43 79.86 0.02 0 November 3rd 25.61 19.82 88.14 74.14 0.06 0.02 November 4th 22.82 21.11 82.11 78.14 0.19 0.004 December 1st 23.66 24.32 93.85 85.29 1.22 0.008 December 2nd 22.88 23.12 90.57 89.14 0.02 0.1 December 3rd 23.75 23.3 85.57 86.86 0.02 0 December 4th 25.39 22.54 89 86.29 0.36 0.02

Table 2-15. Mean ± SEM number of trichome per 1000μm2 leaf area of different host crops. Crop No. of Trichome Tomato 68.58 ± 2.46az Squash 10.67 ± 0.31b Cucumber 10.42 ± 0.43b Eggplant 10.75 ± 0.35b Snap Beans 4.83 ± 1.17c Statistics F5,13 = 0.03; P < 0.0001 zMean within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

Table 2-16. Percent concentration (ppm) of Nitrogen (N), Phosphorus (P), Potassium (K), Boron (B), Zinc (Zn), Copper (Cu), Iron (Fe) and Manganese (Mn) in the middle stratum leaves of six vegetable crops grown on different mulches. Mulchy and crop Macronutrients Micronutrients Eggplant N P K B Zn Cu Fe Mn SB 2.31z 0.22 1.06 131 17 10.8 234 83 SW 2.81 0.22 1.04 126 17 10.6 176 103 WB 1.90 0.27 0.78 120 14 10.1 209 97 NM 3.21 0.25 2.18 126 17 9.7 233 93 BB 2.75 0.26 2.49 141 17 14.3 136 94 BW 3.65 0.27 2.16 141 14 11.9 156 91

Squash SB 5.22 0.18 0.92 117 19 10.9 197 92 WB 4.03 0.20 1.02 123 19 8.5 121 62

Cucumber SB 3.34 0.36 1.50 296 27 14.7 120 56 WB 3.12 0.36 1.27 165 30 16.7 238 59

Snap Beans SB 4.75 0.37 2.17 151 38 13.6 163 102 WB 3.78 0.26 2.14 137 38 11.7 180 71

Pepper SB 4.52 0.36 0.86 93 11 14.5 189 133 WB 4.50 0.31 0.67 116 12 12.2 142 123

Tomato SB 3.63 0.18 1.34 132 37 13.7 165 95 WB 3.92 0.30 1.02 131 31 11.1 329 77 yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). z concentration assessed in ppm.

CHAPTER 3 EFFECTS OF PLASTIC MULCHES ON WITHIN PLANT DISTRIBUTIONS OF MELON THRIPS, THRIPS PALMI (THYSANOPTERA: THRIPIDAE) IN VEGETABLE CROPS

Introduction

Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), which is native to Sumatra,

Indonesia (Karny 1925, Johnson 1986), is an invasive pest species in the United States. Since invading Miami-Dade County, Florida, in 1990, T. palmi has been recognized as a devastating pest causing severe damage to nearly all vegetable crops and ornamental plants grown in fields and greenhouses (Faust et al. 1992, Hollinger 1992, Seal and Baranowski 1992, Seal et al. 1993,

Seal 1994). Thrips palmi feeds on the cell contents of host plants, which often results in bronzing of leaves, stunting of whole plants, scarring, and distortion of the fruit resulting in reduced marketable yields (Kawai 1990, Matsuzaki et al. 1986, Wang and Chu 1986, Tsai et al. 1995,

Nagata et al. 2002, MacLeod et al. 2004, Cannon et al. 2007b, Seal et al. 2013). Thrips palmi feeding damage can sometimes lead to 70-90% economic losses (Bournier 1983, Seal et al. 1993,

Cardona et al. 2002). Without proper control measures at high T. palmi population densities, complete defoliation of host crops from feeding damage may occur within a week from the onset of infestation and eventually can kill the host plant (Tsai et al. 1995, Childers 1997, Seal 1997).

In addition to the injury and resulting damage from feeding and oviposition, T. palmi is a vector of six tospoviruses (Honda et al. 1989, Pappu et al. 2009, Reitz et al. 2011). Calendar applications of insecticides with different modes of action have been the effective way to manage this pest. Pesticides groups effective against T. palmi included organophosphates, carbamates, botanicals, neonicotinoids, diamides, and spinosyns. However, after 2008, control has been unsatisfactory due to reduced susceptibility to foliar insecticides, which were used frequently (at least once a week) (Seal et al. 1993, Seal 2011, Seal et al. 2013). Therefore, using integrated pest management (IPM) may be an effective, sustainable alternative for managing this economic pest.

Plastic mulch has been found to be an important cultural control technique for use in an IPM programs (Castro et al. 1993, Lamont 1993). Specific color and reflectance properties of plastic mulches have the potential to deter or attract insects by influencing their locomotory and vision behavior (Schalk and Robbins 1987, Scott et al. 1989, Greenough et al. 1990, Csizinszky et al.

1999, Summers et al. 2010, Antignus 2014, Tyler-Julian et al. 2015).

Appropriate, timely and cost-effective sampling is an essential component in developing an effective IPM program. Knowing the biology and behavior of a target pest can help in developing effective plans for sampling. Information on the relative abundance of a pest at different locations on a host plant should be found and clearly communicated to help develop an effective plan for sampling. By determining the best management tool for each pest situation, the resulting information on within-plant distribution can lead to a faster, effective, time-saving and labor-saving sampling. In the present study we investigated within-plant distributions of melon thrips on six commonly grown different vegetable crops at successive growth stages grown on five different plastic mulches and a no-mulch control treatment. Within-plant, vertical distributions of thrips adults and larvae have been reported by many authors. Within-plant distributions of T. palmi have been reported for cucumbers, aubergines, and peppers (Nishio et al. 1983; Kawai 1983a, 1988b; Rosenheim et al. 1990; Miyashita and Soichi 1993; Tsuchida

1997), potatoes (Cho et al. 2000), and snap beans (Seal and Stansly 2000). Salguero-Navas et al.

(1991), Shipp and Zariffa (1991), and Reitz (2002) studied within-plant distributions of

Frankliniella occidentalis (Pergande) on sweet peppers in the greenhouse and on field-grown tomatoes. Similarly, Theunissen and Legutowska (1991) and Mo et al. (2008) investigated within-plant distributions of onion thrips, Thrips tabaci (Lindeman) on onions and Seal et al.

(2006) studied distributions of chilli thrips, Scirtothrips dorsalis Hood, on bell pepper. All of

these studies involved plants grown on beds either non-mulched (bare soil) or covered with black or white plastic mulches. Effects of interactions between different plastic mulches and plant strata on within-plant distributions of thrips have yet to be studied.

Adult and larval stages of T. palmi occur mainly on the abaxial or lower surfaces of foliage on most host plant species grown under field conditions (Cho et al. 2000). However, in greenhouses, adults and larvae can also be found on the adaxial or dorsal (upper) leaf surfaces

(Seal et al. 1993, Seal 1997). Thrips palmi appears to prefer shade instead of direct sunlight.

Mazza et al. (1999, 2002) reported that thrips can sense and respond accordingly to natural and augmented UV-B radiation. In addition, solar or enhanced UV-B radiation may contribute to the reduced survival of insects (Bothwell et al. 1994, McCloud and Berenbaum 1999). Therefore, it is assumed that direct sunlight reflected from different plastic mulches such as metalized UV- reflective mulches can be unfavorable to melon thrips adults and larvae inhabiting the most reflective location, top, middle or bottom strata of their host plants. Previously it was noted that

(in Chapter-2), metalized reflective mulches reduced the number of adults and larvae of melon thrips from the middle third of host plants when compared with the other plastic mulches and a non-mulched control. However, it is not clearly known how the presence or absence of UV- reflective mulch affects thrips distribution on different strata at different growth stages.

Furthermore, very little is known about the nutritional quality of host plants leaves of various strata and its effect on the within plant distributions of melon thrips in different vegetable crops.

Therefore, I studied the within-plant distribution of melon thrips on each six different vegetable crop species at their different growth stages to determine where adult and larval melon thrips could be sampled most effectively and reliably. The investigation included consideration of the effect of UV-reflective mulches and non-UV-reflective mulch, and a non-mulch on adult

and larval melon thrips distribution within different strata of vegetable crops at different growth stages. Quantities of macronutrients (N, P, K) and micronutrients (B, Cu, Zn, Fe, Mn) in leaves from the top, middle and bottom thirds of plants also were determined.

Materials and Methods

The study area, crop species, plastic mulches and their placement, field preparation, plot design, and crop establishment and management were described previously in Chapter 2.

Leaf Sampling and Processing for Thrips and Leaf Area Measurement

To determine the within-plant distributions of melon thrips, plants were divided into three equal sections or strata – lower/bottom, middle, and top/upper based on visual estimation. For the first-time sampling in all crops, fully expanded leaves were sampled from the second node from the bottom (bottom stratum), fourth or fifth node (middle stratum). From the top stratum, expanded but immature leaves immediately below the bud were sampled. For the second sampling when plants were full grown, leaves were sampled from the third node near the bottom, fifth or sixth node in the middle, and second node below the plant apex. This method was used to determine plant strata when sampling snap bean, squash, eggplant, Jalapeno pepper, and tomato.

For vining cucumber plants, foliage within 10 inches from the base (bottom stratum), within six inches from the tip (top stratum), and the section between bottom and top strata (middle stratum) were sampled.

For bean, pepper, and tomato, five plants were randomly selected in each subplot of each mulch treatment, and one leaf was collected from each stratum of each plant. Five leaves were sampled from each stratum per subplot. But, for eggplant, squash, and cucumber, three plants were selected, hence, three leaves were collected for each stratum per subplot. The sampled leaves were then placed in a one-liter plastic cup by stratum marked with crop and mulch type and replication number. All samples were transported to the vegetable IPM laboratory, where

thrips adults and larvae were extracted using methods previously described for Chapter-2. Melon thrips adults and larvae were separately counted using a stereo-microscope at 10X.

To measure leaf areas, 10 leaves for each stratum of each crop representing all mulch treatments were collected randomly then measured individually in the laboratory using a leaf area meter (LI-3000C, LI-COR Biosciences, Lincoln, NE, USA).

Leaf Mineral Nutrient Analysis

Leaf tissue analysis was conducted only for plants on silver on black and white on black mulches on which the highest and lowest number of thrips were observed, respectively (Chapter-

2). Leaves selected for sampling included fully expanded, mature leaves from the bottom and middle strata, and younger leaves from the upper stratum.

The total number of leaves sampled from each stratum were, 100 leaves (25 per sub plot × 4 reps) from each pepper and tomato, 48 leaves (12 per sub plot × 4 reps) from snap bean, and 20 leaves

(5 per sub plot × 4 reps) from each eggplant, squash and cucumber. Leaves collected from the four replicates were placed into a quart plastic bag marked with stratum, plastic mulch treatment and crop species. These were further processed in the laboratory as described in Chapter-2. The leaf samples then were placed in an oven at 50 oC until the samples weight remained constant, then sent to a laboratory (Agro Services International Inc. Orange City, Florida) for tissue macronutrients (N, P, K) and micronutrients (B, Cu, Fe, Mn, Zn) analyses.

Data Analyses

To avoid inconsistencies resulting from varying leaf surface areas among the strata of the same crop and on different sampling dates, thrips densities were compared per 25 cm2 of leaf surface. However, numbers of thrips per entire leaf area were taken into account during data analysis to compare thrips density on the same stratum of a crop but in different mulch treatments.

Data were analyzed independently for adults, larvae and total counts (adults plus larvae).

Thrips counts were subjected to log (sqrt (x) + 0.5) transformation before statistical analyses to meet the assumption of normality. However, non-transformed means and standard errors of the means are presented in the tables. Data were analyzed using mixed-model, two-way analyses of variance with stratum, mulch type and their interactions as the fixed effects (PROC GLIMMIX model, version 9.3, SAS Institute Inc., Cary, NC, 2013). In the PROC GLIMMIX model, the method of Kenward-Roger’s was used to compute degrees of freedom. Replicate and treatment factors (mulch and stratum) were considered as random residuals. Differences among means for each mulch, stratum, and mulch-stratum interaction were separated using Tukey’s HSD

(Honestly Significant Difference) procedure at the 5% significance level.

Results

Leaf Area

Mean leaf surface area of different crops varied on the two sampling dates. For example, on the first sampling, top stratum leaves of Jalapeno pepper were 15 and 20 times smaller than the top stratum leaves of eggplant and squash, respectively (Table 3-1). Leaf surface area from three different strata of a crop were also different. Leaf area of top stratum (11.34 ± 0.59 cm2) of jalapeno pepper was five times smaller than the bottom stratum (59.63 ± 2.27 cm2) leaves (Table

3-1).

Within-Plant Distributions

Within-plant distributions of melon thrips in different crops and mulch types were variable. The effects of strata, mulches, and their interactions on within-plant distributions of melon thrips are presented below for each crop.

Snap Beans

Stratum effects

Melon thrips adults and larvae were found in all strata of snap bean plants (Table 3-2).

On each sampling date (35 and 46 DAP), the adults, larvae and total (adults plus larvae) thrips densities were significantly (P < 0.05) affected by stratum. A greater number of adult and total thrips were found on the top than on the bottom stratum (35 DAP: F = 16.85; df = 2, 36; P <

0.0001; 46 DAP: F = 30.32, df = 2, 36; P < 0.0001). However, at 35 DAP, adult densities at the middle and top strata were not statistically different. Larval densities on both sampling days were significantly higher in the middle stratum than in the bottom and top strata (35 DAP: F = 26.54; df = 2, 36; P < 0.0001; 46 DAP: F = 23.86; df = 2, 36; P < 0.0001) (Table 3-2).

Stratum and mulch interactions

Significant interactions between mulch and plant stratum were observed for adults, larvae and total melon thrips except for adult thrips on the top stratum at 46 DAP (Table 3-4). On both sampling dates, all strata of reflective mulch treatments had significantly fewer adults, larvae and total thrips than the no mulch control and other non-UV reflective plastic mulch treatments.

Although no significant mulch effect was seen on adults at 46 DAP on the top stratum, there were significantly fewer adults on the silver on black mulch at the middle and bottom strata than the white on black mulch treatment (Table 3-4)

Mulch effects

Regardless of stratum, on both sampling dates, significantly fewer adults, larvae, and total melon thrips were found in the silver reflective mulch treatments than in the control and other non-UV reflective mulch (Total number-35 DAP: F = 29.33; df = 5, 15; P < 0.0001, 46

DAP- F = 14.82; df = 5, 18; P < 0.0001) (Table 3-10). Abundance of adults, larvae, and the total

numbers were highest on the white on black mulch and control treatments followed by the black mulch treatments.

Cucumber

Stratum effects

Melon thrips adults and larvae were found on all strata of cucumber plants (Table 3-2).

At 35 and 50 DAP, densities of adults, larvae and total number were significantly affected by stratum (P < 0.05). Regardless of mulch treatment, the number of adult was significantly greater in the middle and top strata than in the bottom stratum (1.6 ± 0.5) on 35 DAP (F = 28.19; df = 2,

36; P < 0.0001) (Table 3-2). However, at 50 DAP, the greatest number of adults were found in the top (8.0 ± 0.89) stratum followed by the middle and bottom strata (F = 60.66; df = 2, 36; P <

0.0001). Larvae were more numerous in the middle and bottom strata than in the top stratum on both sampling dates (35 DAP: F = 49.16; df = 2, 36; P < 0.0001; 50 DAP: F = 29.69; df = 2, 36;

P < 0.0001). The number of larvae in the top stratum was 79% greater at 50 DAP that at 35

DAP. On both sampling dates, melon thrips total number followed the same pattern as larval density (Table 3-2).

Stratum and mulch interactions

There were significant interactions between mulch and stratum on the abundance of melon thrips in cucumber (P < 0.05) (Table 3-5). At 35 DAP, the number of adults, larvae and total melon thrips were significantly (P < 0.05) lower in every stratum of cucumber plants in metalized reflective mulch than the no-mulch control and other plastic mulch treatments. The number of adults, larvae and the total thrips were greatest in every stratum in the standard white on black mulch followed by the no mulch control and black mulch treatments (Table 3-5). At 50

DAP, there were no statistical differences among treatments for the number of adults in the top and middle strata of plants, although average numbers were lower in the reflective mulch

treatments compared to the other treatments. The bottom stratum of metalized reflective mulch treatments still had significantly fewer adult thrips (F = 3.29; df = 5, 53.92; P = 0.01) compared with the no mulch control and other plastic mulch treatments (Table 3-5).

On the top stratum, larval density was significantly lower in the reflective and black on black mulch treatments than in the other treatments (Table 3-5). However, in the middle and bottom strata, treatment effects varied slightly among treatments. Larval density was also greater in the no-mulch and white on black mulch and black on black mulch treatments than in the other treatments. The number of larvae was low in the bottom stratum of silver reflective mulch treatments. Total number of thrips was significantly lowest on the top stratum of reflective mulch treatments and highest in the white on black mulch treatment (F = 3.85; df = 5, 50.98; P =

0.005). However, in the middle and bottom strata of silver on black mulch had the fewest thrips whereas no mulch control and white on black mulch treatments had the highest thrips density, whereas the other treatments had moderate number of thrips (Table 3-5).

Mulch effects

On either sampling date, regardless of stratum, compared with the control and white on back mulch treatments the number of thrips was significantly lowest in the reflective mulch treatments followed by the black on white and black on black mulch treatments (Table 3-10).

Eggplant

Stratum effects

Adults and larvae were present in all stratum of eggplant. However, strata exerted no significant effect on adult abundance at 45 DAP, regardless of mulch type and in spite of 36% and 32% more adults in the middle stratum compared to the top and bottom strata, respectively.

Density of larvae and total thrips were significantly affected by strata. Larvae and total thrips populations were higher on the middle and bottom strata than on the top stratum (Table 3-2). At

60 DAP, there was a significant effect of stratum on adults and larval population densities (P <

0.05). The greatest number of adults were found on the top stratum followed by the middle and bottom (F = 6.60; df = 2, 54; P = 0.003). Larvae and total numbers were significantly greater on the middle stratum than on the top or bottom strata (Table 3-2).

Stratum and mulch interactions

On 45 DAP, no effect of mulch was seen on adult density at the top stratum (P > 0.05) although mean number was 60% fewer in the reflective mulches than the white on black mulch.

However, compared with the no mulch control and other non-UV reflective plastic mulch treatments, significantly lower number of adults were found on the middle and bottom strata of reflective mulch treatments (P < 0.05) (Table 3-6). Similarly, densities of larvae were significantly lower at every strata in silver reflective mulch treatments compared to the control and white on black mulch treatments (P < 0.05). Except for the top stratum, total number of thrips was also significantly reduced in number in the reflective mulches which was four times less than the white on black mulch. At 60 DAP, thrips densities of all stages in all strata showed no significant differences among treatments except for adult abundance on the bottom stratum

(Table 3-6).

Mulch effects

At 45 DAP, regardless of stratum of eggplants, mulch showed significant effect on the adult, larval and total thrips densities (P < 0.05). Compared with the white on black mulch treatments significantly lowest numbers of adults, larvae and total thrips were recorded from the reflective mulch treatments (Table 3-11). At 60 DAP, compared to the control treatment significantly fewer adults were present in reflective mulch followed by the other mulch treatments (F = 3.76; df = 5, 54; P = 0.005). Larval density was marginally affected by mulch treatments and there was no difference between the control and reflective mulch treatments.

Significantly more larvae were present in the white on black mulch followed by both black mulch treatments (F = 2.51; df = 5, 54; P = 0.04). Total thrips density did not vary among treatments (F = 2.42; df = 5, 54; P = 0.06) (Table 3-11).

Jalapeno Pepper

Stratum effects

Adults and larvae were observed on all strata of pepper plants. Regardless of mulch, plant strata had a significant effect on the distribution of T. palmi larvae and total number (adult + larva) on each sampling date (Table 3-3). At 42 DAP, the number of larvae and total thrips were significantly greater on the top and middle strata than on the bottom stratum (Larva: F = 24.85; df = 2, 36; P < 0.0001 and Total number: F = 30.16; df = 2, 36; P < 0.0001). Similarly, adult abundance at 54 DAP did not differ among strata (F = 0.75; df = 2, 36; P = 0.48). However, significantly higher number of larvae and total number of thrips were recorded from the middle stratum than on the top or bottom strata.

Stratum and mulch interaction

On either sampling date, mulch did not have a significant effect on the distribution of melon thrips adult and total thrips in the top and middle strata of plants. However, significantly fewer adults, larvae and total number of thrips were seen on the bottom stratum of metalized mulch treatments than in the no mulch control and non-metalized mulch treatments (Table 3-7).

At 54 DAP, fewer larvae were recorded from the top and bottom strata reflective mulch treatments. Mean number of total thrips was also lowest on every strata of reflective mulch treatments. On each sampling date, every stratum, with few exceptions, greatest mean numbers of adult, larva and total thrips were seen in white on black mulch treatment followed by the black surfaced mulch and no mulch control treatments (Table 3-7).

Mulch effects

At 42 DAP, independent of stratum, mulch treatments showed consistent effects on abundance of every stage of thrips (P < 0.05) (Table 3-11). Fewest adults and larvae were observed in reflective mulch treatments. The number of both adults and larvae were higher on white on black mulch than the control and other treatments (Table 3-11). However, the total number of thrips were consistently lower in the silver reflective mulches than the control and other non-metalized mulch treatments (F = 4.57; df = 5, 18; P = 0.007). The distribution patterns at 54 DAP were similar to those observed at 42 DAP (Table 3-11).

Squash

Stratum effects

Stratum had a significant effect on the distribution of melon thrips early in the season (30

DAP) (P < 0.05) (Table 3-3). A greater number of adults were observed in the middle stratum (F

= 122.86; df = 2, 36; P < 0 .0001) followed by the bottom and top strata (Table 3-3). However, the population density of larvae was prominent on the bottom stratum and no larvae were found in the top stratum (F = 168.44; df = 2, 36; P < 0.0001). The total number of thrips (adult + larva) were significantly greater on the middle and bottom strata than on the top stratum (F = 133.72; df

= 2, 36; P < 0.0001) (Table 3-3). At 50 DAP, contrast to 30 DAP, significantly more adults were found on the top stratum than the bottom or middle strata (F = 59.27; df = 2, 36; P < 0.0001).

The opposite was true for larval distribution; highest and lowest number of larvae were consistently recorded from the bottom and top strata, respectively (Table 3-3). Overall, bottom stratum had significantly largest number of total melon thrips followed by middle and top strata

(Table 3-3).

Stratum and mulch interactions

Mulch and stratum had significant interactions only on 30 DAP sampling (P < 0.05). At

30 DAP, no significant effects of mulch were seen in adult population density on the middle and bottom strata. Nevertheless, the bottom stratum of metalized reflective mulch treatments had

73% and 82% fewer adults than the control and white on black mulch treatments, respectively

(Table 3-8). Fewer adults were present in the reflective and black on white mulch treatments (F

= 2.96; df = 5, 39.2; P = 0.02). No larvae were seen on the top stratum. Numbers of larvae were very few on the middle stratum with no statistical variation among treatments although mean number was 93% more in the no mulch control treatment than in the reflective mulch treatments

(Table 3-8). The largest numbers of larva were observed on the bottom stratum and varied significantly among treatments with lowest number in reflective mulches and black on white mulch (F = 4.88; df = 5, 41.36; P = 0.001) and highest in the white on black and black on black mulch. Total numbers of thrips were highest in white on black mulch followed by black on black and control treatments (Table 3-8). At 50 DAP, when the plant canopy shaded the mulch, there were no significant differences in the number of adults and larvae and, ultimately total counts of melon thrips on different strata of squash grown over different mulch and no-mulch control treatments. Only the number of adults varied slightly in the middle stratum (P = 0.01) (Table 3-

8).

Mulch effects

Early season sampling conducted at 30 DAP showed that adult population density was significantly lowest in the silver on black reflective mulch treatments, whereas, the adult population density was highest in the white on black (F = 3.07; df = 5, 15; P = 0.04) (Table 3-

12). Larval abundance did not differ among treatments and total number of melon thrips

followed the same pattern. In the late season sampling (50 DAP), mulch did not show significant effect on melon thrips adult or larval populations (P > 0.05) (Table 3-12).

Tomato

Stratum effects

Adults and larvae were found on all strata of tomato plants although within-plant distribution of adults and larvae did not vary significantly among strata at 40 DAP (Table 3-3).

Significantly more adults were found at 40 DAP on the top and middle strata than on the bottom stratum (F = 17.26; df = 2, 36; P < 0.0001). Total numbers were significantly higher on the top stratum than the middle or bottom strata (Table 3-3). In the second sampling on 50 DAP, significantly more adults were observed on the top stratum followed by middle and bottom strata. Significantly more larvae were recorded from the bottom stratum than the other strata. The total number of thrips did not vary among strata although the mean number was highest in the top stratum followed by the bottom and middle strata (Table 3-3).

Mulch and stratum interactions

On either (40 DAP and 50 DAP) sampling days, there were no significant interactions between mulch and stratum except the number of larvae and total thrips on 40 DAP sampling. At

40 DAP, there were little variation in the abundance of larvae and total thrips on the bottom stratum (Table 3-9).

Mulch effects

On both sampling days, regardless of stratum, mulch treatment did not have a significant effect on the number of adults, larvae or total thrips (P > 0.05). However, the mean number was lowest in reflective mulches and highest in the white on black mulch followed by black mulch and control no mulch treatments (Table 3-12).

Leaf Mineral Nutrients

Except for manganese there were no great difference in the amounts of leaf mineral nutrients of different strata of six crops tested and between silver on black mulch and white on black much (Table 3-13 and Table 3-14).

Discussion

Mulch Effects

Irrespective of stratum, in every crop overall metalized reflective mulches had significantly lowest number of T. palmi than control and other plastic mulches. This information agrees with the findings of Scott et al. (1989), Greenough et al. (1990), Vos et al. (1995).

Significantly highest numbers of thrips were found in standard white on black mulch followed by the control no-mulch and black surfaced mulch, which also documented by Nonaka and Nagai

(1984), Csizinszky et al. (1997), Brown et al. (1988, 1989), Reitz et al. (2003), Riely and Pappu

(2004). In the late season sampling of cucumber, squash, eggplant, and tomato, there was no significant difference in the abundance of melon thrips among reflective mulches and non- metalized mulches, and no mulch control treatments. The reason might be the reduction of reflectivity from reflective mulches as full-grown plants shaded the mulch area partly or completely. Our results are in agreement with the previous reports in controlling potato leaf hopper (Wells et al. 1984), aphids (Adlerz and Everett 1968, Wyman et al. 1979) flower thrips and other thrips (Kring and Schuster 1992, Brown and Brown 1992, Csizinszky et al. 1995, Kirk

1997, Reitz et al. 2003, Summers et al. 2010, Diaz-Perez 2010) using reflective mulch and other colored mulches on different vegetable crops such as tomato, cucumber and pepper.

Stratum effects

Results of this experiment demonstrated that the distribution pattern of melon thrips adults and larvae were not similar in six vegetable crops. That is not uncommon because microhabitat preference is an intrinsic characteristic of an organism and partially determined by extraneous environmental factors (Taylor 1984). Thus, vertical thrips distribution have been shown to differ in several different host plants. For example, of F. occidentalis differed significantly within nectarine orchards, with more adults occurred at lower levels than at higher levels in the canopy (Pearsall 2000). More adults of F. occidentalis were found in the middle section of cotton plants than the top and bottom strata (Atakan et al. 1996). Osekre et al. (2009) found that, F. tritici adults and larvae were more abundant on the upper canopy leaves than the middle and lower canopy leaves of cotton plants.

Distribution pattern of adults and larvae differed significantly. Within-plants, spatial distribution of thrips adults and larvae may differ (Reitz 2002, Mo et al. 2008). In the present study, with slight variations higher number of adults were found in the top or middle strata than the bottom stratum. Similar results were reported by Nishio et al. (1983) and Kawai (1988b) for cucumber and eggplant, Cho et al. (2000) for field grown potato. Salguero- Navas et al. (1991) and Reitz (2002) also found more adults of Frankliniella spp. in tomato flowers of the upper part of the plant canopy than in the lower part. Frankliniella occidentalis (Pergande) adults aggregated on topmost canopy of greenhouse sweet pepper (Shipp and Zariffa 1991). Adults of chilli thrips, Scirtothrips dorsalis, were highly abundant in the top most strata followed by middle and lower strata leaves (Seal et al. 2006).

In the late season sampling when plants are fully grown, except tomato, number of adults in other crops increased in the top stratum with higher percentage as compared to the middle and bottom strata. For example, adult numbers in the top stratum increased by 43% and 83 %,

respectively in squash and eggplant. At the end of the season when intermediate aged leaves become hard and senesced and food source become depleted in the lower stratum leaves then immature and tender leaves might be the best alternative. This idea could be emphasized by the observation of larval number in the bottom and top strata. In eggplant, larval numbers decreased about 58% in the bottom leaves whereas increased about 84% in the upper stratum leaves compared to early season. Similarly, for squash, in the top stratum adult and larval density increased by 83% and 100%, respectively as compared to the early season sampling. Larval number did not increase in the bottom stratum of cucumber. Moreover, except manganese and iron, percent concentration of macronutrients and micronutrients were almost same in the top, middle and bottom strata. If the leaf nutrition quantity was not a factor, then tissue toughness probably be an important factor which created this variation. Seal (2001) noted that, in eggplant

T. palmi infestation began on the older, lower plant leaves but moved upward to the middle and top of the plant. However, Tsai et al. (1995) reported more adults on matured leaves of eggplant.

But, they did not mention when sampling was done and whether density evaluated from a unit area or not.

It was expected that corresponding to the number of adults, larval numbers would be greater in the top and middle strata. However, contrary to this expectation, highest number of larvae were observed in the middle and second highest in the bottom stratum. The reason might be due to adult flight just in the top stratum of the host plants (Brødsgaard 1998, Gillespie and

Vernon 1990) then migrated to the middle portion for egg laying. Middle stratum is cooler exposed to less UV-light and predators. This environment may be more suitable for egg laying and feeding for offspring and adults. Thrips are able to test the suitability of host plants by dint of both gustatory sensory organ and chemoreceptor in their stylet and antennae (Terry 1997,

Moritz 1997). Onion thrips, Thrips tabaci (Lindeman) laid a greater proportion of eggs on the intermediate ages leaves than the outermost or innermost leaves of onion (Mo et al. 2008).

Simons (1994) and Frank and Liburd (20005) found most of the whitefly immatures and eggs on the bottom stratum leaves of various crops including squash.

Another reason, we can speculate that thrips are cryptic, shade loving and avoid the direct light by staying on the underside of the leaves. Therefore, after emergence from the middle stratum leaves larvae could disperse to the lower stratum which is more protective from sun light, wind and rainfall, and easier to drop to soil for pupation. Chu et al. (1995) and Liu and

Stansly (1995) noted that leaves of lower plant strata offer increased protection from pesticides, natural enemies, and rainfall, wind and extreme temperature. This assumption could be substantiated by the amount of micronutrient and macronutrient in the leaves of three strata. We did not find any great difference in the amount of micro and macro nutrient elements in the leaves of three strata (Table-13 and Table-14). Moreover, with the progression of plant growth, top leaves become full grown middle stratum leaves. Therefore, we cannot exclude the assumption of laying eggs on the topmost young leaves after settling. Thrips are fond of young leaves (Ananthakrisnan 1993). Upper canopy leaves are succulent which may support more thrips than lower senesced leaves. To be ascertain, choice test in laboratory with leaves of tree strata is needed because published literature is not available in this regard. However, notion of initial flight on top most leaves contradict with the finding of Seal and Stansly (2000). They stated that, in snap beans, invariably, melon thrips infestations began on the lower leaves, and with the progression of season, populations moved to the middle and upper leaves.

Overall, middle stratum supported more thrips followed by the bottom and topmost strata.

Again, middle section leaves might be qualitatively more supportive for T. palmi. Previous

studies revealed that increased nitrogen fertilization results in higher populations of F. occidentalis in tomato (Brodbeck et al. 2001) and chrysanthemum (Schuch et al. 1998). Though,

Reitz (2002) did not find significant impact of different rates of nitrogen fertilizer on the abundance of F. occidentalis on tomato. In this study, qualitative variation of organic compounds still unexplored. Brodbeck et al. (2001) reported that F. occidentalis, especially females, were attractive to higher levels of the primary aromatic amino acid phenylalanine. Higher overall levels of aromatic amino acids tend to increase the rate of development of F. occidentalis larvae

(Mollema and Cole 1996). The phenotypic and qualitative difference between young and old leaves have substantial impacts on the oviposition, growth and development of insects (De Kogel et al. 1997 a, b).

Contrary to the other crops, the number of larvae in jalapeno pepper were higher in the middle or top strata than the bottom strata which corresponded with the report of Seal et al.

(2006). He found that the larvae of chilli thrips, Scirtothrips dorsalis, were highly abundant on top most strata followed by the middle and lower strata leaves. Only in tomato, larvae were higher in the bottom stratum than the middle and top strata which is similar to the reports of

Salguero-Navas et al. (1991) and Reitz (2002).

Mulch and Stratum Interactions

In non-vining small size plants like snap bean and jalapeno pepper, with few exceptions, bottom stratum of metalized mulch treatments had statistically, and other stratum had numerically the least number of adults, larvae and total number of thrips. In Jalapeno pepper, on both sampling days, mulch effect was not statistically different in the middle and top strata; however, mean number of adults, larvae and total number were lowest in the bottom stratum of metalized reflective mulches. In snap bean, abundance of all stages of thrips were lower in the reflective mulches except for adult abundance on the top stratum in the late season. Moreover,

the top stratum of reflective mulch had 50% fewer adults than the control or white on black mulch. These results could be interpreted by the effect of UV reflection from metalized mulches, which has reduced the number of adults by deterring them and resultantly reduced the numbers of larvae. Moreover, continuously emitted UV-light might be affected the egg hatchability or larval survivability or displaced the larvae after hatching. These assumptions could be substantiated by the leaf chemical nutrient profile of different strata. Chemical nutrient (macro and micro) analysis of leaves of different stratum of snap bean and pepper grown on different mulch treatments showed no much difference in their amount (Table-13 and Table-14).

Moreover, fully grown up plants (width: snap bean-10.28 cm and jalapeno pepper-6.08 cm) did not cover the mulch area completely till late season. Therefore, reflective properties of the metalized mulches were effective and impacted on the abundance of thrips on all strata and predominantly in the bottom stratum.

Cucumber is a vining plant that, on first sampling (35 DAP) when plant width was about one third of the mulch area of the bed, the lowest number of melon thrips of all life stages were found on all strata of metalized mulches. Suzuki and Miyara (1983), Makino (1984), Suzuki and

Miyara (1984) also reported reduced numbers of thrips on metalized mirror mulch. However, nothing has been reported on mulch stratum interaction effects. End season sampling at 50 DAP showed that the adult abundance become statistically similar in all mulches specifically in the top and middle stratum. The reason might be fully grown-up plants (17.32 cm vine length) shaded the mulched area entirely and diminish the reflection from mulches which is supported by Kring and Schuster (1992) and Summers et al. (2010). However, larval population at 50 DAP was significantly less at all the stratum of reflective mulches and black on white mulch, which could be interpreted by the earlier least population in those mulches. Mean number of adults and larvae

were always lower in reflective mulches than the control and other mulch treatments. Compared to first sampling (in the mid-season) in the second sampling (in the late season) larval abundance at the bottom stratum increased many folds in the reflective mulches however abundance decreased in the control and other mulch treatments. Depletion of food in the bottom stratum leaves of control and non-UV- reflective mulches could be the reason of larval population decrease. However, bottom section leaves were more green and healthy than the other treatments. Moreover, plants were dead ten days later than the plants in the other treatments and dry biomass were highest in the reflective mulches (Chapter 4). Therefore, availability of abundant food might be the reason of larval population increase late season on metalized mulch treatments.

In eggplant, on first sampling date (45 DAP) when plants did not cover the mulched area

(plant width 5 to 6 cm), fewer adults were seen in the middle and bottom strata of plants on metalized mulches. Adult abundance did not differ among mulch types on the upper most leaves.

However, larval number was lowest on the all strata, which can be interpreted as a response to

UV- reflection form metalized mulches which deterred adults. It is usual to expect fewer larvae in the bottom and middle section because the number of adult was already less in these sections.

Number of larvae is positively correlated with the number of adults. However, on the top most layer number of larvae was less because adult number was numerically less in the metalized mulches though did not differ statistically. Total counts were also significantly lowest in the middle and bottom sections. As the number of adult and larvae were lowest in those sections of the both metalized mulches, so it is also usual to be expected that lowest total counts will occur in top strata of silver on black mulches. Sampling on 60 DAP when plants covered most of the area of the mulch (width 22-30 inches) showed that mulch had no impact on the controlling of

thrips on the different strata as well as overall abundance irrespective of stratum. These results strongly indicate that UV- reflection from reflective mulches might be the reason fewer melon thrips in reflective mulches.

In first sampling (30 DAP), when plants were still small (width 9-10 cm), a mulch effect was detectable but not sufficient to be statistically significant in the bottom stratum of plants on reflective mulches. However, at 50 DAP when plants are in fully grown (plant width 10.63 cm to

17.72 cm) and foliage shaded the mulched area. Consequently, the mulch effect decreased and there were no variations in abundance of thrips in different strata of squash grown on different mulch and no mulch treatments. Thus, no significant mulch effect was seen late season on abundance of T. palmi of all stages on squash.

In tomato, there were no significant interactions effect between mulch treatments and stratum although numerically mean number of thrips were less in reflective mulch treatments.

Statistical invariability might be due to very low number of thrips in every treatment. Cho et al.

(2000) found no difference in vertical distribution of adult melon thrips in field grown potato when population was very low.

Implications

Overall, we can conclude that middle stratum leaves of snap bean, jalapeno pepper and eggplant would be the preferred area to collect leaf samples to assess T. palmi population status of both adults and larvae. In the early and mid-season, sampling of middle stratum leaves of cucumber will provide information regarding population density of both adults and larvae.

However, at the end of the season, top and middle stratum leaves should be sampled to know the population status of adults and larvae, respectively. For squash, sampling of middle and top section leaves should provide population status of adults respectively in the early and late season.

However, bottom stratum leaves would be the best choice to know the population status of

larvae. Any time during the growing season, top and bottom strata leaves would be the best selection for sampling to determine the adult and larval population abundance, respectively on tomato plants.

This study results will increase the understanding of timing and occurrence of populations of melon thrips adults and larvae in the various plant strata on six commonly grown vegetable crops. Therefore, all these information from this study should provide essential guideline to the growers and farm managers to conduct timely, reliable and effective sampling programs ultimately in the implementation of a successful integrated pest management program.

Knowledge on the specific occurrence of melon thrips adults and larvae on the plant strata is very important in insecticide-based management program because control of insect pests through sufficient spray coverage is a crucial point. Partially, success of biological control-based management program depends on release of predator at the right place of the plants for their sustainability and augmentation. So, information from this study will be helpful in predator based biological control program. Moreover, metalized UV-reflective silver mulches reduced the melon thrips adults and larvae from all the stratum and crops used in this study. Therefore, silver reflective mulch could be an important cultural tool to manage melon thrips in field grown vegetable crops.

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Table 3-1. Leaf areas of six vegetable crops at three strata on different sampling dates. Crop Sampling date Leaf areas (Mean ± SE cm2) Top Middle Bottom Pepper 42DAP 11.34 ± 0.59* 36.44 ± 2.58 59.63 ± 2.27 54DAP 12.97 ± 1.12 34.82 ± 1.86 60.15 ± 2.48

Tomato 40DAP 25.34 ± 3.22 63.14 ± 7.62 74.10 ± 7.08 55DAP 31.43 ± 2.56 72.09 ± 5.71 73.20 ± 5.83

Bean 35DAP 46.67 ± 3.35 70.14 ± 4.08 62.96 ± 2.11 46DAP 46.41 ± 2.94 67.75 ± 3.98 62.42 ± 1.95

Cucumber 35DAP 123.28 ± 4.97 280.10 ± 18.33 290.65 ± 19.03 50DAP 122.10 ± 5.52 272.93 ± 17.45 285.78 ± 18.38

Squash 30DAP 218.25 ± 7.36 417.02 ± 32.42 276.80 ± 20.87 50DAP 215.28 ± 7.23 411.50 ± 27.25 300.42 ± 15.49

Eggplant 45DAP 187.02 ± 6.07 365.16 ± 21.30 378.02 ± 25.20 60DAP 190.10 ± 6.59 361.30 ± 21.7 375.55 ± 26.47 *Means represent sample size =10.

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Table 3-2. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area at three different strata of snap beans, cucumber and eggplant; mulch treatments were pooled. Sampling Stratum Thrips stage date Adult Larva Total Snap Beans 35 DAPy Top 1.12 ± 0.14az 2.92 ± 0.44c 4.04 ± 0.52b Middle 1.36 ± 0.24a 11.09 ± 2.19a 12.44 ± 2.37a Bottom 0.48 ± 0.11b 6.15 ± 1.30 b 6.61 ± 1.35b Statistics F; P 16.85; < 0.0001 26.54; < 0.0001 25.95; < 0.0001

46 DAP Top 3.10 ± 0.34a 7.39 ± 0.93c 10.49 ± 1.18b Middle 1.49 ± 0.22b 18.48 ± 2.48 a 19.97 ± 2.65a Bottom 0.77 ± 0.14c 15.31 ± 2.66b 16.08 ± 2.74b Statistics F; P 30.32; < 0.0001 23.85; < 0.0001 12.82; < 0.0001

Cucumber 35 DAP Top 6.12 ± 1.33a 2.90 ± 0.74b 9.19 ± 1.93b Middle 3.01 ± 0.36a 18.29 ± 4.01a 21.38 ± 4.22a Bottom 1.64 ± 0.48b 15.35 ± 3.18a 17.06 ± 3.31a Statistics F; P 28.19; < 0.0001 49.16; < 0.0001 20.88; < 0.0001

50 DAP Top 8.00 ± 0.89a 14.13 ± 2.63c 22.60 ± 2.68b Middle 4.42 ± 0.71b 31.71 ± 3.81a 34.93 ± 3.95a Bottom 1.39 ± 0.21c 15.77 ± 2.04b 17.16 ± 2.20c Statistics F; P 60.66; < 0.0001 29.69; < 0.0001 16.19; < 0.0001

Eggplant 45 DAP Top 1.94 ± 0.23a 3.55 ± 0.73b 5.49 ± 0.81b Middle 3.01 ± 0.52a 50.73 ± 8.57a 53.74 ± 8.86a Bottom 2.04 ± 0.26a 45.33 ± 6.52a 47.63 ± 6.79a Statistics F; P 1.39; 0.26 215.17; < 0.0001 184.11; < 0.0001

60 DAP Top 4.04 ± 0.38a 21.68 ± 1.97b 25.72 ± 2.05b Middle 3.40 ± 0.36ab 36.39 ± 2.19a 39.79 ± 2.34a Bottom 2.42 ± 0.30b 19.49 ± 2.05b 21.90 ± 2.11b Statistics F; P 6.60; 0.003 24.30; < 0.0001 23.53; < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yDAP (Days after planting)

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Table 3-3. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area at three different strata of Jalapeno pepper, squash and tomato; mulch treatments were pooled. Sampling date Stratum Thrips stage Adult Larva Total Jalapeno pepper 42 DAPy Top 0.42 ± 0.08az 3.12 ± 0.47a 3.55 ± 0.49a Middle 0.29 ± 0.06a 3.96 ± 0.78a 4.25 ± 0.82a Bottom 0.16 ± 0.05a 1.42 ± 0.35b 1.58 ± 0.38b Statistics F; P 2.58; 0.09 24.85; < 0.0001 30.16; < 0.0001

54 DAP Top 0.72 ± 0.19a 2.07 ± 0.36b 2.80 ± 0.49ab Middle 0.37 ± 0.06a 2.84 ± 0.57a 3.67 ± 0.64a Bottom 0.27 ± 0.06a 1.76 ± 0.32b 2.17 ± 0.39b Statistics F; P 0.75; 0.48 5.20; 0.01 6.94; 0.003

Squash 30 DAP Top 0.38 ± 0.07c 0.00 ± 0.00c 0.38 ± 0.07b Middle 3.59 ± 0.47a 0.21 ± 0.10b 2.52 ± 0.31a Bottom 0.61 ± 0.16b 2.02 ± 0.38a 3.96 ± 0.64a Statistics F; P 122.86; < 168.44; < .0001 133.72; < 0.0001 0.0001

50 DAP Top 13.24 ± 0.91a 2.97 ± 0.57c 16.21 ± 1.19b Middle 3.34 ± 0.48b 17.89 ± 3.15b 21.23 ± 3.10b Bottom 4.43 ± 0.79b 45.03 ± 4.02a 49.48 ± 4.41a Statistics F; P 59.27; < 0.0001 120.02; < 0.0001 32.65; < 0.0001

Tomato 40 DAP Top 0.53 ± 0.07a 0.06 ± 0.02a 0.59 ± 0.07a Middle 0.27 ± 0.04a 0.08 ± 0.03a 0.35 ± 0.05ab Bottom 0.08 ± 0.02b 0.12 ± 0.04a 0.19 ± 0.04b Statistics F; P 17.26; < 0.0001 1.57; 0.22 7.91; 0.001

55 DAP Top 0.50 ± 0.09a 0.34 ± 0.20b 0.84 ± 0.26a Middle 0.10 ± 0.02b 0.29 ± 0.07ab 0.39 ± 0.08a Bottom 0.20 ± 0.03b 0.42 ± 0.12a 0.62 ± 0.13a Statistics F; P 13.61; < 0.0001 3.75; 0.03 2.39; 0.10 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yDAP (Days after planting).

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Table 3-4. Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of snap beans on 35 DAP and 46 DAP. Sampling Thrips stage date Mulchy Adult Larva Total Top Middle Bottom Top Middle Bottom Top Middle Bottom 35 DAPx NM 2.7 ± 0.7abcz 4.6 ± 0.8a 0.9 ± 0.2ab 6.7 ± 2.2a 44.2 ± 14.6ab 26.9 ± 13.1a 9.3 ± 1.9a 48.7 ± 14.6ab 27.8 ± 12.9a WB 2.7 ± 0.6abc 8.6 ± 1.8a 3.0 ± 0.6a 8.7 ± 2.7a 72.2 ± 17.7a 28.1 ± 7.1a 11.4 ± 3.1a 80.7 ± 19.0a 31.1 ± 7.5a BB 3.1 ± 0.5a 3.9 ± 0.9ab 1.4 ± 1.0ab 5.7 ± 1.2a 25.6 ± 8.1b 17.5 ± 5.9a 8.8 ± 1.7a 29.6 ± 7.7b 18.9 ± 6.5a BW 2.8 ± 0.3ab 4.5 ± 1.0a 1.4 ± 0.5ab 6.9 ± 1.3a 36.3 ± 4.1ab 15.3 ± 4.4a 9.7 ± 1.5a 40.7 ± 3.7a 16.7 ± 4.8a SW 0.8 ± 0.3c 0.9 ± 0.4bc 0.3 ± 0.1b 3.6 ± 1.9ab 5.4 ± 0.6c 1.7 ± 0.6b 4.3 ± 1.8ab 6.2 ± 1.0c 2.0 ± 0.6b SB 0.7 ± 0.3bc 0.6 ± 0.2c 0.3 ± 0.1b 1.3 ± 0.2b 3.0 ± 0.7c 3.2 ± 0.8b 1.9 ± 0.4b 3.6 ± 0.7c 3.5 ± 0.7b Statistics F; P 4.68; 8.01; 4.81; 5.01; 18.98; 14.86; 6.89; 24.92; 19.13, 0.001 < 0.0001 0.001 0.001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001

46 DAP NM 5.4 ± 0.8a 4.6 ± 0.8ab 2.2 ± 0.7ab 16.9 ± 3.8a 49.2 ± 4.2abc 30.7 ± 5.8a 22.3 ± 3.5ab 53.8 ± 4.7ab 32.9 ± 6.4a WB 8.7 ± 0.4a 7.4 ± 1.9a 3.9 ± 0.1a 19.7 ± 2.7a 105.8 ± 14.5a 92.3 ± 16.0a 28.3 ± 2.7a 113.1 ± 16.2a 96.1 ± 16.7a BB 5.6 ± 1.8a 4.3 ± 0.6ab 1.5 ± 0.2abc 16.8 ± 2.2a 64.1 ± 7.2ab 47.5 ± 8.4a 22.4 ± 4.0ab 68.4 ± 7.2ab 49.0 ± 8.4a BW 8.9 ± 1.2a 2.9 ± 0.6ab 1.9 ± 0.3abc 19.4 ± 4.9a 31.3 ± 4.9bc 41.0 ± 6.8a 28.2 ± 5.6ab 34.2 ± 4.6bc 42.8 ± 6.8a SW 3.2 ± 1.4a 1.4 ± 0.6b 1.7 ± 1.4bc 3.7 ± 1.1b 18.0 ± 5.7c 8.6 ± 4.0b 6.9 ± 2.3c 19.4 ± 5.8c 10.2 ± 4.7b SB 2.8 ± 0.3a 3.8 ± 2.1ab 0.6 ± 0.3c 6.0 ± 1.4ab 32.2 ± 9.0bc 9.6 ± 3.7b 8.8 ± 1.6bc 36.0 ± 10.0bc 10.1 ± 3.9b Statistics F; P 2.28; 2.84; 4.70; 5.92; 6.03; 14.68; 5.56; 6.28; 15.18; 0.06 0.02 0.001 0.0003 0.0002 < 0.0001 0.0005 0.0002 < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). xDays after planting (DAP).

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Table 3-5. Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of cucumber on 35 DAP and 50 DAP. Sampling Thrips stage date Mulchy Adult Larva Total Top Middle Bottom Top Middle Bottom Top Middle Bottom 35 DAPx NM 44.2 ± 7.5abz 54.2 ± 11.3a 22.5 ± 7.3ab 27.2 ± 11.7a 285.0 ± 64.5ab 371.7 ± 65.5a 72.2 ± 17.8a 340.0 ± 58.3ab 395.0 ± 58.5a WB 78.7 ± 24.7a 50.8 ± 9.6a 58.3 ± 25.9a 30.1 ± 14.7a 567.5 ± 86.0a 318.3 ± 139.8a 109.6 ± 35.4a 619.2 ± 80.9a 377.5 ± 132.6a BB 25.5 ± 5.6abc 37.5 ± 6.4a 9.8 ± 3.7bc 13.0 ± 1.6a 263.3 ± 66.5ab 225.5 ± 22.0a 39.3 ± 6.6ab 301.7 ± 71.4ab 233.2 ± 21.0a BB 13.1 ± 4.0bc 27.6 ± 3.7a 13.3 ± 3.6abc 11.9 ± 4.1ab 95.0 ± 18.7b 129.2 ± 18.0a 25.8 ± 6.9bc 123.4 ± 20.3b 143.3 ± 19.5a SW 8.6 ± 3.9c 15.4 ± 4.0b 3.2 ± 0.4c 2.3 ± 0.8b 11.3 ± 8.6c 10.1 ± 2.4b 11.75 ± 3.5c 27.6 ± 10.5c 14.1 ± 2.5b SB 11.0 ± 4.5c 17.0 ± 3.5b 6.9 ± 1.3bc 1.4 ± 0.4b 7.7 ± 2.8c 18.8 ± 6.9b 13.3 ± 4.3c 25.5 ± 4.68c 26.6 ± 6.1b Statistics F; P 8.44; 3.08; 6.87; 8.51; 23.36; 17.92; 11.93; 30.15; 29.95; < 0.0001 0.02 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 50 DAP NM 56.7 ± 7.8a 55.4 ± 12.5a 25.8 ± 5.5a 59.2 ± 5.0ab 458.3 ± 62.1a 291.7 ± 63.4a 115.8 ± 11.9ab 513.8 ± 73.0ab 317.5 ± 66.1a WB 30.0 ± 2.4a 34.2 ± 5.0a 21.7 ± 9.7ab 185.0 ± 15.2a 545.2 ± 67.2a 262.5 ± 83.9a 223.3 ± 16.8a 579.3 ± 66.4a 284.2 ± 93.0ab BB 59.2 ± 8.3a 55.5 ± 12.2a 15.8 ± 3.2ab 80.0 ± 21.4ab 349.2 ± 31.2ab 174.2 ± 23.0a 139.2 ± 22.2ab 404.7 ± 36.8abc 190.0 ± 20.1ab BW 38.3 ± 12.2a 21.3 ± 6.9a 18.3 ± 5.2ab 54.2 ± 10.1b 175.0 ± 28.1ab 145.8 ± 34.4a 92.5 ± 19.1ab 196.3 ± 33.9bc 164.2 ± 38.3ab SW 21.6 ± 6.1a 22.1 ± 8.4a 6.7 ± 1.4b 42.0 ± 17.5b 395.8 ± 164.0ab 116.7 ± 26.8a 63.6 ± 18.1b 417.9 ± 161.8abc 123.3 ± 28.1ab SB 25.6 ± 11.8a 22.5 ± 5.0a 7.1 ± 2.4b 65.5 ± 28.6ab 153.8 ± 47.9b 90.8 ± 24.4b 94.1 ± 39.5b 175.8 ± 47.6c 97.9 ± 23.4b Statistics F; P 2.38; 0.06 2.68; 0.31 3.29; 0.01 4.55; 0.002 3.85; 0.005 2.49; 0.04 3.85; 0.005 4.45, 0.002 3.17; 0.01 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). xDays after planting (DAP).

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Table 3-6. Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of eggplant on 45 DAP and 60 DAP. Sampling Thrips stage date 45 DAPx Mulchy Adult Larva Total Top Middle Bottom Top Middle Bottom Top Middle Bottom NM 11.8 ± 1.3az 42.1 ± 5.8ab 21.7 ± 3.2b 35.9 ± 22.8abc 744.8 ± 162.7a 721.7 ± 125.8ab 47.7 ± 22.1ab 786.9 ± 163.0a 743.3±127.7ab WB 22.2 ± 7.0a 95.8 ± 17.4a 49.2 ± 11.8a 15.2 ± 4.2abc 1580.8 ± 305.2a 1317.5 ± 319.5a 37.3 ± 10.8ab 1676.7 ± 298.4a 1366.7 ± 327.8a BB 19.6 ± 4.1a 38.3 ± 6.2abc 27.5 ± 2.9b 34.0 ± 9.2ab 1266.7 ± 139.0a 935.0 ± 253.9ab 53.6 ± 11.5ab 1305.0 ± 135.6a 962.5 ± 256.6a BW 15.8 ± 3.7a 59.2 ± 25.4ab 46.7 ± 9.8a 50.5 ± 15.3a 557.50 ± 74.9a 602.50 ± 94.3ab 66.3 ± 18.5a 616.7 ± 99.8a 649.2 ± 88.1ab SW 8.3 ± 0.5a 10.8 ± 1.1c 22.5 ± 9.9b 11.8 ± 3.7bc 118.3 ± 38.9b 287.5 ± 75.3b 20.1 ± 3.6ab 129.2 ± 39.9b 310.0 ± 77.7b SB 9.6 ±1.2a 17.5 ± 4.8bc 17.5 ± 5.5b 12.1 ± 8.0c 177.5 ± 41.0b 279.2 ± 50.7b 21.7 ± 7.6b 195.0 ± 39.9b 296.7 ± 54.9b Statistics F; P 1.27; 0.29 7.07; < 0.0001 2.65; 0.03 4.63; 0.002 14.07; < 0.0001 4.73; 0.002 3.24; 0.01 18.42; < 0.0001 6.23; 0.0002

60 DAP NM 35.8 ± 5.8a 70.0 ± 15.2a 60.8 ± 13.8a 189.2 ± 41.1a 470.8 ± 74.7a 449.2 ± 142.3a 225.0 ± 45.6a 540.8 ± 88.5a 510.0 ± 137.7a WB 29.2 ± 2.1a 57.5 ± 13.2a 34.2 ± 4.2ab 165.0 ± 41.5a 747.5 ± 82.8a 323.3 ± 42.3a 194.2 ± 41.5a 805.0 ± 94.9a 357.5 ± 39.1a BB 31.7 ± 8.2a 38.3 ± 7.5a 42.5 ± 7.7a 149.2 ± 18.4a 452.5 ± 31.2a 237.5 ± 46.1a 180.8 ± 24.2a 490.8 ± 36.5a 280.0 ± 52.2a BW 35.8 ± 13.5a 56.7 ± 8.9a 38.3 ± 10.1ab 100.8 ± 12.5a 434.2 ± 47.3a 235.0 ± 37.5a 136.7 ± 25.6a 490.8 ± 45.9a 273.3 ± 30.2a SW 24.2 ± 4.4a 35.0 ± 8.0a 12.5 ± 2.5b 156.7 ± 17.9a 542.5 ± 86.4a 265.0 ± 75.7a 180.8 ± 16.9a 577.5 ± 92.2a 277.5 ± 77.2a SB 27.5 ± 6.3a 37.5 ± 17.1a 29.2 ± 12.6ab 228.3 ± 55.2a 507.5 ± 25.7a 244.2 ± 25.0a 255.8 ± 55.3a 545.0 ± 24.6a 273.3 ± 28.9a Statistics F; P 0.25; 0.94 1.78; 0.13 3.56; 0.007 1.91; 0.11 1.22; 0.31 1.54; 0.19 1.53; 0.19 1.20; 0.32 2.02; 0.09 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). xDays after planting (DAP).

106

Table 3-7. Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of Jalapeno pepper on 42 DAP and 54 DAP. Sampling Thrips stage date Mulchy Adult Larva Total Top Middle Bottom Top Middle Bottom Top Middle Bottom 42 DAPx NM 0.3 ± 0.1az 0.5 ± 0.5a 0.4 ± 0.2ab 1.9± 0.7a 8.5 ± 4.5a 4.6 ± 2.8ab 2.2 ± 0.6a 9.0 ± 4.9a 4.9 ± 3.0ab WB 0.3 ± 0.1a 0.7 ± 0.2a 1.0 ± 0.4a 1.1 ± 0.2a 8.7 ± 3.3a 8.4 ± 2.9a 1.4 ± 0.2a 9.4 ± 3.5a 9.5 ± 2.9a BB 0.2 ± 0.1a 0.5 ± 0.1a 0.3 ± 0.1ab 2.1 ± 0.5a 6.5 ± 2.0a 2.7 ± 0.6ab 2.2 ± 0.6a 7.0 ± 2.0a 3.0 ± 0.7ab BW 0.3 ± 0.2a 0.5 ± 0.1a 0.4 ± 0.2ab 2.3 ± 0.5a 6.9 ± 2.6a 3.3 ± 1.1ab 2.5 ± 0.5a 7.4 ± 2.7a 3.6 ± 1.1ab SW 0.1 ± 0.1a 0.1 ± 0.1a 0.1 ± 0.1b 0.5 ± 0.1a 1.6 ± 0.7a 0.3 ± 0.1c 0.6 ± 0.3a 1.6 ± 0.7a 0.4 ± 0.2c SB 0.1 ± 0.15a 0.5 ± 0.1a 0.2 ± 0.1ab 0.8 ± 0.4a 2.5 ± 0.8a 1.2 ± 0.6bc 0.8 ± 0.1a 3.0 ± 0.7a 1.4 ± 0.6bc Statistics F; P 1.61; 0.18 2.37; 0.07 2.86; 0.02 1.48; 0.22 2.30; 0.06 6.27; 0.0002 1.58; 0.189 2.27; 0.06 7.02; 0.0001

54 DAP NM 0.3 ± 0.1a 0.5 ± 0.2a 0.4 ± 0.2ab 1.8 ± 0.7a 2.5 ± 0.7a 2.1 ± 1.0b 2.1 ± 0.8a 3.0 ± 0.8ab 2.5 ± 1.1bc WB 0.6 ± 0.3a 0.8 ± 0.3a 1.7 ± 0.4a 1.2 ± 0.2a 9.2 ± 3.3a 9.8 ± 2.0a 1.8 ± 0.3a 10.0 ± 3.6a 11.4 ± 2.4a BB 0.3 ± 0.1a 0.7 ± 0.3a 0.9 ± 0.1ab 1.2 ± 0.4a 5.3 ± 1.6a 4.6 ± 1.6ab 1.5 ± 0.4a 6.0 ± 1.8ab 5.5 ± 1.6abc BW 0.9 ± 0.4a 0.5 ± 0.1a 0.7 ± 0.2ab 1.6 ± 0.5a 2.8 ± 1.1a 5.5 ± 1.0ab 2.5 ± 0.9a 3.3 ± 1.2ab 6.2 ± 0.8ab SW 0.2 ± 0.1a 0.5 ± 0.2a 0.1 ± 0.1b 0.6± 0.4ab 2.0 ± 0.4a 1.0 ± 0.2b 0.8 ± 0.3ab 2.5 ± 0.3ab 1.1 ± 0.3c SB 0.1 ± 0.1a 0.2 ± 0.1a 0.2 ± 0.1ab 0.2 ± 0.1b 2.1 ± 0.7a 2.5 ± 1.6b 0.3 ± 0.1b 2.3 ± 0.8b 2.7 ± 1.7bc Statistics F; P 1.20; 0.32 0.76; 0.59 3.75; 0.006 4.38; 0.003 2.27; 0.07 4.93; 0.001 4.26; 0.003 2.60; 0.04 6.45; 0.0002 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). xDays after planting (DAP).

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Table 3-8. Mean ± SE number of melon thrips (T. palmi) per one leaf at different strata of squash on 30 DAP and 50 DAP. Sampling Thrips stage date Mulchy Adult Larva Total Top Middle Bottom Top Middle Bottom Top Middle Bottom 30 DAPx NM 4.2 ± 1.8abz 24.5 ± 5.1a 15.1 ± 5.8a 0.0 ± 0.0a 7.4 ± 6.4a 28.1 ± 3.2ab 4.2 ± 1.8a 31.9 ± 4.6a 43.2 ± 7.3a WB 5.0 ± 2.2a 63.8 ± 20.0a 23.2 ± 13.4a 0.0 ± 0.0a 1.8 ± 1.4a 71.1 ± 28.8a 5.0 ± 2.2ab 65.7 ± 20.0a 94.3 ± 25.4a BB 5.2 ± 0.8a 49.3 ± 7.5a 8.8 ± 2.9a 0.0 ± 0.0a 1.7 ± 0.9a 45.7 ± 8.7a 5.2 ± 0.8a 50.9 ± 7.9a 54.5 ± 8.5a BW 1.7 ± 0.2ab 33.5 ± 10.4a 6.1 ± 0.2a 0.0 ± 0.0a 1.9 ± 0.8a 30.9 ± 9.5ab 1.7 ± 0.2ab 35.4 ± 10.7a 37.0 ± 9.4ab SW 2.3 ± 0.7ab 50.5 ± 10.8a 5.4 ± 1.8a 0.0 ± 0.0a 0.4 ± 0.3a 20.6 ± 3.1ab 2.3 ± 0.7ab 50.9 ± 10.8a 26.0 ± 1.7ab SB 1.4 ± 0.1b 17.0 ± 1.2a 2.7 ± 1.0a 0.0 ± 0.0a 0.7 ± 0.7a 5.6 ± 2.1b 1.4 ± 1.0b 17.7 ± 1.6a 8.3 ± 2.5b Statistics F; P 2.96; 0.02 1.28; 0.29 2.23; 0.07 0.0, 1.00 1.77; 0.14 2.89; 0.02 3.33; 0.01 1.22; 0.32 4.88; 0.001

50 DAP NM 102.5 ± 10.3a 66.7 ± 19.8ab 37.5 ± 8.3a 20.8 ± 4.6a 142.5 ± 49.3a 630.0 ± 128.8a 123.3 ± 12.7a 209.2 ± 65.8a 667.5 ± 129.0a WB 123.3 ± 2.0a 27.5 ± 17.0b 72.5 ± 25.6a 37.5 ± 8.54a 442.5 ± 162.6a 505.0 ± 117.7a 160.8 ± 13.1a 470.0 ± 152.9a 577.5 ± 109.7a BB 153.3 ± 32.2a 82.5 ± 24.2a 80.0 ± 42.7a 50.8 ± 24.0a 368.3 ± 156.6a 631.7 ± 138.4a 204.2 ± 42.7a 450.8 ± 165.1a 711.7 ± 173.2a BW 104.2 ± 11.0a 51.7 ± 15.6ab 40.0 ± 9.3a 12.5 ± 2.9a 199.2 ± 48.1a 455.0 ± 65.3a 116.7± 9.6a 250.8 ± 60.2a 495.0 ± 61.6a SW 107.5 ± 15.0a 32.5 ± 10.3ab 33.3 ± 4.9a 14.2 ± 5.5a 385.8 ± 175.6a 525.0 ± 91.7a 121.7 ± 14.4a 418.3 ± 169.4a 558.3 ± 89.0a SB 93.3 ± 12.3a 69.3 ± 21.3a 55.8 ± 28.5a 17.5 ± 1.6a 228.3 ± 114.5a 501.7 ± 190.8a 110.8 ± 13.1a 297.6 ± 107.6a 557.5 ± 218.9a Statistics F; P 0.22; 0.95 3.21; 0.01 0.51; 0.76 2.26; 0.06 1.59; 0.18 0.20; 0.96 0.67; 0.65 1.40; 0.24 0.26, 0.93 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). xDays after planting (DAP).

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Table 3-9. Mean ± SE number of melon thrips (T. palmi) per one leaf at different stratum of tomato on 40 DAP and 55 DAP. Sampling Thrips stage date Mulchy Adult Larva Total Top Middle Bottom Top Middle Bottom Top Middle Bottom 40 DAPx NM 0.5 ± 0.2az 0.5 ± 0.3a 0.1 ± 0.1a 0.1 ± 0.1a 0.3 ± 0.1a 0.1 ± 0.1ab 0.6 ± 0.3a 0.8 ± 0.4a 0.2 ± 0.1ab WB 0.8 ± 0.1a 1.0 ± 0.4a 0.5 ± 0.2a 0.1 ± 0.1a 0.4 ± 0.3a 0.9 ± 0.5a 0.9 ± 0.1a 1.4 ± 0.5a 1.4 ± 0.5a BB 0.6 ± 0.3a 0.7 ± 0.1a 0.3 ± 0.1a 0.0 ± 0.0a 0.3 ± 0.2a 0.7 ± 0.4ab 0.6 ± 0.3a 1.0 ± 0.3a 1.0 ± 0.4ab BW 0.6 ± 0.2a 1.0 ± 0.3a 0.3 ± 0.2a 0.2 ± 0.1a 0.2 ± 0.2a 0.3 ± 0.1ab 0.7 ± 0.1a 1.1 ± 0.4a 0.6 ± 0.2ab SW 0.3 ± 0.1a 0.6 ± 0.1a 0.2 ± 0.0a 0.1 ± 0.1a 0.1 ± 0.1a 0.1 ± 0.7ab 0.4 ± 0.1a 0.6 ± 0.1a 0.3 ± 0.1ab SB 0.6 ± 0.2a 0.4 ± 0.1a 0.1 ± 0.1a 0.0 ± 0.0a 0.1 ± 0.1a 0.0 ± 0.0b 0.6 ± 0.2a 0.4 ± 0.1a 0.1 ± 0.1b Statistics F; P 0.71; 0.62 0.56; 0.73 0.99; 0.43 0.64; 0.67 0.89; 0.49 2.60; 0.04 0.87; 0.50 0.66; 0.65 3.45; 0.01

55 DAP NM 0.6 ± 0.2a 0.3 ± 0.1a 0.8 ± 0.3a 0.2 ± 0.1a 0.6 ± 0.3a 2.3 ± 1.5a 0.7 ± 0.5a 0.8 ± 0.4a 3.1 ± 1.7a WB 1.2 ± 0.3a 0.3 ± 0.2a 0.9 ± 0.4a 0.2 ± 0.1a 1.6 ± 0.9a 1.5 ± 0.3a 1.3 ± 0.3a 1.9 ± 1.0a 2.3 ± 0.6a BB 0.7 ± 0.3a 0.5 ± 0.1a 0.5 ± 0.1a 0.3 ± 0.3a 0.5 ± 0.1a 1.9 ± 1.5a 1.0 ± 0.4a 0.9 ± 0.1a 2.4 ± 1.5a BW 0.8 ± 0.4a 0.3 ± 0.2a 0.7 ± 0.3a 1.6 ± 1.5a 1.4 ± 0.8a 0.5 ± 0.1a 2.3 ± 1.9a 1.7 ± 0.2a 1.2 ± 0.4a SW 0.2 ± 0.0a 0.3 ± 0.1a 0.3 ± 0.1a 0.2 ± 0.1a 0.5 ± 0.2a 0.9 ± 0.3a 0.4 ± 0.1a 0.8 ± 0.4a 1.2 ± 0.3a SB 0.5 ± 0.2a 0.2 ± 0.1a 0.4 ± 0.1a 0.3 ± 0.3a 0.5 ± 0.2a 0.0 ± 0.2a 0.7 ± 0.5a 0.7 ± 0.2a 0.7 ± 0.3a Statistics F; P 1.03; 0.41 0.62; 0.69 0.27; 0.93 0.32; 0.90 0.79; 0.56 1.57; 0.18 0.86; 0.51 0.87; 0.51 1.08; 0.38 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). xDays after planting (DAP).

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Table 3-10. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of snap beans and cucumber grown on different plastic mulches and a no-mulch; strata were pooled. Sampling Mulch Thrips stage date Adult Larva Total Snap Beans 35 DAPx No mulch 1.13 ± 0.22az 10.04 ± 2.72a 11.13 ± 2.69a White on black 1.89 ± 0.34a 13.85 ± 3.40a 15.73 ± 3.68a Black on black 1.19 ± 0.22a 6.39 ± 1.37a 7.58 ± 1.37a Black on white 1.21 ± 0.19a 7.56 ± 1.38a 8.76 ± 1.44a Silver on white 0.28 ± 0.07b 1.49 ± 0.37b 1.76 ± 0.39b Silver on black 0.23 ± 0.05b 0.99 ± 0.14b 1.22 ± 0.14b Statistics F; P 16.27; < 0.0001 23.90; < 0.0001 29.33; < 0.0001

46 DAP No mulch 1.83 ± 0.30ab 13.17 ± 1.54a 15.00 ± 1.51a White on black 2.97 ± 0.46a 28.84 ± 4.66a 31.81 ± 4.49a Black on black 1.73 ± 0.42ab 17.23 ± 2.28a 18.96 ± 2.18a Black on white 2.19 ± 0.59ab 12.79 ± 1.49a 14.97 ± 1.44a Silver on white 0.96 ± 0.33c 4.02 ± 1.01b 4.98 ± 1.05b Silver on black 1.04 ± 0.30bc 6.30 ± 1.63b 7.34 ± 1.77b Statistics F; P 8.58; 0.0003 14.95; < 0.0001 14.82; < 0.0001

Cucumber 35 DAP No mulch 5.24 ± 1.05ab 20.97 ± 4.23a 26.32 ± 3.51a White on black 8.50 ± 2.31a 28.04 ± 7.03a 36.65 ± 6.21a Black on black 3.12 ± 0.67bc 15.09 ± 3.30ab 18.32 ± 3.12ab Black on white 2.09 ± 0.35bcd 7.34 ± 1.32b 9.53 ± 1.26b Silver on white 1.13 ± 0.32d 0.78 ± 0.26c 2.02 ± 0.40c Silver on black 1.45 ± 0.36cd 0.86 ± 0.26c 2.42 ± 0.33c Statistics F; P 15; < 0.0001 40.69; < 0.0001 34.67; < 0.0001

50 DAP No mulch 6.32 ± 1.33ab 26.54 ± 4.40ab 32.86 ± 4.13ab White on black 3.72 ± 0.63abc 36.94 ± 4.50a 40.66 ± 4.80a Black on black 7.83 ± 1.62a 16.29 ± 3.89c 27.40 ± 3.10ab Black on white 3.80 ± 1.17bc 13.30 ± 1.48bc 17.10 ± 1.10bc Silver on white 2.34 ± 0.65c 18.36 ± 6.07bc 20.70 ± 5.99bc Silver on black 3.61 ± 1.06c 11.80 ± 2.44c 14.65 ± 3.15c Statistics F; P 7.80; < 0.0001 7.96; 0.0004 7.13; 0.0008 zMeans within the same column followed by same letters were not significantly different at P ≤ 0.05 according to Tukey’s HSD test xDays after planting (DAP).

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Table 3-11. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of eggplant and jalapeno pepper grown on different plastic mulches and a no-mulch; strata were pooled. Sampling date Mulch Thrips stage Adult Larva Total Eggplant 45 DAPx No mulch 1.96 ± 0.25abcz 34.51 ± 7.66a 36.47 ± 7.75a White on black 4.26 ± 0.71a 65.12 ± 16.36a 70.06 ± 16.80a Black on black 2.35 ± 0.24ab 51.03 ± 11.90a 53.39 ± 11.89a Black on white 3.08 ± 0.63a 28.26 ± 5.23a 31.34 ± 5.56a Silver on white 1.11 ± 0.22c 9.57 ± 2.76b 10.68 ± 2.84b Silver on black 1.21 ± 0.16bc 10.74 ± 2.50b 11.80 ± 2.46b Statistics F; P 9.13; 0.0002 13.20; < 0.0001 15.97; < 0.0001

60 DAP No mulch 4.54 ± 0.49a 29.13 ± 3.77ab 33.67 ± 3.91a White on black 3.36 ± 0.38ab 31.66 ± 4.97a 35.02 ± 5.17a Black on black 3.22 ± 0.44ab 22.25 ± 2.40ab 25.47 ± 2.51a Black on white 3.73 ± 0.66ab 19.66 ± 2.60b 23.39 ± 2.72a Silver on white 2.14 ± 0.38b 25.27 ± 3.61ab 27.41 ± 3.76a Silver on black 2.72 ± 0.54b 27.14 ± 3.33ab 29.86 ± 3.44a F; P 3.76; 0.005 2.51; 0.04 2.38; 0.06

Jalapeno pepper 42 DAP No mulch 0.37 ± 0.12ab 3.94 ± 1.20ab 4.31 ± 1.27a White on black 0.52 ± 0.08a 3.97 ± 0.91a 4.50 ± 0.92a Black on black 0.27 ± 0.07ab 3.35 ± 0.73a 3.62 ± 0.77a Black on white 0.34 ± 0.12ab 3.69 ± 0.82a 4.02 ± 0.86a Silver on white 0.09 ± 0.05b 0.76 ± 0.20b 0.86 ± 0.22b Silver on black 0.16 ± 0.05ab 1.29 ± 0.34ab 1.45 ± 0.34ab Statistics F; P 3.22; 0.04 4.31; 0.009 4.57; 0.007

54 DAP No mulch 0.35 ± 0.11a 2.01 ± 0.53ab 2.36 ± 0.63ab White on black 0.77 ± 0.18a 4.32 ± 0.94a 5.10 ± 0.98a Black on black 0.45 ± 0.09a 2.67 ± 0.52ab 3.12 ± 0.57ab Black on white 0.80 ± 0.33a 2.42 ± 0.41ab 3.21 ± 0.68ab Silver on white 0.22 ± 0.08b 1.00 ± 0.26b 1.21 ± 0.25b Silver on black 0.14 ± 0.04b 0.93 ± 0.30b 2.15 ± 0.76b Statistics F; P 59.27, < 0.0001 120.02, < 0.0001 32.65, < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. xDays after planting (DAP).

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Table 3-12. Mean ± SE number of melon thrips (T. palmi) per 25 cm2 leaf area of squash and tomato grown on different plastic mulches and a no-mulch; strata were pooled. Sampling Mulch Thrips stage date Adult Larva Total Squash 30 DAP No mulch 1.20 ± 0.29abz 0.78 ± 0.28a 2.10 ± 0.48a White on black 2.58 ± 0.91a 1.48 ± 0.79a 4.34 ± 1.26a Black on black 1.86 ± 0.59ab 0.96 ± 0.41a 2.86 ± 0.60a Black on white 1.19 ± 0.48ab 0.68 ± 0.31a 1.89 ± 0.51ab Silver on white 1.72 ± 0.68b 0.42 ± 0.18a 1.89 ± 0.41ab Silver on black 0.62 ± 0.20b 0.13 ± 0.06a 0.66 ± 0.14b Statistics F; P 3.07; 0.04 2.58; 0.07 6.15; 0.003

50 DAP No mulch 6.36 ± 1.31a 21.17 ± 7.50a 27.53 ± 6.92a White on black 7.34 ± 1.87a 24.42 ± 6.28a 31.76 ± 5.40a Black on black 9.83 ± 2.36a 26.95 ± 7.41a 36.77 ± 7.31a Black on white 6.19 ± 1.37a 17.14 ± 4.97a 23.33 ± 4.28a Silver on white 5.74 ± 1.55a 22.93 ± 6.52a 28.67 ± 5.59a Silver on black 6.56 ± 1.30a 19.22 ± 7.25a 25.78 ± 7.35a Statistics F; P 0.83; 0.54 1.95; 0.10 1.43; 0.23

Tomato 40 DAP No mulch 0.24 ± 0.092a 0.08 ± 0.03a 0.33 ± 0.11a White on black 0.45 ± 0.10a 0.16 ± 0.07a 0.61 ± 0.09a Black on black 0.30 ± 0.10a 0.12 ± 0.06a 0.42 ± 0.10a Black on white 0.34 ± 0.09a 0.10 ± 0.04a 0.44 ± 0.09a Silver on white 0.19 ± 0.04a 0.03 ± 0.02a 0.23 ± 0.05a Silver on black 0.24 ± 0.08a 0.007 ± 0.007a 0.25 ± 0.08a Statistics F; P 0.93; 0.49 2.02; 0.09 2.15; 0.11

55 DAP No mulch 0.27 ± 0.06a 0.37 ± 0.18a 0.63 ± 0.20a White on black 0.44 ± 0.13a 0.38 ± 0.11a 0.82 ± 0.15a Black on black 0.30 ± 0.09a 0.35 ± 0.18a 0.64 ± 0.19a Black on white 0.31 ± 0.13a 0.62 ± 0.39a 0.94 ± 0.50a Silver on white 0.13 ± 0.02a 0.19 ± 0.05a 0.32 ± 0.05a Silver on black 0.18 ± 0.07a 0.16 ± 0.07a 0.34 ± 0.12a F; P 1.55; 0.19 0.74; 0.60 1.82; 0.12 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. xDays after planting (DAP).

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Table 3-13. Percent concentration (ppm) of Nitrogen (N), Phosphorus (P) and Potassium (K) in different stratum leaves of six vegetable crops grown on different mulches. Mulchy N P K Top Middle Bottom Top Middle Bottom Top Middle Bottom Eggplant SB 1.38z 2.31 2.69 0.25 0.22 0.22 1.90 1.06 1.83 SW 4.04 2.81 1.91 0.24 0.22 0.19 1.61 1.04 1.61 WB 1.32 1.90 1.37 0.29 0.27 0.14 2.19 0.78 1.97 NM 2.60 3.21 2.93 0.24 0.25 0.15 2.31 2.18 1.91 BB 3.42 2.75 3.52 0.34 0.26 0.25 1.66 2.49 1.82 BW 3.02 3.65 3.87 0.28 0.27 0.22 1.83 2.16 2.42

Squash SB 4.96 5.22 4.79 0.18 0.18 0.21 0.75 0.92 1.37 WB 4.40 4.03 3.94 0.21 0.20 0.23 1.28 1.02 1.10

Cucumber SB 3.34 3.34 3.18 0.26 0.36 0.35 1.98 1.50 0.40 WB 3.65 3.12 4.66 0.27 0.36 0.48 0.31 1.27 1.13

Snap Beans SB 4.75 4.75 4.51 0.34 0.37 0.31 0.75 2.17 1.77 WB 4.17 3.78 3.63 0.28 0.26 0.26 2.47 2.14 2.50

Pepper SB 4.89 4.52 4.05 0.41 0.36 0.33 1.20 0.86 1.05 WB 2.99 4.50 4.70 0.28 0.31 0.36 0.63 0.67 0.90

Tomato SB 3.71 3.63 3.76 0.18 0.18 0.25 1.00 1.34 1.17 WB 3.92 3.92 4.89 0.30 0.30 0.31 0.69 1.02 0.81 yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). zoncentration assessed in ppm.

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Table 3-14. Percent concentration (ppm) of Boron (B), Zinc (Zn), Copper (Cu), Iron (Fe) and Manganese (Mn) in different stratum leaves of six vegetable crops grown on different mulches. Mulchy B Zn Cu Fe Mn Eggplant T* M** B*** T M B T M B T M B T M B SB 146z 131 134 21 16 17 13.7 10.8 10.1 209 234 226 66 83 110 SW 106 126 151 20 16 17 13.2 10.6 10.7 156 176 206 66 103 140 WB 132 120 91 19 14 14 13.4 10.1 9.9 247 209 151 72 97 108 NM 129 126 120 21 16 17 11.7 9.7 11.6 220 233 191 74 93 105 BB 129 141 147 24 18 17 14.9 14.3 13.3 195 136 154 62 94 103 BW 141 141 156 19 16 14 12.5 11.9 11.4 231 156 169 63 91 104

Squash SB 112 117 119 14 23 19 16.9 10.9 7.5 160 197 200 251 92 100 WB 138 123 122 15 23 19 9.2 8.5 8.8 118 121 110 123 62 82

Cucumber SB 225 296 164 45 42 27 16.1 14.7 9.7 113 120 267 162 56 78 WB 161 165 168 21 46 30 8.5 16.7 11.2 245 238 160 192 59 65

Snap Beans SB 110 151 131 30 35 38 11.7 13.6 12.8 131 163 112 228 102 114 WB 132 137 188 41 35 38 14.1 11.7 12.4 105 180 117 162 71 97

Pepper SB 119 93 130 22 18 11 10.1 14.5 11.9 235 189 205 161 133 205 WB 114 116 144 10 19 12 14.8 12.2 12.1 175 142 129 304 123 230

Tomato SB 129 132 140 14 29 37 8.2 13.7 8.2 107 165 154 97 95 140 WB 167 131 95 26 29 31 16.3 11.1 13.3 112 329 139 248 77 181 yNM (No-mulch), WB (White on black), BB (Black on black), BW (Black on white), SW (Silver on white), and SB (Silver on black). zconcentration assessed in ppm. *Top, **Middle, ***Bottom

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CHAPTER 4 GROWTH AND YIELD RESPONSE OF FIELD GROWN VEGETABLE CROPS TO DIFFERENT PLASTIC MULCH TREATMENTS

Introduction

Worldwide all agronomic and horticultural crops are under threat of insect pest attack.

Insect pests cause yield losses by direct feeding and oviposition, and indirectly by transmitting disease producing pathogens. In commercial production systems, chemical insecticides are the primary tools for dealing with the insect pests. However, frequent use of the same insecticides against same target insect pests has led to the development of resistance by the target pest (Gao et al. 2012). Moreover, repeated insecticide application causes the elimination of beneficial pollinators, predators and parasitoids resulting in resurgence of primary pests and the emergence of new pests (Jensen 2000a, Reitz and Funderburk 2012, Demirozer et al. 2012, Seal et al. 2013).

Insecticide residues contaminate crops and the environment and present a risk to human health

(Mostafalou and Abdollahi 2013). Increasing markets for organic and chemical-free produce warrant to adopt alternative integrated pest management (IPM) strategies, which maintain pest population below economic injury levels in an ecologically and economically justified manner

(Dent 1995, Kogan 1998, FAO).

Cultural tactics using plastic film mulches are one of the important components of an

IPM program. It has multiple benefits, including increasing the effectiveness of fumigation, increased soil temperature and moisture retention, reduced weed pressure and soil compaction, reduction of infestation by insect pests and diseases, cleaner harvested products, higher crop yields per unit area, earlier crop production, and more efficient use of irrigation by reducing soil evaporation and increase soil nutrient availability through reduced fertilizer leaching, and improved nutrient uptake (Emmert 1957, Hanlon and Hochmuth 1989, Lamont 1993, Kasirajan and Ngouajio 2012). The use of plastic mulch for vegetable production is a standard cultural

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practice in the United States and other developed countries and is increasing in developing countries (Castro et al. 1993, Vos et al. 1995, Hochmuth 1997, Kasirajan and Ngouajio 2012).

The US Environmental Protection Agency (EPA) estimates that, farmers use over 300 million acres of plastic mulch. The main fresh market vegetables those are grown on plastic mulch include bell pepper, muskmelon, eggplant, slicing cucumber, summer squash, tomato, beans and watermelon (Ngouajio et al. 2008, Nottingham and Kuhar 2016).

Light energy radiated from various colored plastic mulches can lead to modification of the plants microclimate by altering the spectral balance and quantity of light, root zone temperatures and soil moisture, and ambient temperature thereby influencing vegetative crop growth and yield (Liakatas et al. 1986; Decoteau et al. 1989, 1990; Fortnum et al. 1995; Díaz-

Pérez et al. 2007). Reflective foil mulch enhanced the growth of snap beans and Chinese cabbage compared to the bare soil (Wells et all. 1984, Zalom and Cranshaw 1981). Aluminized plastic mulch resulted in better survival of the tomato seedlings and increased growth compared to black plastic mulch (Schalk and Robbins 1987).) Plants growing above reflective plastic mulch grew more rapidly than did those without such mulch (Summers et al. 2004a, 2004b, and 2010). Vine length of watermelon and cucumber was longer in most mulched plots compared to the bare ground treatment (Soltani et al. 1995, Andino and Motsenboker 2004). Bell pepper grew better within metalized reflective mulches compared to black mulches (Díaz-Pérez 2010), although shoot dry weight of tomato was not affected by the mulch (reflective, black/black, black/white, white black plastic and paper) treatments (Suwwan et al. 1988). However, growth of tomato plants was inconsistent among reflective, blue, orange, yellow, white and black mulches

(Csizinsky et al. 1995).

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Various plastic film mulches have been effective in increasing yields or stimulating earlier fruiting. Aluminum or silver based reflective plastic mulch increased yields of summer squash, zucchini squash (Chalfant et al. 1977, Brown et al. 1993, Summers et al. 1995, Summers and Stapleton 2002a), pumpkin, cucumber (Brust 2000, Summers and Stapleton 2002a), strawberry (Rhainds et al. 2001), corn (Summers and Stapleton 2002b), cantaloupe and watermelon (Stapleton and Summers 2002, Summers et al. 2004, Andino and Motsenboker

2004) compared to a no mulch treatment. Field-grown pepper yields were also much higher on the UV- reflective mulches than on black plastic mulch (Reitz et al. 2003, Hutton and Handley

2007, Diaz-Perez 2010). Snap beans planted on reflective foil mulch were larger and had higher yields than plants grown on bare soil (Wells et al. 1984, Nottigham and Kuhar 2016). Number and weight of eggplant fruit were significantly greater on silver painted mulch than on black, red, or blue mulch or no mulch treatments in one study. However, in another study, apart from silver mulch, blue and white colored mulches produced more fruit number and a higher total yield although differences were not statistically significant (Mahmoudpour and Stapleton 1997).

Marketable yields of tomato increased on reflective mulches compared to bare ground and non-

UV reflective mulches (Scalk and Robbins 1987, Csizinsky et al. 1995, Riley and Pappu 2004,

Riely et al. 2012). Csizinszky et al. (1999) reported that, tomato yields in fall were similar between plants grown with UV-reflective mulches or white mulch. In another study, tomato fruit size and marketable yields were greater on plants with silver on white mulch than on the control black mulch. There were no significant differences in the quantity, quality, or earliness of tomato yields among white, black, silver based reflective and bare ground treatments (Brown and Brown

1992).

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Mostly positive findings on crops growth and yield were reported from reflective mulches but, colored mulches yielded mixed results. According to Mahmoudpur and Stapleton

(1997) “Response of plant’s growth and yield to different plastic film mulches may vary with plant taxa, seasonal conditions, climate, etc.” The present study was conducted to evaluate the effects of five plastic mulches and a no mulch control treatment on growth and yield of six vegetable crops in south Florida agroecosystem.

Materials and Methods

The study area, crop species, plastic mulches and their placement, field preparation, plot design, and crop establishment and management were described previously in Chapter 2.

Plant Growth and Biomass

Plant growth was evaluated based on plant height, width and dry weight. In 2015, height and width of the plant canopy were recorded on one date and in 2016 plants were measured on two dates. Plant height was measured from the surface of the soil to the tip of the topmost leaf on the vertical axis of the plant. To measure the width at the widest point of a plant, tips of two horizontally expanded foliage or branches from the stem were considered. In 2015, plant height and width were recorded on 30th December, which was 41 days after emergence (DAE) of bean, squash and cucumber, and 41 days after planting (DAP) of pepper, eggplant and tomato. In 2016, height and width were measured on 22, 23, 26 DAE for the first time, and 31, 37, and 38 DAE for the second time for squash, cucumber and snap beans, respectively. Pepper, eggplant, and tomato height and width were measured for the first time at 30 DAP, and for the second time at

41, 42, and 49 DAP for pepper, eggplants, and tomato, respectively. Five plants were randomly selected per sub-plot in each of the 4 replications; therefore, 20 plants were measured for each crop on each mulch treatment.

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Plant dry weight was determined only in 2016 experiment. Total plant dry weight was estimated by either collecting whole plants (roots, plus stems plus leaves) or roots and stems including leaves independently. For squash, snap beans, and cucumber; plants were collected on

56, 57, and 65 DAE, respectively from the middle of each subplot. From each subplot of 4 replications, three squash and cucumber and eight snap bean plants were randomly selected from four holes. All selected plants were pulled from the ground carefully keeping the roots intact.

Plants from the middle of each subplot were collected on 77, 81 and 93 DAP, respectively for pepper (3 plants per subplot), eggplant and tomato (2 plants per subplot). Plants were uprooted using a shovel to reduce the loss of roots and root hairs. Stems of each plant were then cut approximately at the soil surface using a clipper and kept in a paper bag labeled with mulch type and block number. Roots were placed in a plastic box marked with mulch type and block number. Afterwards, roots were carried to the laboratory facilities, placed on the screen and washed gently with tap water and brushes to remove the soil and debris. Finally, all samples were put in the paper bag marked with the mulch and replication and dried them in an oven at 60

0C until they maintained a constant weight. Dry weights were determined in gram with an electronic balance, PB3002-S (DeltaRange®), Switzerland.

Yield

Snap bean - All bean pods on 10 plants in five holes from the center of each subplot were hand-picked at pod maturity on 52 DAP both in the 2015 and 2016 experiments. After harvest, only marketable quality pods were separated and weighed in gram on the same day using a scale

(CCi scale company, Ventura, CA, USA).

Cucumber and squash – Marketable yield of cucumber and squash were assessed by harvesting fruit from five plants at the center of each subplot. Harvest was started when average fruit weight was about 150-200 gm and size was at least 2.36 cm. Harvest was continued every

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2-3 days until the plants died. For cucumber, six harvests were made in both 2015 and 2016. For squash, sixteen harvests were made in 2015. However, in 2016 only six harvests were made because some of the plants selected for harvest died from bacterial wilt disease. Deformed and unmarketable fruit were discarded at the time of harvest.

Tomato – Marketable yield was determined by collecting fruit from 10 plants in each mulch treatment. Fruit were harvested one time at 78 DAP in 2015 and two times at 68 DAP and

84 DAP in 2016. Fruit were graded as small, medium, large or extra-large using USDA standards for fresh market tomato according to Gross et al. (2016) and weighed.

Pepper – All plants on a sub-plot (15 plants) were harvested for evaluation of yield. In

2015, fruit were harvested four times to collect all marketable fruit and pepper weevil infested fruit and counted separately. In the 2016 fall planting, due to severe infestation of pepper weevil, both marketable and pepper weevil infested fruit were collected. Combined numbers (marketable plus infested) of fruit were used for statistical analysis.

Eggplant - Five plants from the center of each subplot were selected for harvest. Harvest was initiated at 89 DAP and continued for six times at 6-7 d interval. Fruit weight 450 to 700 gm were selected for harvest.

Data Analyses

Height and width data of each crop were analyzed separately for each measurement days.

Data were analyzed using a mixed model analysis of variance as fixed effects of mulch (PROC

GLIMMIX model, SAS Institute Inc. 2013, version 9.3, Cary, NC) followed by mean separation using the Tukey HSD (Honestly Significant Difference) procedure. Yield data of each crop were also analyzed using PROC GLIMMIX model in SAS. All the analysis was performed at 5% significance level. Untransformed means and standard error of the means are presented in the tables.

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Results

Height, Width and Dry Biomass

Snap beans

In 2015, plastic mulch treatments significantly increased height and width of snap bean as compared to the no mulch control treatment. Mean height and width were higher in reflective mulch treatments than in the other plastic mulch treatments (Table 4-1). In 2016, on 26 DAE plants were taller in the plastic mulch treatments than the no mulch treatment (F = 6.83; df = 5,

15; P = 0.002). However, width did not differ significantly among treatments although mean value was higher in silver on white reflective mulch compared to the no mulch treatment (Table

4-2). On 38 DAE, plants were taller and broader in the reflective mulch treatments than in the other treatments (Table 4-2). Root and shoot dry weight were also increased by all plastic mulch treatments. Dry weight of roots and shoots were significantly higher in plants grown in the reflective plastic mulch treatments plots than the non-UV reflective plastic mulch and no mulch treatments (F = 4.84; df = 5, 15; P = 0.008) (Table 4-3).

Jalapeno pepper

In 2015, mulch treatments did not affect height or width at 41DAP (Table 4-1). In 2016, height and width at 30 DAP were significantly lower in the white on black mulch treatments than in the other mulch and no mulch treatments (Table 4-2). At 41 DAP, compared to the no mulch treatment plastic mulch treatments had significantly broader plants. Among plastic mulch treatments, the black on white mulch treatment had the broadest plants (F = 5.22; df = 5, 15; P =

0.006) (Table 4-2).

Root dry weight in the mulch treatments differed slightly from that of the no mulch treatment (F = 6.05; df = 5,15; P = 0.003) (Table 4-3). Among the mulch treatments, the highest root dry weight was in the silver on white mulch and the lowest on no mulch treatment. Shoot

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dry weight was also influenced by mulch treatments and shoot dry weight was higher in all mulch treatments compared to no mulch treatment (F = 2.73; df = 5, 18; P = 0.04). The lowest dry weight was in the control treatment and the greatest plant dry weight was in the silver on white reflective mulch treatment followed by the silver on black and the other mulch treatments

(Table 4-3).

Eggplant

In 2015, the tallest plants were recorded from white on black mulch treatment.

Significantly broader plants were observed in all plastic mulch treatment compared with the no mulch control treatment (F = 10.90; df = 5, 15; P = 0.0001) (Table 4-1). In 2016, at 30 DAP, height and width were significantly higher in plastic mulch treatments than the no mulch treatment (Height: F = 5.43; df = 5, 15; P = 0.005, Width: F = 6.03; df = 5, 18; P = 0.002) (Table

4-2). Height and width at 41 DAP followed the same trend observed on 30 DAP (Table 4-2).

Compared with the no mulch treatment, there was significantly greater shoot dry weight in the reflective mulch treatments followed by the black on white, white on black and black on black plastic mulch treatments (Table 4-3).

Squash

In 2015, plastic mulch treatments significantly increased plant height and width (height: ranged from 37.1 ± 1.3 to 31.0 ± 0.5; width: ranged from 106.2 ± 1.3 to 92.7 ± 1.5). The smallest and tallest plants were recorded on the no mulch (height: 27.4 ± 0.8, width: 78.0 ± 4.6) treatment

(F = 13.12; df = 5, 15; P < 0.0001 for height; F = 5.09; df = 5, 15; P = 0.0063 for width) and reflective mulch treatments, respectively (Table 4-1).

In 2016, at 22 DAE and 31 DAE, plants were significantly smaller in the no mulch treatment than the plastic mulch treatments (31 DAE - height: F = 11.26; df = 5, 15; P = 0.0001, width: F = 13.57; df = 5, 15; P < 0.0001) (Table 4-2). Among the plastic mulch treatments, the

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plants were higher and broader in the silver reflective mulch treatments than in the standard white and black mulch treatments. Total plant dry weight (roots plus shoots) was also significantly higher in the plastic mulch treatments (ranging from 222.52 ± 5.28 to 270.18 ±

19.67 gm) than in the no mulch (147.25 ± 26.87 gm) treatment. Among mulch treatments, plants in the silver reflective mulches and white on black mulch had significantly greater total plant dry weight than in the black on black and black on white mulch treatments (F = 6.98; df = 5, 18; P =

0.0009) (Table 4-3).

Tomato

In 2015, height and width at 41DAP did not differ among treatments (P > 0.05) (Table 4-

1). Similarly, in 2016, at both 30 and 49 DAP height was not influenced by mulch treatments (P

> 0.05) (Table 4-2). Plants in the reflective mulch treatments were broader than those in the other mulch or no mulch treatments only at 30 DAP and did not vary among treatments at 49 DAP

(Table 4-2). Root and shoot dry weight in the mulch treatments did not differ that of the no mulch treatments (Table 4-3).

Cucumber

In 2015, vine length of the mulch treatments did not differ from that of the no mulch treatment (Table 4-1). In 2016, at 23DAE, plants in the plastic mulch treatments were consistently taller and broader than those in the no mulch treatment. The tallest and widest plants were found in the reflective mulch treatments (height: F = 12.54; df = 15,15; P < 0.0001, width:

F = 9.23; df = 5,15; P = 0.0004) (Table 4-2). At 38 DAE, vine length differences among treatments were similar to observations made at 23 DAE. Plants in the no mulch treatment had significantly fewer branches than those in the reflective mulch treatments (Table 4-2). Compared with the no mulch treatment and other plastic mulch treatments plants in the silver reflective

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mulch treatments had significantly greater dry weight. The lowest shoot dry weight was in the no mulch treatment (F = 7.84; df = 5,15; P = 0.0008) (Table 4-3).

Yield

Snap Beans

In 2015 and 2016, the mulch treatments had significantly higher yields (32% - 50%) than the no mulch treatment (Table 4-4). In 2015, the metalized silver on black plastic mulch treatment produced significantly more pods by weight than the other mulch treatments and no mulch treatment (F = 3.18; df = 5,18; P = 0.03). The average yield (weight) from the silver on black plastic treatment was about twice that of the weight of no mulch treatment. Yield in the silver on white, black on black, black on white, and white on black plastic mulch treatments were similar and approximately 32% higher than that of the control treatment (Table 4-4). In 2016, the silver reflective mulch treatments produced significantly higher yields than the other plastic mulch treatments or no mulch treatment (F = 9.19; df = 5, 18; P = 0.0002). The average yield from the no mulch treatment was two times less than that in the metalized mulch treatments

(Table 4-4).

Tomato

In 2015 and 2016, mulch treatment had no significant effect on the yield of tomato (Table

4-4). Mulch treatments produced higher yield than the no mulch treatment (Table 4-4). In 2016, the average yield was higher in the white on black mulch than in the other treatments (Table 4-

4). Yields from the first harvest indicated that there was no significant variation in producing early yield between mulch treatments and the no mulch treatment. However, 35% more yields were obtained from the mulch treatments than the no mulch treatment (Table 4-5).

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Eggplant

In 2016, the cumulative number of eggplant fruit did not differ among various treatments

(P > 0.05) (Table 4-4). However, there were significantly more early fruit in the silver on white, silver on black and white on black mulch treatments than in the black surfaced plastic or no mulch treatment (F = 5, 106.6; df = 5.38; P = 0.0002). In the subsequent harvests after first harvest, there were no significant differences among treatments (Table 4-5).

Cucumber

In each year, the number of marketable fruit were greater on plants in the reflective mulch treatments than in the non-metalized mulch and no mulch treatments (P < 0.05).

Significantly fewer fruit were produced by plants in the no mulch treatment than the mulch treatments (Table 4-4). Compared to the no mulch treatment fruit production on both reflective mulch treatments was about 46% and 70% higher in 2015 and 2016, respectively (Table 4-4).

However, fruit production on standard white on black mulch was 19 % and 42% higher than in the no mulch treatment in 2015 and 2016, respectively (Table 4-4). Earlier fruiting occurred in plants on all plastic mulch treatments compared to the no-mulch control treatment. However, earlier fruiting with a significantly greater number of fruit occurred in the reflective mulch treatments than in the other mulch treatments (Table 4-5).

Squash

In both years, relative to the no mulch treatment significantly greater numbers of fruit were produced by plants in plastic mulch treatments (F = 6.11; df = 5,15; P = 0.003) (Table 4-4).

Marketable fruit yields were approximately 20% higher in the silver reflective mulch than in the non-UV reflective plastic mulch treatments (Table 4-4). Earlier fruiting was also observed in plants in the plastic mulch treatments compared to no mulch treatment. Among plastic mulch

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treatments, the metalized plastic mulch treatments had significantly more fruit at the first harvest than the non-metalized mulch treatments (F = 10.93; df = 5, 108; P < 0.0001) (Table 4-5).

Jalapeno pepper

In 2015, except for the black on white mulch treatment, marketable yield was significantly higher in plastic mulch treatments than the no mulch treatment (F = 5.18; df = 5,15;

P = 0.006) (Table 4-4). Among plastic mulch treatments, the highest number of fruit were harvested from silver on black reflective mulch treatment, with the fewest fruit with pepper weevil infestation. In 2016, both marketable and unmarketable fruit numbers were significantly higher in silver mulch treatments than in the no mulch control treatment and other plastic mulch treatments. Significantly, less fruit were produced in the no mulch treatment compared to the other treatments (F = 26.91; df = 5,18; P < 0.0001) (Table 4-4).

Discussion

In both years, with the exception of tomato, more vegetative growth occurred in plants on the plastic mulch treatments than on the no mulch treatment. Root and shoot dry weight were also increased by mulch treatments. Among plastic mulch treatments, in most cases, most growth occurred in the reflective mulch treatments. These results are in agreement with the previous studies conducted by other authors. Ibarra et al. (2007) reported higher dry weight and leaf area of jalapeno pepper plants in plastic mulch treatments compared to plants in no mulch control plots. Increased vine length of watermelon in most mulched plots than in the bare ground treatment was documented by Soltani et al. (1995) and, Andino and Motsenboker (2004).

Positive growth effects of reflective mulch on various crops has been reported by other authors

(Zalom and Cranshaw 1981, Wells et all. 1984, Díaz-Pérez 2010, Summers et al. 2004b).

In the present study, mulch treatment did not affect height, width or stem and root dry weight of tomato, which agreed with previous studies conducted by Suwwan et al. (1988),

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Csizinszky et al. (1995), Csizinsky et al. (1999). However, Schalk and Robbins (1987) reported increased growth, based on plant height, of tomato plants on aluminized reflective plastic mulch than on the black plastic mulch. Andersen et al. (2012) reported higher stem dry weight of tomato plants grown in metalized and heat stripe mulch than in black mulch, which differs from our findings. This difference might be attributed to the difference in environmental factors, such as climate, soil and nutrient supply.

Plastic mulch increased yield of snap beans. In both years, plants in the metalized plastic mulch treatments produced more pods than the other treatments. The least pod by weight was harvested from no mulch plots. Similar results were reported by Wells et al. (1984) and

Nottigham and Kuhar (2016). There were no significant differences in the quantity and earliness of tomato yields among treatments. Similar results have been reported by (Suwwan et al. 1988,

Brown and Brown 1992, Graham et al. 1995 Csizinszky et al. 1999, Summers et al. 2010, Riely et al. 2012). December 1st harvest in 2017, yields of large and extra-large fruit were 35% more from mulch treatments compared to a no mulch treatment. Andersen et al. (2012) reported late flowering in tomato on black mulch compared to metalized or heat stripe mulch. However, the cumulative number of fruit were not impacted by mulch type.

Cumulative yields of eggplant fruit did not vary among treatments. However, early yield occurred in metalized mulch and white on black mulch treatments. Contrary to our results,

Mahmoudpour and Stapleton (1997) reported higher yields on silver painted mulch than in the other mulch and non-mulch treatments. We assume that distinct weather and soil condition might be reason of this variation in yield of eggplant. The impact of mulch color on the vegetative growth and yield has been assumed to be highly specific, and can vary with plant taxa, climate and seasonal conditions (Decoteau et al. 1988, Mahmoudpur and Stapleton, 1997).

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In our study, cucumber and squash yields were higher on plastic mulch with more fruit yield in metalized reflective mulch treatments earlier in the season which agrees with the finding of Brown et al. (1993), Brown and Boyhan (1996), Caldwell and Clarke (1999), Brust (2000),

Summers and Stapleton (2002a), Stapleton and Summers (2002), Summers et al. (2004a, 2004b),

Frank and Liburd (2005).

In 2015 and 2016, marketable pepper yield was significantly greater in the silver on black mulch than in the other mulch treatments. The lowest number of unmarketable fruit was obtained from the silver on black mulch treatment and highest from black on black plastic mulch treatment. The findings of Porter and Etzel (1982), and Reitz et al. (2003) support our findings.

The reflective silver mulch treatment produced significantly higher yield of bell pepper than standard black plastic mulch (Hutton and Handley 2007). Jalapeno pepper yield was 50% higher from plastic mulch treatments than the no mulch treatment (Ibarra et al. 2007).

In this study, the mechanisms involved driving differences in the growth and yield of vegetable crops due to mulch treatments were not explored. However, it has been reported that plastic mulches modify the crop microclimate under the mulch and as well as the ambient temperature at the top of mulch (Liakatas et al. 1986, Schalk and Robbins 1987, Tarara, 2000), which may have positive impact on crop growth and yield (Díaz-Pérez and Batal 2002, Lamont

2005, Ibarra-Jimenez et al. 2006). Radiated light energy from colored plastic mulches act with phytochrome and thus alter plants vegetative growth (Decouteau et al. 1989, 1990; Fortnum et al.

1995). Silver reflective mulches are able to create optimum root zone temperature (RZT), which may impact on the physiological processes such as gas exchange, and uptake of water and mineral nutrients which ultimately impact on the growth and yield (Cooper 1973, Tindall et al.

1990, Dodd et al. 2000, Díaz-Pérez and Batal 2002, Díaz-Pérez et al. 2007). Photosynthetically

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active radiation (PAR) reflected from mulches have a profound impact on the growth and yield of crops. It has been found that the rate of PAR reflected from UV reflective mulches were much higher than from the black or white plastic mulch or bare soil (Csizinsky et al. 1999, Summers et al. 2004, Díaz-Pérez 2010). Metalized reflective and white on black mulch maintain lower soil temperature than black mulch which is conducive for crop growth and yield (Ham et al. 1993,

Lamont 1993, Andersen et al. 2012). Based on the above information, we can speculate that some or all these factors may have played a role individually or in combination in influencing mulch effects on growth and yield of vegetable crops used in this study.

In conclusion, the results of this study indicate excellent potential for using reflective mulch for vegetable cultivation in south Florida to simultaneously increase growth and yield.

Other studies have shown that these mulches can reduce infestation of Thrips palmi (see

Chapter-2 and Chapter-3). However, economic analysis is needed to determine the costs and benefits of using reflective plastic mulches. Moreover, further study is needed to explore mechanisms behind the increase growth and yield of vegetable crops grown on plastic mulches.

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Table 4-1. Mean ± SE height and width (in cm) of six vegetable crops grown on different plastic mulches and a no-mulch in 2015 Crop Mulchx SB SW BB BW WB NM Height Snap Beans 38.1 ± 0.5ay 37.6 ± 2.0a 35.1 ± 1.3ab 34.5 ± 1.3ab 33.3 ± 0.8bc 30.5 ± 1.3c Pepper 22.9 ± 1.0a 22.9 ± 1.0a 23.6 ± 1.3a 24.4 ± 1.3a 18.8 ± 0.8a 19.8 ± 1.0a Eggplant 22.4 ± 1.3b 24.9 ± 1.0ab 22.2 ± 1.3b 22.1± 1.3b 31.2 ± 2.0a 21.6 ± 1.0b Squash 37.1 ± 1.3a 35.8 ± 0.8a 35.6 ± 0.8ab 34.0 ± 0.8ab 31.0 ± 0.5bc 27.4 ± 0.8c Tomato 61.7 ± 1.0a 62.5 ± 1.0a 60.2 ± 1.0a 58.9 ± 1.5a 61.7 ± 1.0a 59.4 ± 1.5a Cucumber 129.3 ± 3.8a 131.1 ± 3.3a 117.9 ± 3.6a 124.2 ± 3.3a 122.2 ± 3.8a 112.0 ± 3.8a Width Snap Beans 57.4 ± 1.0a 57.9 ± 1.0a 51.3 ± 1.0ab 53.3 ± 1.3ab 51.3 ± ab1.3 46.0 ± 1.0b Pepper 32.0 ± 1.0a 29.7 ± 1.3a 31.0 ± 1.3a 30.5 ± 1.3a 25.1 ± 1.0a 24.6 ± 1.3a Eggplant 46.2 ± 2.3a 52.3 ± 1.5a 41.4 ± 2.3a 44.7 ± 1.3a 44.7 ± 2.0a 27.7 ± 1.5b Squash 101.1 ± 1.0a 106.2 ± 1.3a 103.9 ± 1.5a 99.6 ± 1.8a 92.7 ± 1.5ab 78.0 ± 4.6b Tomato 85.1 ± 1.3a 85.1 ± 1.8a 84.1 ± 1.8a 83.6 ± 1.5a 84.8 ± 1.5a 79.2 ± 1.8a xSB-Silver on black, SW-Silver on white, BB-Black on black, BW- Black on white, WB- White on black, NM-No-mulch. yMeans within the same row followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

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Table 4-2. Mean ± SE height and width (in cm) of six vegetable crops grown on different plastic mulches and a no-mulch in 2016. Crop Mulchx SB SW BB BW WB NM First time Height Snap Beans 24.9 ± 0.5az 25.7 ± 0.5a 24.9 ± 0.5a 24.1 ± 0.5a 23.9 ± 0.5a 20.6 ± 0.5b Pepper 25.4 ± 0.3a 23.9 ± 0.5ab 24.4 ± 0.5ab 25.1 ± 0.5ab 22.6 ± 0.5b 23.1 ± 0.3ab Eggplant 20.3 ± 0.5a 20.6 ± 0.5a 21.8 ± 1.0a 20.6 ± 0.5a 19.8 ± 0.5ab 17.5 ± 0.5b Squash 20.8 ± 0.8a 21.6 ± 0.5a 18.8 ± 0.8a 19.8 ± 0.8a 18.3 ± 0.5ab 13.5 ± 0.8b Tomato 67.3 ± 1.0a 68.6 ± 0.8a 66.3 ± 1.3a 65.3 ± 1.3a 67.1 ± 0.8a 66.0 ± 1.0a Cucumber 16.5 ± 1.0a 17.8 ± 1.0a 14.0 ± 0.5ab 14.7 ± 0.8ab 11.9 ± 0.5bc 9.9 ± 0.3c Width Snap Beans 37.3 ± 0.8a 38.6 ± 1.0a 36.3 ± 1.0a 37.6 ± 1.0a 34.0 ± 1.3a 31.8 ± 1.3a Pepper 25.9 ± 0.8ab 26.2 ± 0.8ab 27.7 ± 0.8a 27.2 ± 0.8ab 22.6 ± 0.5b 24.4 ± 0.5ab Eggplant 40.1 ± 1.0a 41.4 ± 1.0a 39.6 ± 1.0a 40.4 ± 1.5a 36.8 ± 1.3ab 33.3 ± 1.3b Squash 61.0 ± 1.3a 64.3 ± 1.0a 58.0 ± 1.0a 55.6 ± 1.5a 55.4 ± 1.5a 36.8 ± 2.3b Tomato 65.8 ± 1.0a 62.5 ± 1.3b 61.0 ± 1.8b 56.9 ± 1.8c 57.4 ± 1.0c 55.9 ± 1.5c Cucumber 33.3 ± 1.0a 33.8 ± 1.3a 30.0 ± 1.3ab 29.5 ± 1.3ab 26.2 ± 0.8bc 21.6 ± 1.0c Second time Height Snap Beans 37.1 ± 0.3a 37.3 ± 0.8a 33.8 ± 0.8ab 34.8 ± 0.8ab 34.5 ± 0.8ab 29.7 ± 0.8b Pepper 36.3 ± 0.8a 36.5 ± 0.8a 36.3 ± 0.8a 35.8 ± 0.5a 34.3 ± 0.5a 32.5 ± 1.0a Eggplant 35.6 ± 0.5a 37.8 ± 1.0a 35.1 ± 0.8a 36.1 ± 0.8 a 32.8 ± 1.0a 25.7 ± 1.0b Squash 41.4 ± 1.0a 41.1 ± 1.0a 40.9 ± 1.3a 39.1 ± 1.3a 36.6 ± 1.3 a 26.7 ± 1.3b Tomato 90.2 ± 1.5a 92.5 ± 1.3a 91.2 ± 1.5a 91.7 ± 1.5a 88.4 ± 1.5a 88.1 ± 2.0a Cucumber* 111.8 ± 3.6a 111.5 ± 5.3a 92.2 ± 2.8ab 87.4 ± 2.8ab 83.1 ± 2.8bc 56.1 ± 3.8c Width Snap Beans 65.5 ± 1.5a 66.3 ± 1.3a 59.4 ± 1.3ab 60.2 ± 1.5ab 61.0 ± 1.5ab 51.1 ± 1.5b Pepper 37.6 ± 1.0ab 39.4 ± 1.0ab 38.6 ± 0.8ab 39.6 ± 0.8a 34.5 ± 1.0ab 33.5 ± 1.0b Eggplant 70.9 ± 1.5a 76.7 ± 1.8a 74.9 ± 1.5a 74.4 ± 1.5a 71.0 ± 2.0a 56.1 ± 2.3b Squash 115.6 ± 2.5a 115.3 ± 1.8a 100.3 ± 1.8a 102.1 ± 2.3a 98.8 ± 3.3a 69.6 ± 3.3b Tomato 99.1 ± 1.8a 99.3 ± 2.5a 105.4 ± 2.8a 96.8 ± 2.5a 95.0 ± 1.8a 96.3 ± 2.0a Cucumber** 4.9 ± 0.2a 4.7 ± 0.2a 4.2 ± 0.2ab 4.1 ± 0.2ab 4.1 ± 0.1ab 3.8 ± 0.1b xSB-Silver on black, SW-Silver on white, BB-Black on black, BW- Black on white, WB- White on black, NM- No-mulch. zMeans within the same row followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Cucumber-vine length. **Cucumber-branch number.

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Table 4-3. Mean ± SE dry biomass (in gm) of six vegetable crops grown on different five plastic mulches and a no-mulch in fall 2016. Crop Mulch Silver on black Silver on white Black on black Black on white White on black No mulch Roots plus shoots Snap Beans 93.7 ± 4.6abz 96.4 ± 3.9a 85.0 ± 4.1abc 71.8 ± 4.6bc 79.9 ± 6.6abc 69.3 ± 7.1c Cucumber 186.2 ± 23.6a 173.2 ± 25.7ab 104.6 ± 5.0c 113.6 ±1 5.9bc 105.2 ± 15.7c 87.1 ± 7.7c Squash 270.2 ± 19.7a 269.4 ± 12.3a 222.5 ± 5.3ab 229.6 ± 12.7ab 269.4 ± 12.3a 147.3 ± 26.9b Roots Pepper 35.4 ± 3.6ab 37.4 ± 3.8a 20.4 ± 0.8c 25.6 ± 3.0abc 26.6 ± 1.7abc 24.3 ± 2.6bc Eggplant 541.8 ± 47.8a 526.1 ± 30.3a 350.3 ± 20.7ab 455.6 ± 12.5ab 408.5 ± 25.6ab 278.4 ± 37.9b Tomato 20.0 ± 0.9a 20.6 ± 2.0a 17.2 ± 1.1a 18.1 ± 1.6a 18.9 ± 1.9a 17.6 ± 0.5a Shoots Pepper 236.8 ± 11.1ab 318.4 ± 19.0a 243.3 ± 35.3ab 233.5 ± 25.0ab 236.5 ± 14.8ab 206.9 ± 23.9b Eggplant 541.8 ± 47.8a 526.1 ± 30.3a 350.3 ± 20.7bc 455.6 ± 12.5ab 408.5 ± 25.6abc 278.4 ± 37.9c Tomato 467.6 ± 14.2a 613.6 ± 64.7a 577.7 ± 35.5a 591.4 ± 64.6a 523.5 ± 76.6a 475.6 ± 39.5a zMeans within the same row followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

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Table 4-4. Mean ± SE yields of six vegetable crops grown on different plastic mulches and a no-mulch in the Fall 2015 and 2016 Crop Mulchx SB SW BB BW WB NM Snap Beansy 2015 2.4 ± 0.2a** 1.9 ± 0.1ab 1.7 ± 0.2ab 1.9 ± 0.2ab 1.7 ± 0.4ab 1.2 ± 0.1b 2016 2.9 ± 0.1a 2.9 ± 0.1a 2.3 ± 0.2 ab 2.0 ± 0.1b 2.1 ± 0.3ab 1.5 ± 0.1b Pepperz 2015 Marketable 79.5 ± 19.9a 52.8 ± 12.1 ab 56.8 ± 11.3ab 22.0 ± 9.1b 54.0 ± 9.4ab 9.5 ± 2.3b Infested 6.5 ± 3.0b 24.2 ± 6.7ab 40.8 ± 8.1a 19.5 ± 4.9ab 24.8 ± 4.4ab 28.9 ± 7.3ab 2016 613.0 ± 58.8a 623.5 ± 43.0a 177.3 ± 17.9bc 181.5 ± 37.0bc 322.3 ± 58.0b 119.5 ± 33.2c Eggplantz 2016 34.5 ± 6.6a 28.0 ± 4.4a 22.0 ± 2.1a 25.0 ± 1.8a 29.5 ± 3.3a 26.0 ± 2.7a Squashz 2015 16.0 ± 1.3ab 19.0 ± 0.7a 19.0 ± 1.0a 13.3 ± 1.2b 17.5 ± 1.8ab 14.0 ± 1.1b 2016 19.8 ± 2.4a 20.5 ± 0.7a 15.8 ± 1.4a 15.0 ± 1.2a 16.5 ± 1.2a 8.5 ± 1.3b Cucumberz 2015 20.0 ± 1.8a 20.0 ± 1.2a 17.0 ±1.7ab 16.5 ± 1.9ab 13.3 ± 2.1ab 10.8 ± 2.3b 2016 27.3 ± 1.1a 23.3 ± 2.5ab 17.5 ± 1.3bc 16.3 ± 2.3bc 13.5 ± 1.0cd 7.8 ± 2.3d Tomatoy 2015 16.3 ± 0.7a 16.8 ± 1.7a 13.5 ± 1.7a 13.5 ± 2.3a 15.0 ± 1.1a 11.3 ± 1.8a 2016 47.1 ± 6.3a 44.3 ± 5.2a 45.4 ± 4.5a 50.3 ± 5.5a 54.6 ± 4.2a 44.7 ± 12.5a **Means within the same row followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. xSB-Silver on black, SW-Silver on white, BB-Black on black, BW- Black on white, WB- White on black, NM- No-mulch. yYield assessed based on weight (kg). zYield assessed based on marketable fruit number.

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Table 4-5. Mean ± SE yields of six vegetable crops grown on different plastic mulches and a no-mulch in the Fall 2015 and 2016. Crop Mulchx SB SW BB BW WB NM Tomatoa 2016 1.12.2017 19.4 ± 3.6ay 18.2 ± 2.0a 18.4 ± 3.0a 20.3 ± 0.9a 17.4 ± 1.0a 12.3 ± 6.2a 2.04.2017 27.7 ± 2.6a 26.1 ± 3.2a 27.0 ± 1.6a 30.0 ± 4.6a 37.2 ± 3.1a 32.4 ± 6.3a Eggplantz 2016 2.03.2017 8.0 ± 2.04a 6.0 ± 2.83ab 0.50 ± 0.29c 2.0 ± 0.71bc 6.75 ± 4.17ab 1.0 ± 0.0bc 2.12.2017 6.0 ± 2.34a 3.50 ± 1.44a 3.25 ± 0.85a 4.50 ± 0.96a 3.75 ± 1.75a 5.50 ± 1.32a 2.20.2017 5.0 ± 0.41a 4.25 ± 0.48a 4.0 ± 0.71a 4.75 ± 0.85a 4.0 ± 1.08a 5.0 ± 0.41a 2.28.2017 4.50 ± 1.32a 3.50 ± 0.96a 3.75 ± 0.85a 2.75 ± 0.48a 3.50 ± 1.71a 3.25 ± 0.75a 3.10.2017 6.0 ± 1.41a 6.50 ± 1.26a 4.50 ± 0.50a 5.50 ± 0.96a 5.25 ± 1.11a 4.50 ± 0.50a 3.24.2017 4.75 ± 1.11a 4.25 ± 1.32a 6.0 ± 0.91a 5.50 ± 0.65a 6.25 ± 1.89a 6.75 ± 1.11a Cucumberz 2015 1.02.2016 10.50 ± 5.19ab 11.0 ± 2.48a 4.00 ±1.23ab 6.75 ± 0.48ab 5.00 ± 1.23ab 2.25 ± 0.85b 2016 12.20.2016 1.5 ± 0.29ab 2.5 ± 1.19a 0.50 ± 0.5bc 0.25 ± 0.25bc 0.25 ± 0.25bc 0.0 ± 0.0c 12.24.2016 5.0 ± 1.68a 4.0 ± 1.08a 2.75 ± 0.25a 2.25 ± 0.48a 2.0 ± 0.41a 0.0 ± 0.0b 12.25.2016 2.25 ± 0.48a 1.75 ± 0.25ab 0.0 ± 0.0c 0.0 ± 0.0c 0.25 ± 0.25bc 0.25 ± 0.25bc 12.27.2016 6.75 ± 1.03a 4.50 ± 0.50ab 3.50 ± 1.26ab 5.25 ± 1.18ab 2.75 ± 1.11bc 0.5 ± 0.29c Squashz 2015 12.29.2015 17.0 ± 2.86a 16.25 ± 2.02a 6.75 ± 1.55b 6.75 ± 1.55b 7.00 ± 1.47ab 2.00 ± 1.35b 2016 12.16.2016 6.0 ± 1.23ab 7.75 ± 0.85a 3.25 ± 0.5bc 3.50 ± 0.87bc 6.0 ± 1.23bc 1.75 ± 0.85c 12.18.2016 3.0 ± 0.41a 3.0 ± 0.91a 2.0 ± 0.91a 2.0 ± 0.00a 2.0 ± 0.82a 1.0 ± 0.58a 12.20.2016 0.50 ± 0.23a 1.50 ± 0.87a 1.50 ± 0.50a 1.50 ± 0.96a 1.0 ± 0.96a 0.50 ± 0.29a yMeans within the same row followed by same letters are not significantly different according to Tukey’s HSD test at the level of P ≤ 0.05. xSB-Silver on black, SW-Silver on white, BB-Black on black, BW- Black on white, WB- White on black, NM- No-mulch. aYield assessed based on weight (kg). zYield assessed based on marketable fruit number.

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CHAPTER 5 COMBINED EFFECTS OF PLASTIC MULCH AND AMBLYSEIUS SWIRSKII ATHIUS- HENRIOT IN MANAGING MELON THRIPS, THRIPS PALMI KARNY (THYSANOPTERA: THRIPIDAE) ON FIELD GROWN VEGETABLE CROPS

Introduction

Melon thrips (Thrips palmi) is a serious pest of nearly all vegetable crops and ornamental plants grown in fields and greenhouses (Faust et al. 1992, Hollinger 1992, Seal and Baranowski

1992, Seal and Sabines 2012). There is a heavy reliance on chemical insecticides for controlling thrips (Morse and Hoddle 2006, Seal and Kumar 2010, Bao et al. 2014), and some reports have suggested a reduced susceptibility to many chemical insecticides. According to Seal et al. (2013), spinosad (Spintor®) was the most effective insecticide used by commercial growers to control T. palmi on vegetable crops until 2008. After 2008, growers started realizing the reduced effect of spinosad because of its frequent use for managing thrips. Currently, none of the commonly used insecticides satisfactorily control T. palmi when applied alone. Moreover, the adverse effects of applying insecticides suggests a need to employ biological control methods against T. palmi, as an economical and environmentally safe alternative to chemical pesticides (Cock et al. 2010).

A phytoseiid, Amblyseius swirskii Athius-Henriot (Acari: Phytoseiidae), is a generalist predatory mite that has become a well-known biological control agent following its introduction to the market in 2005. However, it has been used for biological control since 1962 (Messelink et al. 2008, van Lenteren 2012). It has the potential to control several pest species including whiteflies, western flower thrips, chilli thrips, broad mites, and spider mites in vegetable and ornamental situations (Brodsgaard and Stengaard 1992, Messelink et al. 2005, Arthurs et al.

2009, Stansly and Castillo 2009, Cock et al. 2010, Dogramaci et al. 2011, Calvo et al. 2012, van

Lenteren 2012, Xiao et al. 2012, Calvo et al. 2015). Blasco et al. (2012) reported that A. swirskii can successfully control the eggs and first instar nymphs of Asian citrus psyllids in the

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laboratory. Kakkar et al. (2016) reported that populations of T. palmi were reduced by A. swirskii in a cucumber field in Homestead, Florida. It has also been shown that A. swirskii is a more efficient thrips predator than Neoseiulus cucumeris (Oudemans) or Amblyseius degenerans

Berlese (Acari: Phytoseiidae), which are also commercially available (van Houten et al. 2005,

Messelink et al. 2006, Arthurs et al. 2009, Stansly and Castillo 2009, Reitz et al. 2011, Kakkar et al. 2016). Release of 20-25 A. swirskii per square meter can effectively control melon thrips in green house eggplant (Shibao et al. 2010). In a laboratory, a gravid female can consume 4-7 first instar larva of T. palmi (M. A. R. Personal observation). In Spain, A. swirskii has been used as a biological control agent for cucumber, eggplant, sweet pepper and zucchini grown in protected environmental conditions (Calvo et al. 2015). There are many successful examples of controlling thrips, whiteflies, and other insects using phytoseiid predatory mites including A. swirskii, but mostly in protected environments such as greenhouses and shade houses. A very few efforts were made to control melon thrips and other thrips species in field situations.

Specific color and reflectance properties of plastic mulches have the potential to deter or attract insects by influencing their behavior when they visit plants (Schalk and Robbins 1987,

Scott et al. 1989, Greenough et al. 1990, Csizinszky et al. 1999, Summers 2010, Antignus 2014,

Tyler-Julian et al. 2015). Mulches with metalized that reflect ultraviolet (UV) radiation have effectively been used to manage infestation and disease transmission from a wide variety of insects including thrips (Scott et al. 1989, Greenough et al.1990, Brown and Brown 1992, Reitz et al. 2003, Riley and Pappu 2004). Therefore, integrated pest management strategies combining a biological control agent A. swirskii and plastic (UV- reflective and various colored) mulches can be an alternative approach to manage melon thrips in filed grown vegetable crops.

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Little attention has been paid to investigate the effects of various colored and UV- reflective mulches on the existence and population dynamics of phytoseiid predators, although

UV-B radiation has the potential to impact the biology of predatory mites and the interactions between these mites and their prey (Onzo et al. 2010, Ghazy et al. 2016, Koveos et al. 2017).

Also, there are very few reports of the effects of colored and UV reflective plastic mulches on beneficial insects in field experiments. For example, honey bees visited squash plants more frequently when grown with aluminum or white material compared to non-mulched plots or black mulch (Moore et al. 1965, Wolfenbarger and Moore 1968). Simmons et al. (2010) found that abundance of the whitefly predator Delphastus catalinae (Horn) and parasitoid Eretmocerus sp were not affected by mulch color. Species diversity and density of predatory arthropod did not vary among living mulch, synthetic reflective and standard white mulch treatments (Frank and Liburd 2005, Nottingham and Kuhar 2016). However, aphid parasitism by Aphidius ervi

(Haliday) was affected by UV-reflection from aluminum foil mulch until foliar growth of

Chinese cabbage obscured the mulch (Zalom and Cranshaw 1981). In field-grown pepper, UV- reflective mulch significantly lowered the number of the predator Orius insidiosus (Say) compared with the black mulch treatments (Reitz et al. 2003). Several laboratory studies revealed the deleterious effects of UV-B radiation on the fecundity (Suzuki et al. 2009), embryonic development and survivability of phytophagous and predatory mites (Othsuka and

Osakabe 2009, Sakai and Osakabe 2010, Sakai et al. 2012, Fukaya et al. 2013, Koveos et al.

2017). Legarrea et al. (2010) reported that A. swirskii tend to evade the area of comparatively higher UV-B radiation. Therefore, we hypothesized that UV reflective mulch can hinder the predation efficiency and existence of A. swirskii.

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Knowledge on tritrophic interactions i.e., interactions between insect ecology and their host plants, and natural enemies are required to develop a successful integrated pest management program (van Lenteren and Noldus 1990). Phytophagous and predatory mites are inclined to create guilds in refuges of plant structure where intensity of UV-B radiation is attenuated, such as the abaxial surface of leaves (Ohtsuka and Osakabe 2009) or in the topmost stratum of plants

(Onzo et al. 2010). Neoseiulus cucumeris and A. swirskii were most abundant in the bottom third of greenhouse-grown sweet pepper (Fatnassi et al. 2015). Leaf domatium, trichome, hair and pubescence are important structures in host plants which determine the abundance of phytoseiid predators (O’Dowd and Willson 19991; Walter and O’Dowd 1992a, 1992b; Walter 1996;

McMurty and Croft 1997). Phytoseiid predators mainly exploit plant volatiles as a cue to trace prey patches (Margolies et al. 1997). The influence of UV reflective mulch and crop species on within-plant distributions and host preference of A. swiskii is largely unknown.

The purpose of this study was to investigate the combined effect of various plastic mulches and A. swirskii on melon thrips populations on field grown vegetable crops. We extended our effort to determine the effect of metalized UV-reflective and colored non-UV reflective mulches on the existence of A. swirskii in field-grown vegetable crops. Host preference and effects of crop and mulch on the within-plant distributions of A. swirskii are also reported.

Materials and Methods

Experiments were conducted in field research plots at the University of Florida, Tropical

Research and Education Center (TREC), Homestead, Florida, during the Fall of 2015 and 2016.

Procedures for field and bed preparation, mulch placement and crop maintenance were the same as described in Chapter 2.

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Field Design, Mulch and Crop Types for 2015 Experiment

Six vegetable crop species (eggplant, cucumber, squash, snap beans, jalapeno pepper, and tomato), five different plastic mulch treatments and a no mulch control treatment were also similar to Chapter 2. For field design, there were three blocks, each block consisted six beds

(main plots or whole plots), where each bed or whole plot represented one mulch treatment. Each whole plot was 54 m long, which was divided in-to 12 equal 3.05 m long subplots. Amblyseius swirskii were applied to six sub plots for six crops in the first half of each whole plot. There was a 1.52 m buffer between each subplot to minimize the dispersion of A. swirskii from one subplot to the next. Each of six different crop species was established in each subplot in the first half of a main plot. Similarly, six crops on the subplots were arranged in the second half of a whole plot and were considered as a no A. swirskii treated control. The field design was randomized complete block split plot, where mulch was the whole plot and crop was the subplot. A 91cm center to center spacing was maintained between main plots. Each block was separated by 3.05 m nonplanted fallow area to prevent the movement of A. swirskii.

Field Design, Mulch and Crop Types for 2016 Experiment

Mulch treatments were silver on white, silver on black, and the standard white on black.

The crops studied in 2016 were eggplant and cucumber. Randomized complete block split plot design was followed to place the plastic mulch and crop species where mulch was the whole plot and crop was the subplot. There were four blocks (replicates), each with three 22.86 m long parallel beds. Each whole plot was divided into four equal 4.57 m long sub plots (first two subplots for mite treatment on two crops and the next two for the control treatment) with a 1.52 m buffer in between sub plots. Within the block the whole plots were separated by 1.8 m distance from center of one bed to another to minimize the dispersion of A. swirskii. Crops were randomized within each plastic mulch treatment and mulch treatments were randomized within

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each block. Whole plot treatments consisted of two ultraviolet reflective mulch and a white on black mulch, subplot treatments consisted of cucumber and eggplant treated and untreated with

A. swirskii. Blocks were separated by 3.05 m of fallow soil, which was kept weed free mechanically throughout the experiments to prevent the dispersal of predators.

Crop Establishment

Crop establishment for 2015 experiment is described in Chapter 2. In 2016, cucumber was directly seeded, and eggplant was transplanted on the day of germination of cucumber. This timing of planting allowed both crops to have broad leaves with sufficient leaf area to placement of A. swirskii on the leaf on the day of first release.

Source and Maintenance of A. swirskii

Predatory mites, A. swirskii were supplied by Koppert Biological Systems Inc.

(www.Koppert.com). Upon arrival, mites were stored in a growth chamber maintained at 11 ±

10 C, 60± 5 % RH, and at 12h:12h (L: D) and release 24–48 h after arrival.

Prerelease Sampling and A. swirskii Application

In 2015, pre-release leaf sampling was done 24 h before the first phase release of A. swirskii to know the abundance of melon thrips in each crop. Sampling was done by collecting five fully expanded leaves randomly from middle third of five plants in each sub plot. Samples were processed and melon thrips adults and larvae were recorded as described in chapter 2.

Ten-fifteen mites were released on each plant by collecting roughly 0.10 gm of bran from the vermiculite using long forceps (Specimen-10-Forceps, Bioquip products, Inc., CA, USA) having a flat tip. Amount of bran and number of A. swirskii in the bran were standardized by collecting bran from vermiculite at least 10 times and counting A. swiskii under the stereomicroscope at 20x magnification. The number of mites per plant was increased to 40-50 by four releases on two consecutive days for each crop. In the first phase, A. swirskii was released

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on all crops seven weeks (49 DAP) after planting (curative release). A second release was performed four weeks after the first release (77 DAP) using the same number of A. swirskii and application methods as described for the first release. Second release was made only on Jalapeno pepper and eggplant because cucumber, snap beans and squash had died by that date. Tomato was excluded from the second release because A. swirskii did not establish on tomato after the first release. Amblyseius swirskii was released in the morning and afternoon to avoid high solar intensity. Release of A. swirskii during heavy rains and high wind were also avoided.

In 2016, the same method and numbers of A. swirskii were followed as in 2015. Contrary to 2015, A. swirskii were applied early in the season (preventive release) when population of melon thrips was low as determined by visual sampling. Prerelease visual sampling was performed by carefully checking the thrips on the lower surface of leaf. Five plants were selected randomly from each subplot for visual sampling. Mites were released when the abundance of melon thrips adults was 0-5/plant. The first release of A. swirskii was done 15 d after germination of cucumber and planting of eggplant. The second release was done 18 days after first release

(33 DAP).

Evaluation Method

In 2015, post-release sampling was done two weeks after the first release following the methods described in pre-release sampling. The number of the thrips and A. swirskii in each sample were recorded. For the second phase predator release, evaluation was done seven days after release of A. swirskii. The numbers of A. swirskii were recorded by collecting samples from the A. swirskii treated subplots to determine the host and mulch preference by A. swirskii.

In 2016, first evaluation was done two weeks after the first release by sampling five fully expanded leaves from five plants in each subplot. A second and third evaluation were done 10 d

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and 20 d, respectively, after the second release. In the second release, evaluation was done by sampling four fully expanded leaves from each subplot. Thrips palmi and A. swirskii recording method were the same as followed in 2015.

Within-Plant Distributions of A. swirskii

In 2015, within-plant distributions of A. swirskii was studied only in eggplant and jalapeno pepper 6 d after the second release and in 2016, in cucumber and eggplant 23 d after the second release. The numbers of thrips in each stratum were also recorded to correlate the numbers of A. swirskii with those of T. palmi. To assess within-plant distributions of A. swirskii, one leaf was collected from each of the pre-described (in Chapter 3) three strata (top, middle and bottom) of a plant in each A. swriskii treated sub-plot. Five plants were selected from each subplot for sampling in 2015 and four plants were selected in 2016. Leaf samples from each subplot were placed in a 1-L plastic cup marked with stratum, replication number, plastic mulch and crop types. All samples were transported to the TREC vegetable IPM laboratory and were processed according to the method described by Seal and Baranowski (1992) to separate melon thrips adults, larvae, and eggs, immatures and adults of A. swirskii.

Statistical Analyses

To evaluate the combined efficacy of plastic mulch and A. swriskii in managing melon thrips data were analyzed separately for the number of adults and larvae and the total numbers

(adults plus larvae) of melon thrips. To determine the within-plant distributions, and host and mulch preference of A. swirskii numbers of eggs, immatures (larva, protonymph and deutonymph) and adults were used for analyses. All data were subjected to square root transformation before statistical analyses to meet the assumption of normality. Data were analyzed using mixed model ANOVAs (PROC GLIMMIX model, SAS version 9.3, SAS

Institute Inc. Cary, NC, 2013). In the PROC GLIMMIX model, the method of Kenward-Roger’s

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was used to compute degrees of freedom. For adults, larvae, and total counts of T. palmi in each mulch and crop, when the F- value was significant, differences among means were determined by Tukey’s HSD (Honestly Significant Difference) procedure in SAS (SAS Institute, Inc. 2013).

All the data were analyzed at the 5% significance level. PROC CORR in SAS was performed to determine relationship between A. swirskii in different plant strata with melon thrips larvae.

Untransformed means and standard errors are presented in the tables.

Results

Effects of A. swirskii and Mulch Treatments on Melon Thrips

In 2015 at 49 DAP, there were no significant interactions between crop and mite, and mulch and mite treatments (P > 0.05) (Table 5-1). Amblyseius swirskii did not reduce the populations of adults, larvae or the total number of melon thrips compared with the no mite treatment from the same crop and same mulch treatment (Tables 5-1, 5-3, 5-5 and 5-7). The second release at 77 DAP showed that A. swirskii was effective in controlling the number of melon thrips populations (P < 0.05) (Table 5-1). Significantly reduced number of adults (F =

33.49; df = 1, 24; P < 0.0001), larvae (F = 32.41; df = 1, 46; P < 0.0001) and total thrips (F =

36.32; df = 1, 46; P < 0.0001) (Table 5-1) were recorded in the plots with A. swirskii relative to the plots with no mites released. The number of melon thrips adults and larvae were 75% and

73% lower, respectively in the mite treated plots compared with the control plots (Table 5-3).

There was a significant interaction between crop and mite treatment (P < 0.05). In both eggplant and pepper, melon thrips populations were significantly lower in the mite treated area than the untreated area (Table 5-5). There were no significant interactions between A. swirskii and mulch treatments (Table 5-1 and Table 5-7).

In 2016, preventive release of A. swirskii at 15 DAP and evaluated 15 days after release

(DAR) significantly reduced the number melon thrips larvae (F = 18.37; df = 1, 9; P = 0.002)

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and the total number of thrips (F = 14.36; df = 1, 27; P = 0.0008) compared with the control treatment. The mean number of larvae was 50% less in the mite treated plots then the untreated plots (Table 5-6). However, the number of adult thrips was not reduced significantly due to the mite treatment (Table 5-2 and Table 5-4). There were no significant interactions between mite and mulch treatments, and mite and crop treatments as well (Table 5-2). The number of thrips in each crop did not differ statistically from the control treatment. The number of thrips was also similar in the control and treated plots for each mulch treatment. The mean number of total thrips in the mite treatment was 47%, 45% and 37% fewer in the silver on black, silver on white and white on black mulch treatments, respectively than the control treatment (Table 5-8). Among three mulch treatments, mean number of thrips was lower in both reflective mulch treatments than the white on black mulch treatment.

For the second release of A. swirskii at 33 DAP, evaluated 10 DAR showed no impact of

A. swirskii in reducing the number of melon thrips. There were no significant interactions between mite and crop treatment or mite and mulch treatment (P > 0.05) (Table 5-2). In some instances, the mean number of larvae and the total number of melon thrips were higher in the mite treated plots than the control treatment for each crop and mulch treatments (Table 5-4,

Table 5-6, and Table 5-8).

In the second release of A. swirskii at 33 DAP, evaluated at 20 DAR showed a marginal effect in reducing the number of melon thrips adults (F = 5.25; df = 1, 36; P = 0.03), larva (F =

4.34; df = 1, 36; P = 0.04), and total number (F = 5.75; df = 1, 36; P = 0.02) (Table 5-2 and

Table 5-4). Interaction effects between mite and crop treatments, and mite and mulch treatments followed the same pattern as was at 10 DAR of second release (Table 5-2). The mean number of melon thrips adults, larvae and the total number did not differ between the no A. swirskii treated

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control and treated plots for each crop in each of plastic mulch treatment (Table 5-6 and Table 5-

8).

Crop and Mulch Effects on A. swirskii

In 2015, there was no significant interaction between crop and mulch treatment for the number of A. swirskii (P > 0.05) (Table 5-9). However, crop type had a significant effect on the density of A. swirskii (F = 6.29; df = 5, 10; P = 0.007). The total number (adults plus immatures) of A. swirskii were significantly higest in eggplant and cucumber followed by squash, jalapeno pepper and snap beans. There were no A. swirskii adults or immatures on tomato (Table 5-10).

There was no difference in the mean number of A. swirskii among mulch treatments (Table 5-

11).

In 2016, sampling at 15 DAR of first release demonstrated that, except for the number of eggs, there was no significant effect of crop or mulch treatments on the number of A. swirskii.

The mean number of A. swirskii adults, immatures and the total number of mites were statistically similar both in cucumber and eggplant and in each mulch treatment (Table 5-10 and

Table 5-11). The second release of A. swirskii at 33 DAP, evaluated 10 DAR showed a significant effect of crop on the abundance of A. swirskii (Table 5-9). The mean number of A. swirskii adults (F = 66.14; df = 1, 9; P < 0.0001), immatures (F = 79.73; df = 1, 9; P < 0.0001) and the total number of mites were significantly higher in eggplant than in cucumber. There were no significant effects of mulch treatment alone or mulch and crop treatment combined (Table 5-

9, Table 5-10 and Table 5-11). At 20 DAR, effects of crop and much independently and their interaction was similar at 10 DAR (Table 5-9, Table 5-10 and Table 5-11).

Crop and Mulch Effects on the Within-Plant Distributions of A. swirskii

In both 2015 and 2016, stratum within the crop had a significant effect on the distribution of A. swirskii (P < 0.0001) (Table 5-12). In 2015, there was no significant interaction between

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crop and stratum (F = 2.65; df = 2, 48; P = 0.08); however, interaction was observed in 2016 for the number of adults and the total number of A. swirskii (Table 5-12). There was a significant interaction between mulch treatment and stratum in 2015 (P = 0.008); however, in 2016 there was no significant interaction (Table 5-12). In each year, in every crop and mulch treatment, the average numbers of A. swirskii were significantly higher in the bottom stratum than the middle stratum. The fewest A. swirskii were observed in the top stratum (Table 5-13 and Table 5-14). In each year, the number of A. swirskii were positively correlated with the number of melon thrips larvae in each stratum (2015: Pearson correlation coefficients, r =0.40, P < 0.0001; 2016:

Pearson correlation coefficients, r = 0.35, P < 0.0023).

Discussion

In 2015, curative release at 49 DAP, A. swirskii did not reduce melon thrips adults and larvae in all mulch treatments for all crops. This may be because the time for A. swirskii populations to increase to a sufficient density to cope with prey populations. Arévalo et al.

(2009) reported that both preventive and curative releases of Amblyseius cucumeris (Oudemans)

(Acari: Phytoseiidae) alone or in combination with Orius insidiosus Say (Hemiptera:

Anthocoridae) did not provide control of flower thrips in blueberry due to the short period prey populations were available in the field was not sufficient to build up the population for natural enemies. In the present study, by the time A. swirskii were released, the population of melon thips was highly abundant. Density of melon thrips (adult plus larva) per five-leaf sample were

2016, 1415, 728, 273, 63 and 20 in eggplant, cucumber, squash, snap beans, pepper, and tomato, respectively. Moreover, there was a heavy rain (0.36 inch) during the week we released the mites which could have hindered the population buildup of A. swirskii although prey was highly abundant. Environmental factors such as temperature, relative humidity and rainfall, and starvation in natural environments can inhibit in the population buildup of arthropod

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communities (Wolda 1978, Yaninek et al. 1989, Ghazy et al. 2016). The number of A. swirskii recovered from each crop was very low (Table 5-10). Therefore, we assume that the number of

A. swirskii were very low respect to the number of thrips. Therefore, the mites were unable to control melon thrips populations effectively. Contribution of natural enemies in the suppression of field populations of thrips is insignificant because biological attributes of thrips help to prevail over the characteristics of natural enemies (Mound and Teulon 1995, Parella and Lewis 1997).

After the second release at 77 DAP (29th February, 2016), melon thrips were controlled by A. swirskii. In the late season when leaves of crops senesced and temperature went up (30-32 oC), thrips population abundance went down naturally, which was effectively managed by A. swirskii. Another reason might be the natural occurrence of Orius insidiosus in the study area.

We observed 5-10 Orius insidiosus in almost all samples of eggplant and pepper. Orius is an efficient predator of T. palmi (Seal 1997). In the previous studies, Orius insidiosus effectively reduced Frankliniella thrips in field-grown pepper (Funderburk et al. 2000, Ramachandran et al.

2001) and chilli thrips in greenhouse grown pepper (Doğramaci et al. 2011). Therefore, significant reduction of melon thrips compared to the control treatment might be due to the combined predation effect of A. swirskii and Orius insidiosus.

In 2016, the number of melon thrips larvae and total number of thrips was reduced in response to the preventive release of A. swirskii at 15 DAP when population density of melon thrips was low. There are several studies which demonstrated that A. swirskii lowered the number of thrips species infesting vegetable crops in green house, shade house or semi-filed situations where thrips population density was low (Arthurs et al. 2009, Messelink et al. 2008,

Calvo et al. 2011, Dogramaci et al. 2011, Kakkar et al. 2016). In the A. swirskii treated plots, we did not observe a significant reduction of melon thrips adults. This could be due to the mobility

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of melon thrips adults. Thrips adults immediately leave their present location once it is touched.

Moreover, adult T. palmi were not preyed upon by A. swirskii in a choice test (M. A. Razzak personal observation). Again, A. swirskii failed to manage T. palmi when population density went up after the second release in 2016 (sampled 10 DAR) which is supported by the results at

49 DAP releases in 2015. Assessment at 20 DAR of second release showed that A. swirskii reduced the number of T. palmi which is similar to the findings of Kakkar et al. (2016).

Mulch treatment did not affect the existence of A. swirskii, although numerous laboratory studies revealed the deleterious effect of UV-B on egg production, hatching, and survivability of immatures, and adult phytophagous and predatory mites. However, in many cases laboratory study do not translate into the natural environment. In the laboratory, organisms are exposed to specific doses of UV continuously for a specific time period which is not the case in the natural environment. Moreover, mites tend to evade the area of high UV radiation behaviorally

(Legarrea et al. 2010), inhabiting underside of the leaves as well domatia of the leaves (Suzuki et al. 2009, Othsuka and Osakabe 2009), hiding in different plant parts (Onzo et al. 2010).

Photoreactivation system of the cuticular carotenoids of phytophagous and predatory mites are reported to aid in UV-B tolerance (Fukaya et al. 2013, Koveos et al. 2017).

In the present study, A. swirskii established on all crops except tomato. Tomato may not be a preferable host to A. swirskii and melon thrips or it might be due to the insufficient number of prey available. In chapter two, it was reported that tomato is the least preferable host to melon thrips. Very few larvae were observed in tomato leaf samples. Moreover, among the six vegetable crops in this study, tomato leaves had the highest number of glandular trichomes per unit area (Chapter-2). Higher densities of glandular trichomes impede the movement of spider mites and A. swirskii, which was considered as an indicator of repellence property of tomato

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(Maluf et al. 2007, van Houten et al. 2013). An allelochemical (α- tomatine) in tomato has been reported to be a deterrent of thrips (Hirrano et al. 1994). Coll and Ridgway (1995) reported that

Orius spp. do not readily buildup population on tomato. However, a one season study is probably not sufficient enough to make a definitive statement on the establishment efficiency of A. swirskii on tomato.

In the present study, the highest number of A. swirskii were found in eggplant followed by cucumber. Squash, snap beans and jalapeno pepper were equally preferable to A. swirskii. A higher number of non-glandular trichomes and domatia are attributed to offer a competitive advantage in prey searching, feeding, mating, oviposition and hiding of phytoseiid predators.

Leaves with domatia had more diverse and greater densities of a phytoseiid species relative to leaves without domatia (O’Dowd and Willson 19991; Walter and O’Dowd 1992a, 1992b; Walter

1996). Domatia are also reported to offer a refuge and protect from top predators, biotic and abiotic stress (Schmidt 2014, Ghazy et al. 2016). The number of eggs, immatures and adults of phytoseiid predators Kampimodromus aberrans and A. swirskii were positively correlated with the trichome and domatia densities (Barret and Kreiter 1995, Kreiter et al. 2002, Avery et al.

2014). In the present study, trichome densities were similar in eggplant, cucumber and squash

(Chapter 2, Table 2-15). However, in eggplant each trichome has six radiating bars (stellar shaped trichome) which created a denser structure and might have provided more benefit respective to predation, escape from biotic and abiotic stress. In chapter two it was reported that the prey (T. palmi) densities are higher in eggplant than in cucumber. Higher prey densities could be another driving factor in the preference for eggplant over cucumber. Volatile organic compounds emitted by plants infested with the pest species act as a cue for arthropod predators and parasitoid to attack their prey (Sabelis et al. 2005, Arimura et al. 2009). Because of lacking

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proper eyes or visual sensory structures, phytoseiid predators mainly exploit plant volatiles as a cue to trace prey patches (Margolies et al. 1997). Uefune et al. (2010) reported that

Wollastoniella rotunda (Hemiptera: Anthocoridae) was attracted to higher densities of T. palmi in a Y-tube olfactometer experiment. It is not clear why cucumber was preferable to squash although the trichome densities were similar in both crops. Further study is needed to more thoroughly elucidate the host preference of A. swirskii.

In the present study, a higher number of A. swirskii was found in the bottom stratum followed by the middle stratum of each crop and mulch treatments. The topmost stratum had the fewest number of A. swirskii. The top stratum was comprised of smaller leaves and exposed to direct sunlight which might contributed to leaf area with unpreferable range of moisture to A. swirskii as compared to the other strata. The number of prey larvae was also less on the top stratum. Weintraub et al. (2004) observed that Neoseiulus cucumeris remained mostly in the bottom and middle section of the plants. Fatnassi et al. (2015) also reported the higher number of

A. swirskii and N. cucumeris in the bottom and middle strata of greenhouse grown sweet pepper because of higher humidity resulting from a higher transpiration rate compared with top stratum.

They conducted their study in absence of prey. The present study showed that the number of A. swirskii were positively correlated with the number of T. palmi larvae.

Overall, there were no significant effects of plastic mulch treatment, either UV reflective or non-UV reflective on the within plant distributions of A. swirskii, although we presumed that

UV- reflection could impact on the within plant distribution. Onzo et al. (2010) reported that during day time, predatory mites Typhlodromalus aripo hide in the apex of cassava plants to protect them from the deleterious effects of solar UV. Our study is the first report on the effects

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of different plastic mulch treatments on within-plant distribution of A. swirskii in different field- grown vegetable crops.

We conclude that the curative release A. swirskii is not effective for managing melon thrips in field-grown vegetable crops. Preventive release performs better than curative release but eventually still unable to control the prolific growth of melon thrips. Inclement weather such as heavy rainfall is an impediment to the population buildup of A. swirskii. UV reflection from metalized mulches apparently did not prove harmful for establishment A. swirskii, which suggest that the UV reflective mulch could be integrated with this predatory mite in a semi-field agroecosystem. Preventive method with UV reflective mulch and weekly releases of greater numbers of A. swirskii should be repeated for more definitively asses its effectiveness as a control measure. Host preference and within-plant distribution information will be helpful for improving thrips management by releasing A. swiskii into the field. Overall, the information generated from this study will be helpful for developing environmentally friendly management program for melon thrips or other thrips species.

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Table 5-1. ANOVA assessing the effects of A. swirskii and different mulch treatments on the abundance of melon thrips in different vegetable crops, 2015. Effect Thrips stage Adult Larva Total df F P df F P df F P *First release, 49 DAP Mite treatment 1, 142 1.38 0.24 1, 22 1.02 0.32 1, 22 1.18 0.29 Crop × Mite treatment 5, 142 1.17 0.33 5, 120 0.99 0.43 5, 120 1.15 0.34 Mulch × Mite treatment 5, 142 0.21 0.96 5, 22 0.43 0.82 5, 22 0.38 0.86 Crop × Mulch × Mite treatment 25, 142 0.62 0.92 25, 120 0.24 0.99 25, 120 0.24 0.99

**Second release, 77 DAP Mite treatment 1, 24 33.49 < 0.0001 1, 46 32.41 < 0.0001 1, 46 36.32 < 0. 0001 Crop × Mite treatment 1, 24 35.91 < 0.0001 1, 46 22.02 < 0.0001 1, 46 24.90 < 0.0001 Mulch × Mite treatment 5, 24 0.68 0.64 5, 46 0.76 0.58 5, 46 0.75 0.59 Crop × Mulch × Mite treatment 5, 24 0.43 0.82 5, 46 0.80 0.55 5, 46 0.74 0.60 *Released on six vegetable crops. **Released on two vegetable crops.

Table 5-2. ANOVA assessing the effects of A. swirskii and three different mulch treatments on the abundance of melon thrips in cucumber and eggplant, 2016. Effect Thrips stage Adult Larva Total df F P df F P df F P *First release, 15 DAP Mite treatment 1, 36 1.25 0.27 1, 9 18.37 0.002 1, 27 14.36 0.0008 Crop × Mite treatment 1, 36 2.45 0.13 1, 18 1.33 0.26 1, 27 3.86 0.06 Mulch × Mite treatment 2, 36 0.0 1.0 2, 9 0.94 0.43 2, 27 0.18 0.84 Crop × Mulch × Mite treatment 2, 36 2.48 0.1 2, 18 0.01 0.99 2, 27 1.04 0.37

**First sampling in the second release, 33 DAP Mite treatment 1, 33 0.26 0.61 1, 36 1.66 0.21 1, 36 1.52 0.22 Crop × Mite treatment 1, 33 0.27 0.61 1, 36 2.81 0.10 1, 36 2.67 0.11 Mulch × Mite treatment 2, 33 0.54 0.59 2, 36 2.67 0.08 2, 36 2.62 0.08 Crop × Mulch × Mite treatment 2, 33 2.45 0.10 2, 36 0.42 0.66 2, 36 0.53 0.59

***Second sampling in the second release Mite treatment 1, 36 5.25 0.03 1, 36 4.34 0.04 1, 36 5.75 0.02 Crop × Mite treatment 1, 36 0.21 0.65 1, 36 0.98 0.33 1, 36 0.96 0.33 Mulch × Mite treatment 2, 36 0.96 0.39 2, 36 0.92 0.41 2, 36 1.12 0.34 Crop × Mulch × Mite treatment 2, 36 1.30 0.28 2, 36 3.43 0.04 2, 36 3.67 0.03 *Evaluation performed 15 DAR (days after release) **Evaluation performed 10 DAR ***Evaluation performed 20 DAR

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Table 5-3. Mean ± SE number of melon thrips (T. palmi) with the effect of A. swirskii, regardless of crop and mulch, 2015. Thrips stage Adult Larva Total control treated control treated control treated First release, 49 DAP 91.49 ± 9.68az 102.46 ± 10.90a 982.73 ± 105.46a 1077.63 ± 117.79a 1074.22 ± 113.50a 1180.09 ± 125.99a

Second release, 77 DAP 8.69 ± 1.65az 2.19 ± 0.37b 74.67 ± 17.21a 19.86 ± 3.73b 83.36 ± 18.66a 22.06 ± 4.0b zMeans within the same row followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

Table 5-4. Mean ± SE number of melon thrips (T. palmi) with the effect of A. swirskii, regardless of crop and mulch, 2016. Thrips stage Adult Larva Total control treated control treated control treated First release, 15 DAP 67.0 ± 18.07az 58.0 ± 17.20a 141.21 ± 22.65a 65.92 ± 10.31b 208.21 ± 36.26a 123.92 ± 22.39b

First sampling in the second release, 33 DAP 125.0 ± 17.27a 115.71 ± 15.72a 2077.50 ± 457.71a 2684.25 ± 584.69a 2202.50 ± 466.86a 2799.58 ± 593.24a

Second sampling in the second release 177.50 ± 32.11a 128.75 ± 24.73b 1433.33 ± 125.53a 1214.17 ± 134.27b 1610.83 ± 131.82a 1342.92 ± 147.99b zMeans within the same row followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

Table 5-5. Mean ± SE number of melon thrips (T. palmi) in different crops with the effect of A. swirskii, regardless of mulch, 2015. Crop Thrips stage Adult Larva Total control treated control treated control treated First release, 49 DAP Cucumber 187.3 ± 18.3** 231.8 ± 21.8 1270.0 ±115.4 1541.1 ± 115.9 1448.3 ± 119.6 1772.9 ± 114.4 Eggplant 200.5 ± 17.7 196.7 ± 17.5 2075.6 ± 154.3 2056.4 ± 200.2 2276.1 ± 167.9 2253.1 ± 207.4 Squash 147.5 ± 17.6 162.7 ± 19.9 2393.3 ± 192.9 2716.7 ± 237.9 2540.8 ± 204.4 2879.4 ± 249.3 Snap Beans 16.9 ± 2.0 18.4 ± 1.9 136.1 ± 12.9 127.6 ± 11.9 153.0 ± 14.5 146.0 ± 13.1 Pepper 3.8 ± 0.6 3.9 ± 0.8 16.9 ± 1.9 18.6 ± 2.7 20.8 ± 2.1 21.9 ± 2.8 Tomato 1.9 ± 0.3 1.7 ± 0.4 4.5 ± 0.8 5.5 ± 1.2 6.4 ± 0.9 7.2 ± 1.4

Second release, 77 DAP Eggplant 16.6 ± 2.0az 3.8 ± 0.5b 145.4 ± 25.1a 37.5 ± 4.6b 161.9 ± 26.6a 41.3 ± 4.7b Pepper 0.8 ± 0.2az 0.6 ± 0.2b 4.0 ± 0.4a 2.2 ± 0.3b 4.8 ± 0.4a 2.8 ± 0.3b **Means within the same row are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. zMeans within the same row followed by the different letter are significantly different at P ≤ 0.05 according to Tukey’s HSD test.

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Table 5-6. Mean ± SE number of melon thrips (T. palmi) in cucumber and eggplant with the effect of A. swirskii, regardless of mulch, 2016. Thrips stage Adult Larva Total control treated control treated control treated First release, 15 DAP* Cucumber 40.83 ±14.81 59.75 ± 29.22 68.58 ± 11.45 34.58 ± 10.85 109.42 ± 22.39 94.33 ± 33.86 Eggplant 93.17 ± 31.97 56.25 ± 19.61 213.83 ± 32.49 97.25 ± 12.18 307.00 ± 56.76 153.50 ± 28.11

First sampling in the second release, 33 DAP* Cucumber 95.0 ± 19.40 80.58 ± 20.16 2187.50 ± 805.04 2235.17 ± 798.59 2282.50 ± 817.12 2315.75 ± 811.07 Eggplant 155.0 ± 26.89 150.83 ± 20.06 1967.50 ± 475.18 3133.33 ± 869.03 2122.50 ± 492.56 3284.17 ± 878.22

Second sampling in the second release, 33 DAP* Cucumber 227.50 ± 59.73 179.17 ± 43.70 1081.67 ± 137.02 1063.33 ± 240.55 1309.17 ± 180.12 1242.50 ± 276.40 Eggplant 127.50 ± 17.02 78.33 ± 13.59 1785.00 ± 156.95 1365.00 ± 115.74 1912.50 ± 153.88 1443.33 ± 115.57 *Means within the same row are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

Table 5-7. Mean ± SE number of melon thrips (T. palmi) in different mulches with the effect of A. swirskii, regardless of crop, 2015. Mulch* Insect stage Adult Larva Total control treated control treated control treated First release, 49 DAP** SB 86.4 ± 20.7 83.8 ± 23.6 910.0 ± 228.3 901.4 ± 219.9 996.4 ± 245.9 985.3 ± 238.4 SW 88.3 ± 23.6 110.7 ± 30.0 1015.8 ± 249.1 1113.1 ± 306.0 1104.2 ± 266.5 1223.8 ± 324.7 BB 88.1 ± 22.4 99.9 ± 24.7 946.4 ± 257.3 1198.4 ± 297.5 1034.6 ± 275.0 1298.3 ± 317.1 BW 102.4 ± 27.1 108.5 ± 26.0 991.1 ± 263.9 1156.1 ± 286.2 1093.5 ± 286.4 1264.6 ± 309.1 WB 103.6 ± 30.0 129.4 ± 36.9 1153.6 ± 332.3 1091.9 ± 343.2 1257.2 ± 359.6 1221.3 ± 371.6 NM 80.1 ± 19.8 82.4 ± 19.9 879.4 ± 238.3 1004.7 ± 300.6 959.4 ± 254.6 1087.8 ± 314.4

Second release, 77 DAP** SB 8.3 ± 4.2 1.7 ± 0.8 46.3 ± 28.8 18.2 ± 9.2 54.7 ± 32.9 19.8 ± 9.9 SW 9.0 ± 3.9 2.2 ± 1.0 70.5 ± 39.1 26.2 ± 11.6 79.5 ± 42.6 28.3 ± 12.4 BB 12.3 ± 5.6 3.2 ± 1.5 115.3 ± 67.2 16.5 ± 7.8 127.7 ± 72.5 19.7 ± 9.3 BW 9.8 ± 4.9 1.7 ± 0.7 87.0 ± 50.5 16.8 ± 7.9 96.8 ± 54.6 18.5 ± 8.5 WB 6.3 ± 3.5 2.5 ± 0.6 37.0 ± 17.8 12.8 ± 5.7 43.3 ± 20.8 15.3 ± 5.8 NM 6.3 ± 3.5 2.0 ± 0.9 91.8 ± 42.8 28.7 ± 13.0 98.2 ± 45.8 30.7 ± 14.0 * Silver on black (SB), Silver on white (SW), Black on black (BB), Black on white (BW), White on black (WB), and No mulch (NM). **Means within the same row are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

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Table 5-8. Mean ± SE number of melon thrips (T. palmi) in different mulches with the effect of A. swirskii, regardless of crop, 2016. Mulch* Insect stage Adult Larva Total control treated control treated control treated First phase release, 15 DAP** SB 18.6 ± 3.9 13.1 ± 3.3 108.8 ± 37.8 54.8 ± 18.4 127.4 ± 42.6 68.1 ± 20.6 SW 18.9 ± 2.5 11.3 ± 1.5 119.5 ± 21.7 63.9 ± 13.1 136.4 ± 22.7 75.1 ± 13.8 WB 165.5 ± 33.4 149.4 ± 33.4 195.4 ± 50.3 79.1 ± 22.3 360.9 ± 75.6 228.5 ± 44.5

First sampling in the second release, 33 DAP** SB 125.0 ± 33.5 80.1 ± 17.2 821.3 ± 112.9 800.5 ± 161.1 946.3 ± 144.2 880.6 ± 170.1 SW 77.5 ± 12.2 94.5 ± 22.2 991.3 ± 149.1 967.3 ± 233.2 1068.8 ± 160.0 1061.8 ± 241.5 WB 172.5 ± 32.0 172.5 ± 30.6 4420.0 ± 923.1 6285.0 ± 716.8 4592.5 ± 936.5 6457.5 ± 716.2

Second sampling in the second release, 33 DAP** SB 121.3 ± 16.1 93.8 ± 17.4 1285.0 ± 265.5 1117.5 ± 194.9 1406.3 ± 266.4 1211.3 ± 189.6 SW 136.3 ± 28.0 57.5 ± 7.7 1293.8 ± 181.2 925.0 ± 242.3 1430.0 ± 179.0 982.5 ± 241.4 WB 275.0 ± 84.1 235.0 ± 56.1 1721.3 ± 185.0 1600.0 ± 215.6 1996.3 ± 190.8 1835.0 ± 257.0 * Silver on black (SB), Silver on white (SW), and White on black (WB). **Means within the same row are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

Table 5-9. ANOVA assessing the effects of crops and mulch on the abundance of A. swirskii, regardless of mulch. Effect Mite’s stage Adult Immature* Egg Total df F P df F P df F P df F P 2015 First release, 49 DAP** Crop ------5, 10 6.29 0.007 Mulch ------5, 60 0.81 0.55 Crop × Mulch ------25, 60 1.14 0.33

2016 First release, 15 DAP Crop 1, 18 0.42 0.52 1, 18 1.04 0.32 1,9 14.06 0.005 1, 9 2.61 0.14 Mulch 2, 18 3.04 0.07 2, 18 0.41 0.67 2, 6 1.04 0.41 2, 9 1.01 0.40 Crop × Mulch 2, 18 0.40 0.67 2, 18 0.09 0.91 2, 9 0.48 0.63 2, 9 0.16 0.85

First sampling in the second release, 33 DAPx Crop 1, 9 66.14 < 0.0001 1, 9 79.73 < 0.0001 ------1, 9 90.08 < 0.0001 Mulch 2, 9 0.14 0.87 2, 9 0.44 0.66 ------2, 9 0.14 0.87 Crop × Mulch 2, 9 0.06 0.95 2, 9 2.68 0.12 ------2, 9 1.80 0.22

Second sampling in the second release, 33 DAPy Crop 1, 9 50.37 < 0.0001 1, 15 4.30 0.06 ------1, 15 15.05 0.001 Mulch 2, 6 0.35 0.72 2, 15 0.42 0.67 ------2, 15 0.45 0.65 Crop × Mulch 2, 9 0.45 0.65 2, 25 0.42 0.67 ------2, 25 0.50 0.62 *Larva, protonymph and deutonymph **Adult and immatures counted altogether xEvaluation performed 10 DAR yEvaluation performed 20 DAR

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Table 5-10. Mean ± SE number of A. swirskii in different crops, regardless of mulch treatment. Year Crop Mite’s stage 2015 Adult Immature Egg Total First release, 49 DAP* Eggplant ------3.28 ± 0.98az Cucumber ------3.22 ± 0.85a squash ------1.50 ± 0.39ab Pepper ------0.67 ± 0.30ab Snap Beans ------0.61 ± 0.28ab Tomato ------0.0 ± 0.0b 2016 First release, 15 DAP* Cucumber 8.33 ± 1.01az 4.41 ± 0.87a 5.00 ± 1.07a 17.75 ± 2.48a Eggplant 7.50 ± 1.10a 3.25 ± 0.76a 2.17 ± 0.04b 12.92 ± 1.80a

First sampling in the second release, 33 DAP** Cucumber 5.08 ± 0.84bz 13.50 ± 1.37b -- 18.58 ± 2.07b Eggplant 12.08 ± 1.18a 37.08 ± 3.91a -- 49.17 ± 4.60a

Second sampling in the second release, 33 DAP** Cucumber 5.75 ± 1.81bz 15.67 ± 4.46a -- 20.08 ± 5.80b Eggplant 21.58 ± 3.47a 24.75 ± 3.40a -- 46.33 ± 5.86a zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. *Mean number of A. swirskii per five leaf sample **Mean number of A. swirskii per four leaf sample

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Table 5-11. Mean ± SE number of A. swirskii in different mulch, regardless of crop treatment. Year Mulch Mite’s stage Adult Immature Egg Total First release, 15 DAP* 2016 Silver on black 5.88 ± 0.85 4.50 ± 1.27 3.00 ± 1.20 13.38 ± 2.71 Silver on white 7.75 ± 0.86 3.13 ± 0.83 3.13 ± 0.92 14.00 ± 2.31 White on black 10.12 ± 1.61 3.88 ± 0.92 4.63 ± 1.24 18.63 ± 3. 10

First sampling in the second release, 33 DAP* Silver on black 7.88 ± 1.66 27.38 ± 5.72 -- 35.25 ± 7.08 Silver on white 8.50 ± 1.90 27.13 ± 7.25 -- 35.63 ± 8.98 White on black 9.38 ± 1.91 21.38 ± 3.39 -- 30.75 ± 5.24

Second sampling in the second release, 33 DAP* Silver on black 14.88 ± 4.68 24.50 ± 6.42 -- 39.38 ± 9.90 Silver on white 11.50 ± 3.85 18.63 ± 5.16 -- 30.13 ± 8.78 White on black 14.63 ± 5.02 17.50 ± 3.35 -- 32.13 ± 6.68

2015 First release, 49 DAP* Silver on black ------1.28 ± 0.39 Silver on white ------1.72 ± 0.85 White on black ------1.33 ± 0.46 Black on black ------1.06 ± 0.55 Black on white ------1.44 ± 0.46 No mulch ------2.44 ± 0.95 *Means within the same column are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

Table 5-12. ANOVA assessing the effects of crop and mulch on the distribution of A. swirskii in different strata of host plants. Effect Mite’s stage Adult Immature Total

2016 df F P F P F P Stratum 2, 51 54.44 < 0.0001 68 < 0.0001 77.92 < 0.0001 Mulch *Stratum 4, 51 1.94 0.12 0.43 0.78 0.33 0.85 Crop *Stratum 2, 51 8.03 0.0009 1.13 0.33 3.73 0.03 Mulch * Crop * Stratum 4, 51 0.68 0.61 1.63 0.18 1.43 0.23

2015 Stratum ------2, 48* 28.28 < 0.0001 Mulch *Stratum ------10, 48 2.81 0.008 Crop *Stratum ------2, 48 2.65 0.08 Mulch * Crop * Stratum ------10, 48 2.25 0.03

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Table 5-13. Mean ± SE number of A. swirskii in different strata of different mulches, regardless of crops. Year Mulch Stratum Mite’s stage Adult Immature Total Top 1.50 ± 0.50bz 3.13 ± 0.74b 4.63 ± 1.16b 2016 Silver on black Middle 14.88 ± 4.68a 24.50 ± 6.42a 39.38 ± 9.90a Bottom 23.13 ± 5.63a 36.25 ± 8.07a 59.38 ± 13.62a F; P 31.85; < 0.0001 27.71; < 0.0001 30.54; < 0.0001

Silver on white Top 1.75 ± 0.49b 3.88 ± 1.09c 5.63 ± 1.39c Middle 11.50 ± 3.85a 18.63 ± 5.16b 30.13 ± 8.78b Bottom 16.25 ± 4.26a 38.25 ± 5.99a 54.50 ± 9.39a F; P 17.88; < 0.0001 21.86; < 0.0001 25.26; < 0.0001

White on black Top 3.50 ± 0.66b 3.25 ± 0.82c 6.75 ± 0.88c middle 13.88 ± 5.24a 17.50 ± 3.35b 31.38 ± 6.57b Bottom 13.50 ± 2.71a 42.88 ±10.37a 56.38 ± 12.38a F; P 8.58; 0.0006 25.28; < 0.0001 22.78; < 0.0001

2015 Silver on black Top -- -- 0.0 ± 0.0b middle -- -- 0.0 ± 0.0 b Bottom -- -- 1.50 ± 1.50a F; P 10.75; 0.0001 Silver on white Top -- -- 0.33 ± 0.33a middle -- -- 0.17 ± 0.17a Bottom -- -- 0.33 ± 0.33a F; P 0.64; 0.52 White on black Top -- -- 0.0 ± 0.0a middle -- -- 0.33 ± 0.21a Bottom -- -- 0.17 ± 0.17a F; P 1.22; 0.30 Black on white Top -- -- 0.0 ± 0.0 b middle -- -- 0.0 ± 0.0 b Bottom -- -- 1.50 ± 0.43a F; P 17.17; < 0.0001 Black on black Top -- -- 0.0 ± 0.0 b middle -- -- 0.33 ± 0.21b Bottom -- -- 1.33 ± 0.76a F; P 8.50; 0.0007 No mulch Top -- -- 0.0 ± 0.0b middle -- -- 0.17 ± 0.17ab Bottom -- -- 0.67 ± 0.33a F; P 3.75; 0.03 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

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Table 5-14. Mean ± SE number of A. swirskii on different strata of cucumber and eggplant, regardless of mulch treatments, 2016. Crop Stratum Mite’s stage Adult Immature Total Top 1.92 ± 0.61cz 3.25 ± 0.77c 5.17 ± 0.99c Cucumber Middle 5.25 ± 1.85b 15.67 ± 4.46b 20.92 ± 5.65b Bottom 11.0 ± 2.28a 36.17 ± 8.0a 47.17 ± 9.82 a F; P 14.83; < 0.0001 29.37; < 0.0001 29.36; < 0.0001

Top 2.58 ± 0.38b 3.58 ± 0.67c 6.17 ± 0.9b Eggplant Middle 21.58 ± 3.47a 2 4.75 ± 3.40b 46.33 ± 5.86a Bottom 24.25 ± 3.75a 42.08 ± 4.92a 66.33 ± 8.30a F; P 47.64; < 0.0001 39.76; < 0.0001 52.29; < 0.0001 zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test. For each crop, df = 2, 51

Table 5-15. Mean ± SE number of A. swirskii on different strata, regardless of crops and mulches, 2016. Stratum Mite’s stage Adult Immature Total Top 2.25 ± 0.36cz 3.42 ± 0.50c 5.66 ± 0.67c Middle 13.42 ± 2.57b 20.21 ± 2.90b 33.63 ± 4.78b Bottom 17.63 ± 2.55a 39.13 ± 4.64a 56.75 ± 6.60a zMeans within the same column followed by the same letter are not significantly different at P ≤ 0.05 according to Tukey’s HSD test.

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CHAPTER 6 SUMMARY AND CONCLUSIONS

Melon thrips, Thrips palmi Karny is a serious pest of nearly all vegetable crops and ornamental plants. This pest invaded Miami-Dade County, FL., USA in 1990. Adult and larval feeding on the cell contents of its host plants often results in bronzing of leaves, stunting of whole plants, scarring and distortion of the fruit, resulting in reduced marketable yields. Growers use different classes of insecticides as a principal tool to manage this pest. However, repetitive applications of the same chemicals resulted in reduced susceptibility and inadequate control of melon thrips. Therefore, adoption of a sustainable Integrated Pest Management (IPM) strategy may be an alternative approach to manage this economic pest. Plastic mulches are considered as an important component of an IPM technique. This study is the first attempt to test the effectiveness of different colored (white on black, black on white, and black on black) and two

UV relflective plastic mulch treatments in managing melon thrips on six field grown vegetable crops (eggplant, cucumber, squash, snap beans, Jalapeno pepper, and tomato). In all vegetable crops, significant reduction in the density of melon thrips was observed in the reflective plastic mulch treatments compared with the other non-UV reflective mulch and no mulch control treatments. The numbers of melon thrips were greatest in the white on black plastic mulch and in the control treatment. Black plastic mulches showed intermediate efficacy in reducing the number of melon thrips.

Knowledge on the population dynamics of a target pest species on the host crops is an integral part of a pest management strategy. This study showed that eggplant was the most preferable host for T. palmi followed by cucumber, snap beans, squash and jalapeno pepper with tomato being the least preferable host. In the present study, population density of melon thrips

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started to increase from 28 days after planting in each crop and mulch treatment from 28 days after planting.

Appropriate, timely and cost-effective sampling is an essential component in developing an effective IPM program. Information on the relative abundance of a pest at different locations on a host plant should be clearly assessed to develop an effective plan for sampling. Therefore, an effort was made to investigate the within-plant distributions of melon thrips in different strata of six vegetable crops grown over above-mentioned mulch treatments, based on leaf samples.

There were differences in the stratum preference by melon thrips adults and larve in different crops. Broadly, in the early and mid-season, significantly the highest numbers of melon thrips were recorded from the middle stratum followed by the bottom and top strata. However, in the late season when crop leaves in the middle and bottom strata senesced, adults were more abundant on the top stratum than the middle stratum with bottom stratum being the least number of adults. In the early season, the numbers of thrips in all the strata of metalized mulch treatments were lower compared with the other mulch and no mulch treatments. However, efficacy of metalized reflective mulches was reduced when grownup plants canopy shaded the mulched area entirely.

It is also important to explore if planting vegetable crops on reflective mulches provide better growth and yields than the commonly used plastic mulches. Accordingly, growth and yield response of six vegetable crops to different mulch treatments were studied. Except for tomato, vegetative growth based on height and width and dry biomass of roots and shoots, and yields were higher in the plastic mulch treatments than in the no mulch control treatment. Among mulches, higher plant growth attributes and yields were observed in the reflective mulches.

Compared with other plastic mulches earlier fruiting also occurred in reflective mulches.

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Combined efficacy of Amblyseius swirskii Athias-Henriot and different plastic mulch treatments for managing melon thrips in field grown vegetable crops were also assessed. Study results demonstrated that A. swirskii could not suppress melon thrips effectively when thrips population was high. However, preventive release of A. swirskii was effective in controlling low population abundance of melon thrips. There were no significant differences in the number of A. swirskii among different mulch treatments which indicates that A. swirskii mite could be integrated with UV-relfective mulch in melon thrips management program. The number of A. swirskii were higher on the bottom and middle strata than the top stratum of host plants. The number of A. swirskii in different strata were positively correlated with the number of melon thrips larvae.

Results of this study demonstrated that metalized UV reflective mulch was effective in suppressing melon thrips infestation. Within-plant distribution study results will increase the understanding of timing and occurrence of populations of melon thrips adults and larvae in the various plant strata on six commonly grown vegetable crops. Therefore, information from this study should provide essential guideline to the growers and farm managers to conduct timely, reliable and effective sampling programs to develop a successful integrated pest management program.

This study results alo indicate potential of reflective mulch to increase growth and yield of vegetable crops. However, further study is needed to explore mechanisms behind the increase growth and yield of vegetable crops grown on plastic mulches.

Overall, this research results suggest that reflective plastic mulch could be an important component of integrated management strategy for melon thrips in field grown vegetable crops.

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However, additionally, this method could be combined with early season application of biorational pesticides as well as biological control methods to increase the efficacy of an integrated pest management program. In addition, to build up a foundation of an effective integrated melon thrips management, further studies on year-round seasonal abundance, population dynamics, damage potential and interaction between melon thrips and these hosts needed to be explored. Moreover, economic analysis is needed to determine the costs and benefits of using reflective plastic mulch.

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BIOGRAPHICAL SKETCH

Mohammad A. Razzak was born in 1979 in Dhaka, Bangladesh. After graduating from senior high school, he attended Jahangirnagar University to pursue B. Sc (Hons.) degree in zoology. He enrolled in the same university and earned M. Sc. in entomology in 2003. His M. Sc thesis was on “Diversity and seasonal polymorphism of butterfly fauna in Jahangirnagar

University campus”. After completion M. Sc. he started early career as a senior biology teacher at Happy Isle international school, Dhaka, where he served three years. Later, he joined

Bangladesh Atomic Energy Commission (BAEC) as a scientific officer in 2006. In BAEC, he worked on sterile insect technique to manage sheep blowfly, Lucilia cuprina. After serving four years in BAEC, he joined Jahanginagar University as a lecturer of Zoology department in 2010.

He promoted as an assistant professor in 2013. From his university life at Jahangirnagar

University he was dreaming to pursue doctorate degree from a renowned university in the United

States. To fulfill his dream, in Fall 2014, he enrolled at the University of Florida, Department of

Entomology and Nematology on an assistantship to pursue PhD degree under the supervision of

Dr. Dakshina Seal. The majority of his time was spent at the Tropical Research and Education

Center (TREC) in Homestead, Florida, where he worked on melon thrips, a serious pest of vegetable crops. During his PhD research he concentrated himself to develop an integrated approach using cultural control technique and biological control agent. During his doctoral program, he presented his research to several entomology meetings and a field day at TREC. He wrote for and awarded two Miami-Dade Agri-council scholarships and travel grant from Florida

State Horticultural Society. He got married to Nurun Nahar in 2011and become father of a son,

Abdur Rafi. After graduation Mohammad Razzak plans to continue career as an entomologist in academia.

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