Potential Predators of Corn-Infesting Picture-Winged Flies (Diptera

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Title:
Potential Predators of Corn-Infesting Picture-Winged Flies (Diptera Ulidiidae) in Homestead, Florida: Seasonal Abundance, Distribution and Functional Response
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1 online resource (114 p.)
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english
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Kalsi,Megha
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University of Florida
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Gainesville, Fla.
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Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Entomology and Nematology
Committee Chair:
Seal, Dakshina
Committee Members:
Nuessly, Gregg S
Capinera, John L

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Subjects / Keywords:
abundance -- biocontrol -- chaetopsis -- distribution -- diversity -- euxesta -- functional -- response -- ulidiidae
Entomology and Nematology -- Dissertations, Academic -- UF
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Entomology and Nematology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

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Abstract:
Several picture-winged flies (Diptera: Ulidiidae) are serious pest of sweet and field corn in southern Florida. They include Euxesta stigmatias Loew, Euxesta eluta Loew, Euxesta annonae Fabricius and Chaetopsis massyla Walker. Management of these pests is principally based on chemical insecticides. It has been reported that farmers frequently use insecticides (every 1 to 3 d) to control these pests. My field and laboratory research focused on finding natural predators of the ulidiid corn pests found in sweet corn produced in Homestead. All the studies were conducted in a sweet corn field at the Tropical Research and Education Center (TREC), Homestead, Florida. The study related to seasonal abundance and diversity of arthropods in corn ears was replicated during the spring, summer and fall seasons of 2010 (i.e. 3X). During each season, samples of corn ears were collected at three dates corresponding to corn ear development, i.e., silking, and blister and milk stages (R1, R2 and R3). The various arthropods found were Orius insidiosus Say (Hemiptera: Anthocoridae) (adults and nymphs), unidentified thrips (Thysanoptera: Thripidae), unidentified mites, unidentified Staphylinidae larvae (Coleoptera), adults and larvae of Chrysoperla carnea Smith (Neuroptera: Chrysopidae), and adults and larvae of the sap beetles Lobiopa insularis (Castelnau) and Carpophilus lugubris Murray (Coleoptera: Nitudilidae). Orius insidiosus was the most abundant arthropod during the R1 stage and was found during all seasons. The unidentified staphylinid species were found only during the summer with greater numbers during the R3 stage. The eggs and larvae of Ulidiidae corn pests were most abundant during the summer and least abundant during the spring season 2010. In the laboratory studies, two arthropods fed on ulidiid corn pests. All five nymphal and the adult stage of O. insidiosus fed on eggs and larvae of ulidiids (E. stigmatias, E. eluta, and E. annonae). Larval staphylinids also fed voraciously on eggs and larvae of the above-mentioned ulidiids. The distribution patterns of O. insidiosus nymphs and adults and staphylinid larvae in sweet corn ears were studied along with the distribution of corn-infesting ulidiid eggs and larvae. Both ulidiid eggs and larvae in corn ears showed an aggregated pattern of distribution during the three developmental ear stages throughout the study. The distribution pattern of O. insidiosus was aggregated at most sampling dates, except during the R3 in spring and fall 2010 when it was randomly distributed. The distribution pattern of staphylinid larvae was aggregated during summer (2010) at the R3 stage. Additional studies were conducted to check the efficacy of O. insidiosus as a predator. Orius insidiosus displayed a type III functional response to laboratory-reared eggs of E. stigmatias, E. eluta, and E. annonae. The handling time and attack constant was nearly similar for the eggs of different Euxesta spp. that were tested. In the experimental fields at TREC, Homestead, Zelus longipes Fabricius (Hemiptera: Reduviidae) was observed feeding on the adults of Ulidiidae corn pests. Within-plant, within-field and temporal distribution studies of Z. longipes and Ulidiidae adults were conducted at three different time intervals (0900-1000 h EST, 1300- 1400 h EST and 1700-1800 h EST) and at three developmental ages of ears (i.e., silking/R1, blister/R2, and milk/R3 stage). The plants were divided into four strata: basal leaves (i.e., leaves present on lower three collar bands of stem), middle leaves (i.e., leaves above the lower three collar bands and those surrounding the ear), fruit and top/tassels (i.e., leaves and tassels above the ear). The abundance of both Z. longipes and corn-infesting Ulidiidae adults varied depending on time interval, ear age, and within-corn plant location. During the R3 stage, Z. longipes and corn-infesting Ulidiidae adults occurred throughout the corn plant irrespective of time interval. The abundance of Z. longipes and corn-infesting Ulidiidae peaked on fruit and tassels at 1300-1400 and 1700-1800 h EST, respectively. The population abundance of corn-infesting Ulidiidae increased during the R2 stage with peak abundance on leaves (basal and middle), fruits, and top/tassels at 0900-1000, 1300-1400 and 1700-1800 h EST, respectively. The distribution pattern of Z. longipes was similar to ulidiid adults. Population abundance of both prey and predator at R3 stage was high on basal leaves at 0900-1000 h ES, and moved to corn ears and tassels as time intervals progressed (i.e., at 1700-1800 h EST). It was observed that at the time of silking (R1 stage), both corn-infesting Ulidiidae adults and Z. longipes showed mostly aggregated and random distribution, respectively, at different time intervals. At R2 and R3 stages, both prey and predator exhibited aggregated distributions irrespective of time interval. A functional response experiment to test the efficacy of lab-reared Z. longipes (adult male and females) as a predator to lab-reared Euxesta spp. (E. stigmatias, E. eluta and E. annonae) adults was conducted in laboratory. The adults (of each fly species) in batches of 2, 4, 6, 8 and 10 were placed with one predator (either male or female) in a feeding arena (circular plastic box) for 24 h. Both male and female Z. longipes showed a type II functional response to adults of all three ulidiid species tested. Handling time was longer for males than females, but the attack rate constant was determined to be nearly the same for both male and female Z. longipes.
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In the series University of Florida Digital Collections.
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Includes vita.
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Statement of Responsibility:
by Megha Kalsi.
Thesis:
Thesis (M.S.)--University of Florida, 2011.
Local:
Adviser: Seal, Dakshina.
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RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2012-08-31

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1 POTENTIAL PREDATORS OF CORN INFESTING PICTURE WINGED FLIES (DIPTERA: ULIDIIDAE) IN HOMESTEAD FLORIDA : SEASONAL ABUNDANCE, DISTRIBUTION AND FU NC TIONAL RESPONSE By MEGHA KALSI A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2011

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2 2011 Megha Kalsi

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3 To my f ather the biggest inspiration in my life and my mother for her unconditional love

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4 AC KNOWLEDGMENTS I would like to convey my sincere thank to my advisor Dr. Dakshina R. Seal for his project. I want to thank my committee members Dr. J. L. Capinera and Dr. G. Nue ssly for their guidance and valuable suggestions. My writing was greatly supported by all of them because of their advice and criticism throughout my thesis writing. Our administrator Debbie Hall kept me on track if not on schedule, a special thanks to h er. My thanks to all the lab personnel Ms. Catherine Sabines, Mr. Charlie, and Mr. Jacinto, for helping me with the entire field project. My parents have been a continuous source of my strength and I am indebted to them. I am grateful to my siblings Rhy thm and Karam who helped me to stay determined towards my goals. Special thanks to all my friends Vivek, Garima, Nicki, Xiodan, Alina and Jian for their support. And above all, I thank the almighty for giving me this opportunity.

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5 TABLE OF CONTENTS P ag e ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ..................... 9 CHAPTER 1 LITERATURE REVIEW ................................ ................................ .......................... 13 Introduction ................................ ................................ ................................ ............. 13 Taxonomy ................................ ................................ ................................ ............... 14 Family: Ulidiidae ................................ ................................ ............................... 14 Subfamily: Ulidiinae ................................ ................................ .......................... 15 Genus Euxesta ................................ ................................ ................................ 15 Genus Chaetopsis Loew ................................ ................................ .................. 16 Host Plant Range ................................ ................................ ................................ .... 17 Life Cycle ................................ ................................ ................................ ................ 19 Management of Corn Infestin g Ulidiidae Flies ................................ ........................ 19 Chemical Control ................................ ................................ .............................. 19 Host Plant Resistance ................................ ................................ ...................... 20 Biological Control ................................ ................................ ............................. 21 Research Objectives: ................................ ................................ .............................. 23 2 SEASONAL ABUNDANCE AND DISTRIBUTION OF THE ARTHROPODS FOUND IN CORN EARS WITH IDENTIFICATION OF THEIR PREDATORY STATUS ................................ ................................ ................................ .................. 27 Materials and Methods ................................ ................................ ............................ 30 Seasonal Abundance and Diversity of Arthropods ................................ ........... 32 Spatial Distribution of Predators and Corn Infesting Ulidiids ............................ 33 Laboratory Evaluation of Arthropod Species for Predatory Status ................... 35 Functional Response of O. insidiosus to Eggs of Euxesta s pecies .................. 38 Results ................................ ................................ ................................ .................... 40 Seasonal Abundance and Diversity of Arthropods ................................ ........... 40 Spatial Distribution of Predators and Corn Infesting Ulidiids ............................ 43 Laborator y Evaluation of Arthropod Species for Predatory Status ................... 45 Functional Response of O. insidiosus to Eggs of Euxesta species .................. 46 Dis cussion ................................ ................................ ................................ .............. 46

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6 3 DISTRIBUTION A ND FUNCTIONAL RESPONE OF ZELUS LONGIPES (L.) (HEMIPTERA: REDUVIIDAE) TO CORN INFESTING ULIDIIDAE FLIES (DIPTERA: ULIDIIDAE) ................................ ................................ .......................... 67 Materials and Methods ................................ ................................ ............................ 70 Within Plant Distribution ................................ ................................ ................... 71 Within Field and Temporal Distribution ................................ ............................ 72 Functional R esponse of Zelus longipes to Euxesta stigmatias, Euxesta eluta and Euxesta annonae ................................ ................................ ........... 73 Results ................................ ................................ ................................ .................... 77 Within Plant Distribution ................................ ................................ ................... 77 Within Field and Temporal Distribution ................................ ............................ 79 Functional R esponse of Zelus longipes to Euxesta stigmatias, Euxesta eluta and Euxesta annonae ................................ ................................ ........... 81 Discussion ................................ ................................ ................................ .............. 82 4 CONCLUSIONS ................................ ................................ ................................ ..... 96 LIST OF REFERENCES ................................ ................................ ............................. 100 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 114

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7 LIST OF TABLES Table P age 1 1 Various host pla nts of corn infesting Ulidiidae ................................ .................... 18 2 1 Planting and sampling dates for the sweet corn experiments ............................. 53 2 2 Arthropods found in sweet co rn during di fferent season 2010 ............................ 53 2 3 Mean number ( SE) of Euxesta spp. (eggs, larvae and adults) ea ten by generalist predators ................................ ................................ ............................ 54 2 4 D istribution of predators and pests in sweet corn ears during spring 2010 ....... 55 2 5 D istribution of predators and pests in sweet corn ears during summer 2010 .... 56 2 6 D istributi ons of predators and pests in sweet corn ears during fall 2010 ........... 57 2 7 Maximum likelihood estimates from logistic regression ................................ ...... 58 2 8 Type III functional res ponse of O. insidiosus to eggs of Euxesta sp ecies .......... 58 3 1 D istribution o f corn infesting Ulidiidae sampled in a cornfield at R1 stage ......... 85 3 2 D istributi on of corn infesting Ulidiidae sampled in a corn field at R2 s tage ........ 86 3 3 D istr ibution of corn infesting Ulidiidae sampled in corn field at R3 stage ........... 87 3 4 D i stribution of Z. longipes adults sampled in a corn field at R1 stage ................. 88 3 5 D is tribution of Z. longipes adults sampled in a corn field at R2 stage ................. 89 3 6 D ist ribution of Z. longipes adults sampled in a corn field during R3 stage .......... 90 3 7 Parameters (means S.E) estimated by random predator equation .................. 90

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8 LIST OF FIGURES Figure P age 1 1 Major sweet corn prod ucing re gions in Florida (Mossler 2008) .......................... 24 1 2 Euxesta stigmatias (Loew) eggs in corn silk ................................ ....................... 24 1 3 Third larval instar of Euxesta stigmatias (Loew) ................................ ................. 25 1 4 Different stages of Euxesta stigmatias pupal development ................................ 25 1 5 Damaged sweet corn ear due to severe Ulidiidae larval feeding ........................ 26 2 1 The expe rimental set u p for functional response study ................................ ...... 59 2 2 Mean number of potential predators of ulidiid corn pest found in corn ears during spring 2010 ................................ ................................ .............................. 60 2 3 Mean number of potential predators of ulidiid corn pest found in corn ears during summer 2010 ................................ ................................ ........................... 61 2 4 Mean number of potential predators of ulidiid corn pest foun d in corn ears during fall 2010 ................................ ................................ ................................ ... 62 2 5 Mean seasonal abundance of O. insidiosus durin g spring, summer, and fall 2010 ................................ ................................ ................................ ................... 63 2 6 Mean seasonal abundance of Ulidiidae eggs and larvae during spring, summer, and fall 2010 ................................ ................................ ........................ 63 2 7 The first instar nymph of O. insidiosus feeding on a Euxesta stigmatias ............ 64 2 8 Adult O. insidiosus feeding on a third instar larva of E uxesta stigmatias ............ 64 2 9 Staphylinid larva feeding on Euxesta stigmatias eggs ................................ ........ 65 2 11 Type III functional response of Orius insidiosus to eggs of Euxesta species ...... 66 3 1 Zelus longipes female feeding on Euxesta stigmatias in sweet corn field .......... 91 3 2 Mean number of Z. longipes and corn infesting Ulidiidae adults per time interval in various plant parts ................................ ................................ .............. 93 3 3 Type II functional response of male Zelus longipes to Euxesta species ............. 94 3 4 Adult male, Z. longipes feeding on Euxesta annonae adult in lab experiment .... 95

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9 ABSTRACT OF THESIS PRESENTED TO THE GRA DUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL F ULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE POTENTIAL PREDATORS OF CORN INFESTING PICTURE WINGED FLIES (DIPTERA: ULIDIIDAE) IN HOMESTEAD FLORIDA : SEASONAL ABUNDANCE, DISTRIBUTION AND FU NC TIONAL RESPONSE By Megha Kalsi August 2011 Chair: Dakshina. R. Seal Major: Entomology and Nematology Several picture w inged flies (Diptera: Ulidiidae ) are serious pest of sweet and field corn in southern Florida. They include Euxesta stigmatias Loew Euxesta eluta Loew Euxesta annonae Fabricius and Chaetopsis massyla Walker. Management of these pests is principally bas ed on chemical insecticides It has been reported that farmers frequently use insecticides (every 1 to 3 d) to control these pests. My field and laboratory research focused on finding natural predators of the ulidiid corn pests found in sweet corn produc ed in Homestead. All the studies were conducted in a sweet corn field at the Tropical Research and Education Center (TREC), Homestead, Florida. The study related to seasonal abundance and diversity of arthropods in corn ears was replicated during the spri ng, summer and fall seasons of 2010 (i.e. 3X). During each season, samples of corn ears were collected at three dates corresponding to corn ear development, i.e., silking, and blister and milk stages (R1, R2 and R3). The various arthropods found were Ori us insidiosus Say (Hemiptera: Anthocoridae) (adults and

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10 nymphs), unidentified thrips (Thysanoptera: Thripidae), unidentified mites, unidentified Staphylinidae larvae (Coleoptera), adults and larvae of Chrysoperla carnea Smith (Neuroptera: Chrysopidae), and adults and larvae of the sap beetles Lobiopa insularis (Castelnau) and Carpophilus lugubris Murray (Coleoptera: Nitudilidae) Orius insidiosus was the most abundant arthropod during the R1 stage and was found during all seasons. The unidentified staphyl inid species were found only during the summer with greater numbers during the R3 stage. The eggs and larvae of Ulidiidae corn pests were most abundant during the summer and least abundant during the spring season 2010. In the laboratory studies, two art hropods fed on ulidiid corn pests. All five nymphal and the adult s tage of O. insidiosus fed on eggs and larvae of u lidiids ( E. stigmatias E. eluta and E. annonae ). Larval s taphylinid s also fed voraciously on eggs and larvae of the above mentioned u lid iids. The distribution patterns of O. insidiosus nymphs and adults and staphylinid larvae in sweet corn ears were studied along with the distribution of corn infesting ulidiid eggs and larvae. Both ulidiid eggs and larvae in corn ears showed an aggregated pattern of distribution during the three developmental ear stages throughout the study. The distribution pattern of O insidiosus was aggregated at most sampling dates, except during the R3 in spring and fall 2010 when it was randomly distributed. The d istribution pattern of staphylinid larvae was aggregated during summer (2010) at the R3 stage. Additional studies were conducted to check the efficacy of O. insi dios us as a predator. Orius insidiosus displayed a type III functional response to laboratory reared eggs of E.

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11 stigmatias E. eluta and E. annona e. The handling time and attack constant was nearly similar for the eggs of different Euxesta spp. that were tested. In the experimental fields at TREC, Homestead, Zelus longipes Fabricius (Hemiptera: Reduviidae) was observed feeding on the adults of Ulidiidae corn pests. Within plant, within field and temporal distribution studies of Z. longipes and Ulidiidae adults were conducted at three different time intervals (0900 1000 h EST, 1300 1400 h EST an d 1700 1800 h EST) and at three developmental ages of ears (i.e., silking/R1, blister/R2, and milk/R3 stage). The plants were divided into four strata: basal leaves (i.e., leaves present on lower three collar bands of stem), middle leaves (i.e., leaves ab ove the lower three collar bands and those surrounding the ear), fruit and top/tassels (i.e., leaves and tassels above the ear). The abundance of both Z. longipes and corn infesting Ulidiidae adults varied depending on time interval, ear age, and within c orn plant location. During the R3 stage, Z. longipes and corn infesting Ulidiidae adults occurred throughout the corn plant irrespective of time interval. The abundance of Z. longipes and corn infesting Ulidiidae peaked on fruit and tassels at 1300 1400 and 1700 1800 h EST, respectively. The population abundance of corn infesting Ulidiidae increased during the R2 stage with peak abundance on leaves (basal and middle), fruits, and top/tassels at 0900 1000, 1300 1400 and 1700 1800 h EST, respectively. The distribution pattern of Z longipes was similar to ulidiid adults. Population abundance of both prey and predator at R3 stage was high on basal leaves at 0900 1000 h ES, and moved to corn ears and tassels as time intervals progressed (i.e., at 1700 1800 h EST). It was observed that a t the time of silking (R1 stage), both corn

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12 infesting Ulidiidae adults and Z longipes showed mostly aggregated and random distribution respectively, at different time intervals. At R2 and R3 stages, both prey and predator exhibited aggregated distribution s irrespective of time interval A functional response experiment to test the efficacy of lab reared Z. longipes (adult male and females) as a predator to lab reared Euxesta spp. ( E stigmatias E eluta and E annonae ) ad ults was conducted in laboratory. The adults (of each fly species) in batches of 2, 4, 6, 8 and 10 were placed with one predator (either male or female) in a feeding arena (circular plastic box) for 24 h. Both male and female Z. longipes showed a t ype II functional response to adults of all three ulidiid species tested Handling time was longer for males than female s, but the attack rate constant was determined to be nearly the same for both male and female Z. longipes

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13 CHAPTER 1 LITERATURE REVIEW Intro ductio n Sweet corn ( Zea mays var. rugosa Bonaf.) originated in Pennsylvania in the 1700 s as a result of a genetic mutation in the gene pool of field corn (Hansen 2011) Sweet corn was introduced there commercially in 1779 (Hansen 2011) The United State s has been the largest producer of sweet corn in the world since the 1960 s (ERS 2008) By 2004, Mexico had become the second largest producer (AgMRC 2010). In Unites states ( 2009 ) the value of fresh market sweet corn was $ 835.3 million, and for proces sed corn, it was $335.6 million (Hansen 2011). In the United States, Florida dominates the fresh market sweet corn production and contributes about 20 percent of the national sweet corn production. Half the sweet corn produced in Florida comes from the E verglades production area in Palm Beach County. In addition, a quarter of the state corn production occurs in Miami Dade, Collier, and Hendry counties combined (Mossler 2008) (Fig.1 1). In 2006, fresh sweet corn was produced on 10 643 ha in Florida with a total volume of 212 million kg valued at $117 million. Other major sweet corn producing states in the United States are California, Georgia, and New York (AgMRC 2010). Fresh corn is also important for export and has a high sale value for daily spot mar kets. Although production and revenue generated by fresh corn production depends highly on supply and demand in the marketplace, factors like cosmetic value are also very important. The warm, humid climate of Florida provides a favorable environment for g rowth and proliferation of pest populations. Many species of pest insects attack sweet corn,

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14 causing considerable economic losses (Nuessly and Webb 2010) The most common sweet corn pest species in Florida are: fall armyworm, Spodoptera fugiperda (Smith) (Lepidoptera: Noctuidae), corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae), and picture win ged flies, (Diptera: Ulidiidae) (Nuessly and Webb 2010). Four Uli diidae species damage corn in Florida: Euxesta annonae (Fabricius 1794), Euxesta eluta (Loew 1868), Euxesta stigmatias (Loew 1868), and Chaetopsis massyla (Walker 1849) (Goyal et al. 2011) Taxonomy winge ir diverse wing patterns ( Kameneva and Korneyev 2006 ) Ulidiidae, formerly known as Otitidae ( Kameneva and Korneyev 2006 Thompson 2006 Goyal et al. 2010), is one of the least studied families with knowledge on basic biology and be havior limited to a few species of e conomic importance (Harper 1962, Allen a nd Foote 1967, 1975, Frias 1978, Yoon et al. 1983, Seal and Jansson 1993, Seal et al. 1995, Nuessly and Hentz 2004). The Ulidiid ae flies belong to the superfamily Tephritoidea (McA lpine 1989 Korne yev 2000, Brunel and Rull 2010). Ulidiidae is a small family of about 800 species (Daz Feischer et al. 2000 Brunel and Rull 2010) including saprophytic and phytophagous insects (Allen and Foote 1967 Korneyev 2000). Family: Ulidiidae T he Ulidiidae are small to medium sized (2.5 11.0 mm), diversely colored acalyptrate flies ( Kameneva and Korneyev 2006 metallic, partly yellow, and have black and grey microtomentose pubescence. They

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15 have variable hea d shapes with setulosed or bare arista. Ocelli are present with parallel or divergent postocellar setae. Wings have variable patterns, and are rarely clear or uniform in color ( ) Wings may have dark bands, dark tips, or maculation with a s pecific type of venation. The costa is mostly complete or with a humeral break. The subcosta is complete, and the R1 vein is bare or setulose. The phallus is long and coiled. Females have a well developed ovipositor with oviscape. Subfamily: Ulidiinae The family Ulidiidae includes two subfamilies Otitinae and Ulidiinae (Hennig 1939 Steyskal 1961). The subfamily Otitinae was considered a separate family by at least one author (Greve 1998). The Otitinae and Ulidiinae can be differentiated based on the aedeagus and wing vein R1. In Ulidinae, the R1 is bare (except in Neoeuxesta and Pareuxesta ), whereas in Otitinae, it is setulose. Ulidinae males have a bare aedeagus that may have a specialized tip, but Otitinae males have a bristly or hairy aedeagus w ith a simple tip (Steyskal 1961). Euxesta and Chaetopsis are two important genera belonging to the subfamily Ulidinae. Genus Euxesta The adult flies have metallic body coloration (Steyskal 1952). The head of the adult flies with v ery fine, short, prescu tellar bristles. There are three important Euxesta species that are known to be economic pests of sweet corn in southern Florida (Goyal et al. 2011). Euxesta stigmatias : The lunule (e.g., area on head between the antennae) is velvety black (Wulp 1903) The eyes are reddish brown, and wings darkly banded (Nuessly and Capinera 2010 Seal et al. 1995). The first three wing bands are complete

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16 and the fourth band is incomplete. The first band is located near the wing base and There is a clear portion between the third and fourth as it approaches the rear wing margin (Nuessly and Capinera 20 10 ). Males (3.8 mm) are shorter than females with short and rounded abdomens, whereas females (4.2 mm) have a trapezoidally shaped abdomen with a pointed end. The legs are black in color. The u pper apex of the antennal flagellomere is round (Steysakl 1952 Goyal et al. 2010). Euxesta eluta : The lunule is opaque black ( Curran 1935 Nuessly and Webb 2010) The f ront of the head is a dull reddish color The fore wings have four dark bands that continue completely from the front to the rear margins A clear area between the third and fourth bands of the marginal cell tha t continues to the front wing margin varies in size between individuals. Euxesta annonae : The head is reddish and somewhat metallic. The lunule is orange to silver and distinguishes this species from E. stigmatias and E. eluta The first wing band cove rs almost 33% of the basal part of wing cell `c`. The clear portion between the third and fourth band does not continue through the `r1` cell and remains darker near the rear wing margin (Curran 1935, Nuessly and Webb 2010). Genus Chaetopsis Loew The head is broad and the upper apex of the third antennal segment is pointed or angulated rather than rounded as in the Euxesta spp (Steyskal 1952). A few pairs of cruciate bristles are present on the medifrons. The apical anal cell of the wing has a prolonged angle.

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17 Chaetopsis massyla : The length of the body is 6.4 7.6 mm. The thorax is greenish grey with a dark green to black abdomen (Nuessly and Webb 2010). In contrast to the Euxesta spp. described above, t he legs of C. massyla are yellow T hree dark ban ds are found on the fore wings with a transparent region between all three bands The non pigmented area between the first and second dark bands is wider than between the last two dark bands. The frontal vita on the head is bare and lacks setae. The ovip ositor is broad, depressed, and thin and laminar apically (Nuessly and Webb 2010 Goyal et al. 2010). Host Plant Range Some Euxesta species, such as E. stigmatias ( Seal and Jansson 1989 Pacheo 1985 Cortez 2008), E. eluta, and E. annonae (Frias 1978 Goy al et al. 2010 ) feed on corn ears Allen and Foot (1992) reported C. massyla as a saprophagous species inhabiting marine and fresh water environments. It was considered to be secondary pest until recently when Goyal et al. (2010) reported it to be a dire ct pest of sweet corn. The known host range of the four ulidiid species that attack corn in Florida has been reported by numerous authors ( Ta ble 1 1 ) and includes many plant species other than Z. may s.

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18 Table 1 1 V arious host plants of corn infesting Ul idiidae Ulidiidae fly species Host plants Euxesta stigmatias Sweet Corn ( Zea mays ), Sorghum ( Sorghum bicolor Moench), tomato ( Lycopersicon esculentum Mill.), sugarcane ( Saccharum officinarum L.), guava ( Psidium guajava L.), banana ( Musa spp.), sour orang e ( C itrus aurantium L.), atemoya ( Annona squamosa L and A cherimolia Miller), orchid ( Dendrobium spp.), and potato ( Solanum tuberosum L.) (Seal and Jansson 1989, 1996) spiny amaranth ( Amaranthus spinosus L.) avocado ( Persea americana Mill.), sorghum ( So rghum bicolor (L.) Moench), sugarcane ( Saccharum officinarum L.), bell pepper ( Capsicum annum L.) tomato ( Solanum lycopersicum L.), johnsongrass ( Sorghum halepense (L.) Pers.), habaero pepper ( Capsicum chinense Jacquin), little hogweed ( Portulaca olerac ea L.), radish ( Raphanus sativus L.), papaya ( Carica papaya L.), and cattail ( Typha latifolia L.) (Goyal 2010) Euxesta eluta Sweet corn, Spiny amaranth hass avocado, sorghum sugarcane bell pepper tomato johnsongrass habaero pepper , little hogweed , radish papaya cattail (Allen and Foote 1992, Goyal 2010 ), and loquat ( Eriobotrya japonica Thumb.) (Anonymous 20080 Euxesta annonae Pineapple (Illingworth 1929), banana ( Musa spp.) (Severin and Hartung 1912) Chaetopsis massyla Onions, Allium cepa L. (Merrill 1951), Narcissus sp. (Blanton 1938), spiny amaranth avocado, sorghum sugarcane, bell pepper, tomato , johnsongrass, habaero pepper little hogweed radish, papaya, and cattail (Goyal 2010)

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19 Life Cycle Euxesta stigmatias completes its li fe cycle in 24 27 d, and adults can live up to 116 d under ideal food and water conditions (Nuessly and Capinera 20 10 ). It can produce u p to 20 generations per year (Bailey 1940). The egg (Fig. 1 2), larval (Figs. 1 3 ) and pupal ( Fig. 1 4) periods for E st igmatias ranged from 1.4 4 d, 7.5 27 d and 5.6 9.2 d, respectively ( App 1938, Seal and Jansson 1989, Hentz and Nuessly 2004, Goyal 2010) L arvae eclose from eggs that feed s on silk, corn kernels and cob (Fig. 1 5 ). Allen and Foot (1992) reared C. massyla adults on decaying cattail stems (infested by Noctuidae larvae) at 22 to 25 C. The y further reported that C. massyla requires 33 d for development of eggs to adult stage. The egg, larval and pupal period for C. massyla ranged from 2 3 d, 11 d and 10 d, respectively (Allen and Foot 1992). G oyal (2010) studied the development of corn infesting Ulidiidae ( E. stigmatias, E. eluta, and C. massyla ) in the field during three seasons and on an artificial medium at 26.5 1 C. In filed studies the average deve lopmental period ranged from 17.3 to 33.2 d, 18.7 to 35.2 d, and 17.2 to 33.6 d for C. massyla, E. eluta, and E. stigmatias respectively. In the laboratory studies the developmental period for C. massyla, E. eluta, and E. stigmatias were 30.2 d, 21.6 d and 27.4 d, respectively. There have been no reports on developmental studies of E annonae Management o f Corn Infesting Ulidiidae F lies Chemical Control The most widely used control methods for Euxesta spp. include insecticides belonging to various clas ses. Bailey (1940) recommended using a mixture of pyrethrin and mineral oil manually injected into ears (1:5) as an insecticide against adult flies in

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20 Puerto Rico. Hayslip (1951) studied the effectiveness of parathion and suggested multiple applications of this chemical at 3 4 d intervals. Nuessly and Hentz (2004) studied the effectiveness of various insecticides (esfenvalerate, cyfluthrin, lambda cyhalothrin, chlorpyrifos, methyl parathion, methomyl, and thiodicarb) against corn infesting ulidiid throug h direct contact and dried leaf residues In the direct application study of insecticides it was found that all but thiodicarb had quick killing or sublethal affects on > 75% of the flies. In the contact leaf residue study it was observed methyl parathio n was most effective in killing in adult flies. Seal (2001) suggested ulidiid pest resurgence even after application of chemical insecticides. He reported after insecticide application, the count of ulidiid adults was 3 6 / plant. In another experiment, N uessly and Hentz (2002) observed 11% infestation by larvae after application of the best performing insecticide, cyfluthrin (Baythroid 2) (Bayer Crop Science, Kansas City, MO). In Florida ( 2006 ) 98% of sweet corn acreage was sprayed with a total of 155,3 00 pounds of insecticide. Overall, 20 percent of expenses involved in sweet corn production are for pesticide application (Mossler 2008), but the pesticides are useful only for adult fly control. In addition to the above mentioned problems b road spectrum insecticides not only kill pests but also reduce the number of natural enemies, adversely affecting the ir potential for use in integrated pest management (Duffie et al. 1998 Tillman and Mulrooney 2000 Musser et al. 2004). Host Plant R esistance In additi on to chemical control, other methods have also been exploited to control corn infesting Ulidiidae, for example, host plant resistance. Hybrid maize varieties with high maysin content, such as Zapalote Chico 2451 and Zapalote Chico sh2, have been

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21 reported to effectively resist attack by E. stigmatias (Nuessly et al. 2007). Daly and Buntin (2005) found fewer E uxesta spp. larvae and adults on transgenic corn varieties expressing Cry1Ab toxin from Bacillus thuringiensis var kurstaki (Bt) as compared to other standard non transgenic varieties. It was reported that decreased infestation of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) resulted in reduced attraction of corn infesting ulidiids (as these flies are known to their lay eggs on corn area where da mage is caused by the lepidopteran pests) Biological Control Given the difficulties with management strategies such as insecticidal control, host plant resistance, and cultural control, its important to explore the other management techniques such as biolo gical control using natural enemy as a predator of the pest flies An improved understanding of natural enemy population dynamics and its role in pest control are required to devise less invasive methods and to potentially integrate them at a commercial l evel, thus providing a cost effective option to the producer (Musser et al. 2004). The temporal and spatial distributions of predators in response to abiotic and biotic factors require effective sampling to estimate predator populations (Ewert and Chiang 1966 Kawai 1976 Coll and Bottrell 1991 Cottrell and Yeargan 1999, Nault and Kennedy 2000 Musser et al. 2004). Hence, studying predator populations combined with accurate sampling methods will help determine which natural enemy species and the sizes of their populations are required to control the pests. The insidious flower bug, Orius insidiosus Say (Hemiptera: Anthocoridae), can be common in corn ( Zea mays L.) particularly during silking and pollination (Corey 1994, Corey et al. 1998). Orius spp. ar e polyphagous predators that feed partly or solely on

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22 corn plant material like pollen (Kiman and Yeargan 1985 Sigsgaard and Esbjerg 1997) They also feed on arthropod pests such as aphids (Hemiptera: Aphididae) (Barber 1936 Dicke and Jarvis 1962 Bush e t al. 1993 Fox et al. 2004 Rutledge et al. 2004 Lundgren and Fergen 2006), thrips (Thysanoptera: Thripidae) (van den Meiracker and Ramakers 1991 Sabelis and Van Rijn 1997 Funderburk et al. 2000 Ramachandran et al. 2001 Baez et al. 2004) The nymphs and adults of Orius spp. feed on eggs and larvae of eggs and larvae of Lepidoptera (Barber 1936 Bush et al. 1992) including corn pests, such as corn earworm, Helicoverpa zea (Boddie) (Barber 1936 Isenhour and Marston 1981 Isenhour and Yeargan 1981 Coll and Bortell 1991 Bush et al. 1993), and the European corn borer, Ostrinia nubilalis Hubner (Lepidotera: Crambidae) ( Isenhour and Marston 1981 Isenhour and Yeargan 1981 Coll and Bortell 1991 Corey et al. 1998). Recently, Baez et al. (2010) found diffe rent Orius spp. feeding on different life stages of Euxesta spp. Milkweed assassin bug, Zelus longipes (Hemiptera: Reduviidae) is a generalist predator commonly found in corn fields in Florida (Nuessly et al. 2010). It has been reported to feed on the cor n pest S fugiperda (Cogni et al 2000) Unigarro (1958) suggested that Z. longipes could be a potential biological control agent. Other predators have been observed to feed on eggs of corn infesting ulidiids Van Zwaluwenburg (1917) observed a capsid b ug feeding on E stigmatias eggs. Seal and Jansson (1989) reported that earwigs (Dermaptera: Forficulidae, Labiidae), and mites preyed on eggs of Euxesta spp In Mexico, wasps, Spalangia spp. ( Hymenoptera: Pteromalidae ) and Eurytomid (Hymenoptera: Euryto midae) have been

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23 reported to parasitize Euxesta spp. pupae (Baez et al. 2010). To develop a biological control strategy for corn infesting Ulidiidae, it is important to know which natural enemies exist in the corn fields A better understanding of the di stribution of these prey species and their predators will help in developing control measures for the corn pests. Research Objectives: T o determine the abundance and diversity of arthropods in corn ears produced in sweet corn fields. To identify the arth ropods found in ears and to determine their suitability as predators to egg, larvae, and adults of Euxesta stigmatias Euxesta eluta and Euxesta annonae To determine spatial distribution of the predators found in ears relative to the spatial distribution of corn infesting ulidiid eggs and larvae. To determine functional responses of predators observed feeding on different life stages of ulidiid ( E. stigmatias E. eluta and E. annonae ) in the laboratory. To find the within plant and within field distribut ion of ulidiid and their predator Zelus longipes in sweet corn field.

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24 Figur e 1 1 Major sweet corn producing regions in Florida ( Mossler 2008 ). Figure 1 2. Euxesta stigmatias (Loew) eggs in corn silk.

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25 Figure 1 3 Third larval instar of Euxesta st igmatias (Loew). Figure 1 4 Different stages of Euxesta stigmatias pupal development showing change in color from yellow to dark brown.

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26 Figure 1 5 Damaged sweet corn ear due to severe Ulidiidae larval feeding.

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27 CHAPTER 2 SEASONAL ABUNDANCE A ND DIS TRIBUTION OF THE ART HROPODS FOUND IN CORN EARS WITH IDENT IFICATION OF THEIR P REDATORY STATUS Several species of picture winged flies (Diptera: Ulidiidae ) have become serious pests of sweet corn in United States (Van Zwaluwenberg 1917, Barber 1939, Hayslip 1951, Seal and Jansson 1989, Nuessly and Hentz 2004, Goyal et al. 2010). By 2011, four Ulidiidae fly species in the genera Euxesta and Chaetopsis were reported to infest sweet corn in Florida. These include Euxesta stigmatias (Loew), Euxesta Eluta (Loew) Euxesta annonae (Fabricius) and Chaetopsis massyla (Walker) (Diptera: Ulidiidae) (Goyal et al. 2010). Th e corn infesting ulidiid pest de posits their eggs among silk s trands in the silk canal Upon emergence, first instar larvae feed on corn silk and pr ogress down the silk towards the kernels The larval infestation disrupts pollination by severing the corn silk (Baily 1940). Larvae may enter kernels through the soft R1 and R2 stage pericarp Larvae that make it to the ears may also feed on the cob (A pp 1938, Seal and Jansson 1989 Scully et al. 2007 ). S weet corn ears become unmarketable if the larval infestation damages corn kernels. Since the 1960s, the United States has ranked highest in the world in sweet corn production (Hansen 2011). Sweet cor n is marketed at three levels: fresh, processed, and canned food. Fresh corn is subject to high variability of supply and demand within a daily spot market, unlike processed and canned corn, which is produced on a more stable contract basis (Hansen 2011). I n 2009, fresh corn was valued at $835.8 million whereas revenue from processed corn (frozen and canned) was $335.6 million (USDA 2010) Florida is a leading producer of fresh sweet corn in the United States (Mossler 2008). According to Economic Resear ch Service (2010), Florida produced 67% of the

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28 total national sweet corn from 2007 to 2009. Hence, pest management of Ulidiid flies infesting sweet corn is very important. Chemical insecticides are currently the only effective management technique to con trol these flies. S weet corn fields in the R1 through R3 stages are often sprayed daily with insecticides (Gaurav 2010) that are effective at killing adult flie s while other life stages remain protected the ears (eggs and larvae ) or soil (pupae) (Nuessly and Capinera 2010). The sweet corn variety ha s shown reduced damage to E. stigmatias indirectly ( Nuessly et al. 2007 ) This was supported by decreased damage caused by Spodoptera f r ugiperda Smith (Lepido ptera: Noctuidae) to these corn varieties as the damage caused by this lepidopteron pest provides ovipositional sites for ulidiids. But currently this variety is not used in management of the corn infesting ulidiids. As these corn varieties shows a reduce d damaged to the lepidopteron corn pest, it will require reduced usage of insecticides supporting the natural enemy populations occurring in corn field. It would be very beneficial to find natural predator s to control corn infesting Ulidiidae. Accordin g to Stern (1981), two important pest control techniques involve manipulati ng the agroecosystem to make it less favorable for the pests or more favorable for their natural enemies. Considering the latter resort, a first step in managing corn infesting Uli diidae involves examining the arthropod composition of corn ears including predators that specifically prey on ulidiid eggs and larvae I n the n ortheastern United States, primary predators of sweet corn pests are Coleomegilla maculata (DeGeer) (Coleopte ra: Coccinellidae), Harmonia axyridis

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29 (Pallas) (Coleoptera: Coccinellidae) and Orius insidiosus (Say) (Hemiptera: Anthocoridae) (Andow and Risch 1985, Coll and Bottrell 1992, Coderre et al. 1995, Wheeler and Stoops 1996, Hoffmann et al. 1997, Musser et al. 2004). Albajes et al. (2003) studied predator composition and abundance in corn field s in Lleida, northeastern Spain using visual sampling and pitfall trapping. Carabidae (Coleoptera) Staphylinidae (Coleoptera) Coccinellidae, Heteroptera, and Aran e ae were abundant in visual samples of the corn foliage while Araneae, Opilionidae ( Opiliones ) Dermaptera, and Carabidae were common in pitfall samples Asin and Pons (1999) found additional corn field predators in the famil ies Chrysopidae (Neuroptera) and S yrphidae (Diptera) that were aphid spec ialists Eckert et al. (2006) in Bonn, western Germany found arthropods on silk and husk s to be in different feeding groups such as herbivores [i.e., aphids (Hemiptera: Aphididae) thrips (Thysanoptera: Thripidae) and leafhoppers (Hemiptera: Cicadellidae )], saprophytes ( i.e., beetles), predators ( i.e., lacewings and minute pirate bugs ), and parasitoids (Hymenoptera). He further suggested that sampling corn ears is a good method to find changes in arthropod abundanc e of specific feeding groups. The potential of a predator to control a pest species can be determined by evaluating how it affects population dynamics of the pests over a prol onged time period (Brodeur 2006, Jafari and Goldasteh 2009). Because it is imp ortant to know the efficacy of a natural enemy before us ing it in a biocontrol program, an important first step is studying behavioral characteristics of the natural enemy directed towards its prey. One method for study ing the efficacy of a natural enemy species is measuring its

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30 functional response. Solomon (1949) defined functional response as a measure of the number of prey attacked per predator at a given prey density. The f unctional response is very useful for studying predator prey relationships be cause it indicates the ability of a predator to regulate prey density ; specifically, how a predator increases or decreases its prey consumption with changing prey density (Hassel l 1978, Livdahl and Steven 1983). Th e capacity to regulat e prey density can b e estimated by two parameters: handling time and attack constant. Handling time is the time required by a predator to encounter and eat its prey, and the attack constant is the time taken by predator to search for its prey (Ives et al. 1993). O bjectives of the present study were to 1 ) identify and determine the abundance of arthropod s pecies in corn ears in the field, 2 ) determine the spatial distribution of the predators found in ears relative to the spatial distribution of corn infesting Ulidiidae eggs and larvae, and 3 ) to determine the functional responses of selected predators to egg, larvae, and adults of Euxesta spp. ( i.e., E stigmatias E eluta and E annonae ) in the laboratory. Materials and Methods Field Preparation : The study was conducted at the Tropical Research and Education Center (TREC) Homestead, FL in a Krome gravelly loam soil ( 33% loamy soil and 67% limestone pebbles >2 mm). The study was replicated through time during the spring, summer and fall of 2010 eminis Vegetable Seeds Inc., Oxnard, C A ) was planted in rows using a precision garden seeder (Model 1001 B, Earthway P roducts, Inc. Bristol, IN) on 15 February, 2 June, and 1 October 2010 for the spring, summer, and fall tests, respectively. S eeds were planted 1 m apart

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31 within each row with 0.9 m between rows. Granular fertilizer ( 8 16 16 N P K) was applied at 1,347 kg/ha at planting in parallel band s spaced 0.1 m from the seed rows. In addition, liquid fertilizer (4 0 8, N P K) was applied as a folia r spray at 2.77 kg of N 2 /ha/d on the third and fifth week s after planting. The pre emergence herbicide t rifluralin (Treflan 4EC, Dow AgroSciences LLC, Indianapolis, I N USA) was applied at 0.09 kg/ha at planting. P lants were irrigated using drip irrigat ion as needed The sweet corn f ield s w ere sampled once during each of three ear development stages for studying abundance and spatial distribution of predatory arthropods in corn ears : R1 or silking stage (8 9 wk after planting), R2 or blister stage (10 14 d after first silk), and R3 m ilk stage (18 22 d after first silk) (Table 2 1) (Bean and Patrick 2011) According to Eckert et al. (2006), sampling ear s to determine arthropod speciation involves simple techniques that are easily performed in the labora tory and this sampling can be standardized in a cost effective manner. The first sampling date was 4 d after the first silk The economic ally important infestation by corn infesting Ulidiidae typically starts at the silking stage (Seal and Jansson 1993) E ggs deposited in corn silk a t this stage have a higher survivorship than on other oviposition sites on corn plants such as tassels or base s of leaf axils (Seal and Jansson 1993). The second sampling date during the R2 stage correspond ed with maximum emergence of ulidiid larvae from eggs (Seal and Jansson 1989). The final sampling date at the m ilk stage was chosen when corn silk began senesc ing and turning brown, because it was thought that ulidiids would be less common then because they prefer fresh silk for oviposition (Seal and

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32 Jansson 1993). At this last sample date kernels with a thick pasty endosperm fluid have undergone maximum damage from larval feeding. Seasonal Abundance and Diversity of Arthropods Each experimental field (0.4 ha) was div ided into four equal blocks each measuring 0.1 ha (i.e. 1 0 rows wide x 55 m long) with each block subdivided into ten plots of 2 rows wide x 27.5 m long, for pseudo replication. Such plotting of fields would be expected to reduce the effect of uncontrolle d variables on samples. Two corn ears (1/ plant ) were randomly collected from each plot on each sampling date during the 1, R2 and R3 stages (i.e., 80 corn ears per date). Each ear w as placed separately in a Z ip L ock bag (17 X 22 cm) and transferred to th e laboratory for further study where they were stored at 22 5C, 30 5 C and 26 5 during the spring, summer and fall 2010 experiments respectively. The ears were removed from storage, cut in half at the mid point of the ears and placed in a 100 ml beaker filled with 75% ethanol for 5 m to collect the arthropods within the ears T he corn husk silk and pieces of corn cob were rinsed in alcohol to wash out the arthropod content. Later the washed ears were carefully removed with forceps and were d iscarded. The alcohol rinse was filtered using a 25 m mesh USA Standard Testing Sieve (W. S. Tyler Co., Mentor, OH ) to collect all arthropods, including corn infesting ulidiid eggs and larvae All collected arthropods were remov ed from the filter and sa ved in 70% ethanol for later identification Arthropods were later identified to species where possible and counted using a microscope at 10 X magnification Unidentified s amples of each arthropod species were sent for identification and voucher specimen s submit ted to the arthropod collection

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33 at the Institute of Food and Agricultural Sciences, Florida Division of Plant Industry (DPI), Gainesville Florida. The count d ata for arthropod abundance were transformed using square root transformation to improve normality and homogeneity of variance. Transformed data was analyz ed using one way analysis of variance (ANOVA) (PROC GLM, SAS Institute 2003). The dependent variable was the season (i.e., spring, summer, fall) and the independent variables estimated were the mean number of arthropods during which the arthropods were collected. Non transformed means and standard errors of mean s (SEM) are reported in figures. Differences among mean (n=40) arthropod count s were h onestly signifi cant difference) test (P < 0.05). Data for abundance of eggs and larvae of corn infesting Ulidiidae were similarly analyzed using Spat ial Distribution of P redators and Corn Infesting Ulidii ds The data collected on seasonal abundance was also used to study w ithin field distribution s of corn infesting Ulidiidae eggs and larvae and other arthropods. Data on distribution patterns of predatory arthropod s and ulidiid eggs and larvae were analyzed using Taylor s power law (Taylor 1961), Iwao s patchiness regression (Iwao 1968) and the Index of dispersion (ID). These metrics have been used to examine distribution s of taxa ranging from protists to vertebrate s (Kilpatrick and Ives 2003). However n one of these models have been used in previous studies for determining distribution pattern s of predatory arthropod s of these flies In the present study, we applied these models to determine the distribution of the various arthropods found in corn ear

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34 T specific relationship s between the temporal or spatial variance ( s 2 ) of population abundance and their mean density per sample using the following linear regression model (in our case applied to predatory arthropod s and corn infesting Ulidiidae eggs and larvae) : log s 2 = log a + b log x where s lope ( b ) is the index of aggregation characteristics for a species and log a is a sampling factor (Southwood 1978) The value of b indicates if the distribution pattern is uniform, random or aggregated. The distributions are found to be uniform random, or aggregated when b < 1 b = 1 and b < 1 respectively Iwao (1967) mean crowding index ( m* ) and t he mean ( ) which is expressed as follows : m* + = + where m s 2 is the sample variance a nd t he intercept ( ) is an index of basic contagion, which measures the tendency toward crowd ing. S lope ( ) is the density contagiousness coefficient which has a similar function to the slope value ( b ) ; it describes uniform, random and aggregated dispersion s when < 1, = 1 and > 1, respectively. For both the Taylor parameters were estimated using a general linear regression model (PROC GLM SAS Institute 2003). The goodness of fit for data from each field test to both the linear models was evaluated using regr ession coefficient s ( r 2 ) test was used

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35 to determine whether the slopes ( b and ) of the two models were significantly different from 1. The Index of dispersion was calculated to determine within field distribution using the following formula: ID = s 2 / x where s 2 is the sample variance and x is the mean number of predatory arthropod s or corn infesting ulidiid eggs or larvae per sample. Populations with ID values not significantly different from zero are regularly distributed, while those with ID > 1 is aggregated Laboratory Evaluation of Arthropod Species for Predatory Status Art hropod collection: The study was conducted in summer and f all 2010 using 150 ear s collected each season from a sweet corn field at TREC Homestead, FL These were placed in 17 X 22 cm Z ip L ock bag s ( S.C. Johnson & Son, Inc., Racine, WI, USA) at 10 ears p er bag transported to the laboratory and then temporarily stored at 26 5 and 30 5 C for the spring and summer tests respectively After one hour corn ear tips (10 cm from top) were excised with a knife and inspected with a microscope at 10 X to co llect arthropods. Live immature and adult stages of predator species were removed from corn ears using a fine insect brush, and transferred to Petri dishes (10.5 cm diam eter ) each containing one individuals of a particular species Six individual of a si milar age group for each species were collected to study their predatory status on different life stages of corn infesting Ulidiidae The age group of each species was confirmed by visually observing their size and color of individuals.

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36 Predatory status experiment: Nymphs and adults of O. insidiosus 3 rd instar larvae of an unidentified rove beetle (Coleoptera: Staphylinidae ), and 3 rd instar larvae of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) removed from field collected ears were evaluated for predation of ulidiid immature stages These arthropods were selected, because they were already known to belong to the group of generalist predators. One predator belonging to a particular family and age was placed in a Petri dish along with honey a nd water as food (three sets of such Petri dishes were prepared). T he predator arthropod s were deprived of water and food for 24 h before being provided with ulidiid prey. In each Petri dish containing one predator was provided with 20 e ggs (24 h old) of E. stigmatias E. eluta and E. annonae were provided as prey (20 eggs or larvae/predator). In the second set of Petri dishes each predator was provided with twenty 1 st 2 nd and 3 rd larval instar (24 h old) of Euxesta spp. and in the third set each pre dator was provided with 20 adults of each Euxesta spp. (24 h old). Preys were supplied from separate lab oratory colon ies for each species as described below. Th e experiment was replicated twice for each predator with each prey type (eggs, larvae and adul t) The Petri dishes were checked at 24 h intervals to record numbers of eggs and larvae of corn infesting ulidiids Dead ( as evidenced by deflat ion ) or missing eggs and larvae were assum ed to fe e d upon by the predators Th e study was conducted in a grow t RH. Insect colony maintenance : Colonies were begun using 100 a dults of each of E stigmatias E eluta and E annonae collected from corn fields in summer 2010. Each Euxesta spp. w as reared in a separate cage ( 30.5 x 30.5 x 30.5 cm ) and all stages of

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37 each colony were maintained 30 5C. R earing methods w ere the same for all the fly species. Colonies were maintained using an artificial diet designed for beet armyworm (BAW, Southland Co Lake Village, AR ) and methods desc ribed by Seal and Jansson ( 1989 ). Adults were supplied with 1% honey solution and fresh water. The diet was prepared by adding h oney 0.5 ml and green food coloring agent 0.2 ml (ESCO Food Co., San Jose, CA ) to each 81 gm of dried diet along with 465 lite r of boiling water The color was added to facilitate fly oviposition by simulat ing the green color of corn silk or cob D iets were placed in plastic cups (28.3 g) ( Beltsville, MD, USA ) and attached to the ceiling s of cage s to facilitate ovipo sition by the adults To develop a homogeneous colony for each fly species, eggs were collected at 24 h intervals and then transferred to fresh BAW diet for larval emergence in the same environmental conditions as the adults. Freshly eclosed first insta r larvae were removed from the egg containers every 24 h and transferred to plastic cup s (28.3 g) containing BAW diet and allowed to complete development into pupae. The diet cups were checked every 4 h to remove pupae. The pupae ( 4 h old ) were washed gently with tap water to remove dietary residue and to reduce fungal infection. The p upa e w ere then air dried to remove excess water from the cuticle and placed in Petri dish es with a disk shaped moist filter paper (5 cm in diameter ) to avoid desiccation. Petri dish es containing pupae were placed in cages ( 30.5 x 30.5 x 30.5 cm ) to facilitat e adult emergence. P upae were checked every 2 h to collect newly emerged adults up to 2 h old. C olonies of each fly species were maintained th roughout the year until s pring 2011.

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38 Functional Response of O insidiosus to Eggs of E uxesta s p ecies A laboratory study to evaluate the functional response of O. insidiosus to eggs of Euxesta spp. was conducted at TREC Homestead, FL Eggs of E stigmatias E eluta and E annonae were obtain ed from a laboratory colony maintained for several generations as detailed above Orius insidiosus adults were obtained from Koppert Biological Systems (Romulus, MI USA ) The experimental unit for the f unctional respo nse study was the same plastic cups ( 28.3 g ) used for maintenance of the Euxesta spp. colonies. The cups themselves were used to support a layer of parafilm on which the predators were supplied with specific eggs densities; nothing was placed within the c ups. A single layer of parafilm was placed over each cup (3.5 cm diam ) and then depressed into the cup (2 cm) to form a n area in which the predator and prey were introduced (Fig. 2 1 ). P rey eggs were killed by c ooling to 2 C for 30 m prior to addition to the cups Euxesta spp. eggs (24 h old) were added to the cups at the prey densities of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 eggs per cup Only one species of Euxesta spp. eggs was placed in each cup to determine functional responses for O. insidiosus adults for each fly species eggs. One O. insidiosus adult was then added to each cup. To standardize predator responses, adult O. insidiosus were starved for 24 h before beginning each experiment. Droplets of water (2 or 3) were added to the paraffin layer as a source of moisture. After placing prey eggs with predators in to a cup, it was covered with a Petri dish lid to seal the experimental unit Eggs that were preyed upon by O. insidiosus became deflated with a visible air vacuole visible ( Figure 2 7). After a 24 h feeding period, the number of deflated eggs in

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39 each arena was counted. Deflated eggs were assumed to be attacked by O. insidiosus based on the observation and comparison with intact fly eggs in the absence of predators in a cont rol group. Each treatment (number of eggs per arena ) was replicated eight times Containers were excluded from the experiment and discarded if the predator died or larvae emerged from the eggs The predation data allows us to determine two important thi ngs about a given predator prey relationship : t he shape or type of functional response (Type I, II or II I ) as well as the handling time and attack constant. T he first step in analyzing predation data was to determine the type of functional response using a polynomial logistic regression model ( CATMODE SAS Institute 2003) The second step was to fit the mechanistic model (based on the type of functional response obtained) and estimate the parameters (i.e., handling time and the attack constant) using the NLIN procedure ( SAS Institute 2003 ). Because the number of prey eggs declined as they were consumed ( the eggs The t ype of functional response shown by the data was first determined by logistic regression model in PROC CATMODE ( SAS Institute 2003 ). The following model was used to determine shape s of the functional response curves : where N e is th e number of prey eaten N 0 the initial number of prey and P 0 P 1 P 2 and P 3 the parameters estimated using the CATMODE procedure ( SAS Institute

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40 2003 ). Hence, a polynomial equation describing the relationship between the proportion of eggs eaten at each p rey density and each initial prey density was determined. If the first term ( P 1 ) in the data analyzed wa s negative, the functional response for the predator wa s type II and if the first term wa s positive, the functional response wa s type III. Once the t ype of functional response was determined, data were fit to the random predator equation ( PROC NLIN SAS 2003 ) In the PROC NLIN procedure a non linear, least square regression of the number of flies eaten versus the number of flies offered was used to es timate and compare the different parameters of the functional response The results of this experiment determined that O. insidiosus responded in a type III manner (Hassell 1978) to varying prey densities; therefore, only the following equation was used to estimate the search rate and attack constant parameters : N e = N 0 {1 exp [ a T N 0 / (1+ b N 0 + a T h N 0 2 ) ]} In the Hassell equation, a is the instantaneous search rate or the attack constant ( time taken by a predator to search for its prey ), b is a const ant, T h is the handling time and T is total time available for O. insidiosus to search for and attack the prey eggs. Results Seasonal Abundance and Diversity of Arthropods Several species of arthropods were found in corn ears during the 2010 survey. Or ius insidiosus were found throug hout 2010 in sweet corn (Table 2 2 ). The adults and larvae of sap beetles, Lobiopa insularis Castelnau and Carpophilus lugubris Murray (Coleoptera: Nitudilidae) w as also found in sweet corn ears throughout 2010. Larvae of an unidentified rove beetle (Coleoptera: Staphylinidae) species were found in ears only during the summer of 2010. Unidentified species of b ook lice (Psocoptera) and earwigs

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41 (Dermaptera: Forficulidae) were found in the brown and dried corn silk. In figur es 2 2, 2 3 and 2 4 numbers of larval and of adult Nitidulidae are represented as cumulative mean s of both L insularis and C lugubris Spring 2010: T he only potential ulidiid predator arthropod found d uring the R1 stage was O. insidiosus (Fig. 2 2A ). The mean number of corn infesting Ulidiidae eggs was significantly greater than the larvae ( t = 10.89; df = 1 ,39; P < 0.002) (Fig. 2 2B) Predatory a rthropods found d uring the R2 stage (Fig. 2 3A ) included O. insidiosus unidentified species of thrips (Thy sanoptera: Thripidae ) and larval and adult Nitidulidae ( L insularis and C lugubris ) There were significant differences among numbers of different groups of arthropods found with the mean number of Nitidulidae larvae great est ( F = 10.19; df = 5; 39, P < 0.0005). The number of corn infesting Ulidiidae l arva e found w as significantly great er than the number of eggs ( t = 61.69; df = 1 39 ; P < 0.001) (Fig. 2 2B ). Similar results were found in the R3 stage ear samples compared with those from the R2 stage. During the R3 stage (Fig. 2 3A ), there were significant differences among numbers of predatory arthropods found in ears ( F = 17.49; df = 5 39 ; P < 0.0001) with the mean number of adult Nitidulidae greater than the other species Significantly more ulid iid larv ae were found in ears in this stage than eggs ( t = 48.2; df = 1 ,39 ; P < 0.0001) (Fig. 2 2B) Summer 2010 : There was a greater diversity of arthropods found in ears in the summer than in the spring ear samples. Ulidiid eggs and larvae also were mor e common in the summer than the spring ear samples. In the R1 stage (Fi g. 2 3A ), there

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42 were significant differences among the numbers of predatory arthropods found in the ears ( F = 21.67; df = 5 39 ; P < 0.0001) with the mean number of O. insidiosus great er than the other species As in the spring, t he mean number of corn infesting Ulidiidae eggs was significantly greater than the number of larvae ( t = 53.17; df = 1, 39; P < 0.0015) (Fig. 2 3B) In the R2 and R3 stages (Fig. 2 3A ), there were significant differences among numbers of predatory arthropods ( F = 61.13; df= 5 ,39 ; P < 0.0001 ; and F = 69.11; df = 5 39 ; P < 0.0001 respectively ) with the mean number of Nitidulidae larvae greater than the other species The mean number of corn infesting Ulidiida e larvae was significantly greater than the number of eggs in the R2 and R3 stages ( t = 69.66; df = 1 39; P < 0.0001 ; and t = 72.9; df = 1; P < 0.002 respectively ) (Fig. 2 3B) Fall 2010 : In the R1 stage (Fig. 2 4A ), T here were significant differences am ong the numbers of predatory arthropods found in ears ( F = 20.29; df = 5 39 ; P < 0.0001) with the mean number of O. insidiosus greater than the other species The mean number of corn infesting Ulidiidae eggs was significantly greater than the number of l arvae ( t = 10.98; df = 1 39 ; P < 0.0015) (Fig. 2 4B ). Results for ear samples were different in the fall, R2 stage sample than the previous two season samples. T here were significant differences among the numbers of insects found in the arthropod groups ( F = 23.37; df = 5 39 ; P < 0.003) with the mean number of O. insidiosus the greater than the mean number of nitidulids and other species (Fig. 2 4A ). Additionally, there was no significant difference between the m ean

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43 number of corn infesting Ulidiidae e ggs and larvae ( t = 10.45; df = 1 39 ; P < 0.06) (Fig. 2 4B) T here were significant differences among the numbers of predatory insects found in ears during the R3 stage ( F = 48.2; df = 5 39 ; P < 0. 005) with the mean number adult Nitidulidae greater tha n the other species (Fig. 2 5A ). The mean number corn infesting Ulidiidae larvae were significantly greater than the number of eggs ( t = 53.11; df = 1 39 ; P < 0.0002) (Fig. 2 4B) The mean number of O. insidiosus (adults and nymphs) was found to be great est during s ummer 2010 and least during s pring 2010 (Fig. 2 5 ). The numbers of corn infesting Ulidiidae eggs and larvae w ere each greatest during s ummer 2010 (Fig. 2 6 ). Spat ial Distribution of P redators and Corn Infesting Ulidiids Spring 2010 : (Table 2 4 ) During the R1 and R2 stages, O. insidiosus showed an aggregated distribution because the slopes ( b and ) for the linear regression model ( ) were significantly > 1 ( P < 0.05, Table 2 4 ). The coefficie nts of determina tion ( r 2 ) for both models indicated a good fit ; this was indicated r 2 value that was approximately equal to 1 (ranging between 0.97 to 0.99) The indices of dispersion (IDs) of 1.2 during R1 and 23.7 during R2 stage were each significantly > 1 ( P > 0.05) indicating an aggregated distribution for O. insidiosus in agree ment with the results from calculating patchiness models. However, O. insidiosus appeared to be randomly distributed at R3 stage (Table 2 4) b as ed on the slope values calculated from b = 0.86 and = 0.72) being significantly equal to 1

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44 ( P < 0.05) The ID value at R3 stage of 0.99 was not significantly different than 1 indicating a r andom distribution (Table 2 4) The distribution of Ulidiidae eggs and larvae was aggregated in all three ear stages sampled (i.e., silking, blister and milk stage s) (Table 2 2). This determination was based on the slope values ( b and ) being significantly > 1 ( ranging from 1.5 to 4.1)( P < 0.05, Table 2 4 ) models. An aggregated distribution was also indicated by the I ndex of dispersion model as the value was significantly greater than 1 (range: 1 .2 to 23.7 ) ( P < 0.05). The numbers of Ulidiidae larvae found in sampled ears during R1 stage were not great enough to estimate a distribution pattern (Table 2 4 ). However, a t both R2 and R3 stages, the larvae had an aggregated distribution based on slope s in Summer 2010 : (Table 2 5) showed aggregated distributions for O. Insidiosus during the R1 and R2 stage s (Table 2 5 ). The s lopes for Tay R1 and R2 stages were 2.35 and 1.92, R1 and R2 stages were 2.67 and 2.18, respectively. All these values were significantly greater than 1 ( P < 0.05) indicating ag gregated distribution pattern s Staphylinid larvae were not present during the R1 and R2 stages (Table. 2 5 ) They were distributed in an aggregated fashion at the R3 stage based on t he slopes for els.

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45 aggregated distributions for corn infesting Ulidiidae eggs throughout the R1 R2 and R3 stages of sweet corn (Table 2 5 ) due to slopes > 1 The ID values for all the three samp ling date s were also significantly > 1 ( P < 0.05) indicating an aggregated distribution The Ulidiidae larvae were low during the R1 stage ; their pattern of distribution patterns could not be determined At R2 and R3 stages ; however, these larvae showed a ggregated distributions (Table 2 5 ). patchiness of regression model were each significantly greater > 1 ( P < 0.05), as were ID values for each sampling date. Fall 2010 : All the models found distributions of O. Insi diosus aggregated during R1 AND R2 stage as slope values ( b and ) and ID values were significantly greater than 1 ( P < 0.05) (Table 2 6). During R3 stage the distribution was random slope values ( b and ) and ID values were significantly equal to 1 ( P < 0.05) The distribution of Ulidiidae eggs was aggregated during both R1 and R2 stages. As the number of Ulidiidae eggs was low during R3 stage, their pattern of distribution patterns could not be determined. At R2 and R3 stage, the Ulidiidae larvae displ ayed an aggregated pattern of distribution. Laboratory Evaluation of Arthropod Species for Predatory Status In the laboratory, all the three predator species chosen were found to fe ed up on corn infesting Ulidiidae species (Table 2 2,3 ). Both nymphs and a dults of O. insidiosus fed on eggs and larvae of E. stigmatias, E. eluta, and E. annonae (Figs. 2 7 and 2 8 ).

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46 Staphylinid larvae devoured eggs and larvae of Euxesta spp. (Fig. 2 9 ) and C carnea larvae (3 rd instar) fed on larvae and adults of Euxesta spp ( Fig.2 10 ). Functional Response of O insidiosus to Eggs of E uxesta sp ecies O rius insidiosus displayed a type III functional response to eggs of E. annonae E. e luta, and E. stigmatias because of positive first terms for linear regression equations of th e proportions of Euxesta spp. eggs consumed at each density versus initial egg density available to predators ( Table 2 7, Fig. 2 11 ). At the greatest prey density of 60 eggs per arena, O. Insidiosus fed on a n a verage of 39 E stigmatias eggs 40 E eluta eggs and 41 E annonae eggs There was no significant difference in the predation rates for O. insidious among three tested prey species ( F = 31.3 ; df = 2, 23 ; P < 0.00 1). Estimated handling times ranged from 0.43 0.45 h, while attack co nstants ranged from 0.03 0.05 for three Euxesta spp. eggs (Table 2 8 ). Discussion Our arthropod diversity results were consistent with other surveys of cornfield arthropods. A rthropods found within corn ears in this study were O. insidiosus unidentified thrips, unide ntified mites, beetles (adults and larvae of C. lugubris, L i nsularis ; and unidentified Staphylin id s ) and green lacewing larvae ( C carnea ). In all the three seasons, the most abundant arthropod species during silking was O. insidiosus followed by unide ntified thrips and mites. Knuston and Gilstrap (1989) also found O. insidiosus to be the most abundant predator account ing for 80% of total predators on corn. Eckert et al. (2006) reported Orius spp. were the most abundant predators when they surveyed th e fauna of maize ears Orius insidiosus occurred in spring, summer and fall of 2010 in sweet and field corn. Many authors reported that

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47 flowering corn plants during tasseling and silking strongly attract O. insidiosus as the host plant s harbor an abunda n ce of prey (Isenhour and Marston 1981, Elkassabany et al. 1996, Saulich and Musolin 2009). M ean number s of O. insidiosus w ere lowest during spring and greatest during summer. O rius insidiosus population s only consist of fertilized females d uring the spr ing because males reach 100% mortality due to cold winter (Saulich and Musolin 2009 ) We observed that during the R1 period, the mean number of corn infesting Ulidiidae eggs were greater than at either R2 or R3 stage Nuessly and Capinera (2004) reported that E stigmatias prefers to oviposit on fresh corn silk and oviposition on other plant parts such as corn leaves results in greater egg mortality With three seasons of data, we found that during the R1 stage when the mean number s of corn infesting Ul idiidae eggs were high, the first predators to colonize corn silk were O. insidiosus followed by smaller numbers of unidentified thrips and mites. Knuston and Gilstrap (1989) also observed that O. insidiosus was the first predator to colonize corn ears They found that O. insidiosus nymphs were abundant during the early silking stage which concurs with the present study where nymph populations were greatest during the silking stage and decreased during later developmental stages of corn. Th ese result s s uggest that O. insidiosus reproduced soon after colonization of corn fields, which is supported by Richie and Hanway (1984). Barber (193 6 ) also reported that O. insidiosus wa s the first arthropod to colonize corn ear s during silking stage. He further obs erved that as the growing season began O. insidiosus would first appear between the leaves and stalks of corn plants and later become more common on young tassel s He further noted that soon after first silk,

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48 Orius insidiosus travel ed to silk strands, wh ich provided a substrate for oviposition. As generalist predators, Orius spp. are common in different agricultural systems, where they serve as biological control agents in integrated pest management (Isenhour and Marston 1981, Isenhour and Yeargan 1981, Isenhour et al. 1990, Reid 1991, Bush et al. 1993). Baez et al. (2010) in Sinaloa, Mexico also reported Orius spp. feeding on different stages of E stigmatias O rius insidiosus adults are commercially available in Europe and the U S A. Therefore, furth er research to understand relationship s between O. insidiosus and Ulidiidae fly eggs and larvae is warranted But we should not ignore the fact that in Florida, farmers are treating the sweet corn fields multiple times a week with synthetic insecticides l ike pyrethroids, organophosphates and carbamates (Dr. G. L, Nuessly, Everglades Research and Education Center, pers. Commun.). He further suggested that the number of O. insidiosus in such commercialized sweet corn field is very low. As these pesticides are broad spectrum pesticides and they pose a great threat to the non target insects such as natural enemies (Kazmer and Brewer 2009). Therefore, the compatibility of these insecticides should also be tested with the survival of natural enemies such as O. insidiosus As ears developed through the R1 stage to R3 stage, the numbers of Ulidiidae eggs decreased while numbers of Ulidiidae larvae increased suggesting eggs were deposited in a fairly limited time period This may also be supported by the prefere nce of the pest for fresh corn silk for oviposition (Barber 1936) but as corn matures to the milk stage, the silk becomes dr y and brown colored. Similarly, O. insidiosus adult population s decreased as the corn matured from the R1 to R3 stage,

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49 which may h ave resulted from a lack of fresh corn silk rendering breeding conditions unfavorable (Barber 1936) A s imilar pattern of O. insidiosus abundance was reported in Ohio (Dicke and Jarvis 1962) and Kentucky (Isenhour and Yeargan 1981). Knuston and Gilstrap (1989) found the mean number of O. insidiosus was greatest during anthesis and whorl stage but the number declined as the corn silk became dried and brown during milk stage The abundance of O. insidiosus increased during summer 2010, similarly the abunda nce of corn infesting Ulidiidae eggs and larvae was greatest during the same season. Another predatory species found in corn ears was a n unidentified rove beetle larva ( Staphylinidae ) Its abundance was greatest during the summer of 2010 during the R3 st age. Everly (1935) studied arthropod compositions in corn fields of Ohio and found six different species of Staphylinidae including Atheta spp., Barydoma spp., Coproporus spp., Leptolinus rubripennis Lec., Mycetoporus spp., and Philonthus spp.. Atheta spp He collected the Coproporus spp. from corn plants, while the others were found on the ground (Everly 1935). Albajes et al. (2003) reported that 50% of the total rove beetles found in a corn field in Spain were in the genus Tachyporous A dults of the st aphylinid Stenus flavicornis Erichson have been shown to feed on egg masses of Ostrinia nubilalis Hbner in corn fields (Andow 1990). Several s taphylinid species are predaceous and potential biocontrol agents of agricultural pests (Cividanes et al. 2009). However, s taphylin i ds have been infrequently used in IPM programs owing to the lack of knowledge on their feeding preferences, ecology, and taxonom y (Balog et al. 2008, 2009; Balog and Marko 2008). The distribution pattern of Staphylinidae larvae was

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50 ag gregated during summer 2010 Most of the Staphylinidae larvae were found at R3 stage, entangled in the dried corn silk. of dispersion) were used to study the distribution pa ttern of corn ear associated arthropods, and corn infesting Ulidiidae eggs and larvae. All of these tools provided a reliable index for measuring their degree of aggregation that was determined by a coefficient of determination ( r 2 ): if the r 2 value is eq ual to 1 or approximately equal to 1, the model provides the best fit None of these tools have been used for measuring the distribution of corn infesting Ulidiidae eggs and larvae. However Goyal (2010) studied the distribution pattern of adult flies of E. stigmatias E. eluta and C. massyla caught in sticky trap s using His studies were conducted in both large and small scale fields during the time of first silk appearance until the time of corn ear harvest. He found that the distribut ion of flies was aggregated during most sampling dates in both the fields. Generally, insect population displays three types of distribution pattern: random, aggregated or uniform. According to Southwood (1978), the insect distribution is greatly influenc ed by their density within a field. He further stated, the distribution pattern is random if their density is lower due to low capture rate during sampling. er and they are more of ten caught during sampling Distribution of corn infesting Ulidiidae eggs and larvae was aggregated during all sampling dates. Gaurav (2010) found the distribution of adult Ulidiidae was mostly aggregated in sweet corn fields. However, in my studies dis tribution of larvae was not detected during the R1 stage, as larvae were either absent

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51 or very low at this time Similarly, the distribution pattern of O. insidiosus was aggregated in the majority of the sampling dates. Orius insidiosus displayed r andom distribution during R3 stage in summer 2010 and fall 2010 The random distribution occurred due to the low density of O. insidiosus that may be due to the lack of proper breeding conditions or lack of food at this stage of corn ear. In the laboratory, O. insidiosus had a type III functional response to eggs of Euxesta spp. A type III functional response, also known as an accelerating functional response, is a density dependent response typically exhibited by generalist predators (Murdoch and Oaten 1975). According to Hassel l et al. (1977), a type III functional response results in a sigmoid curve and is more characteristic of vertebrates than invertebrate predators or parasitoids. However, many invertebrates have also exhibited t ype III functional respon ses, such as Geocoris sp p feeding on cotton bollworm eggs (Shrestha and Parjulee 2004), O. insidiosus feeding on the Tetranychidae (Trombidiformes) Panonychus ulmi (Koch) and Tetranychus urticae (Koch) ( Ashley 2003) Possible reasons for the type III fun capacity to switch to different prey species, selective foraging in arenas of high prey density, and where learning and experience benefits the search for prey (Holling 1959b, Murdoch 1969, Schauber et al. 2004). Oriu s insidiosus is facultatively phytophagous and can feed on plant material during prey scarcity. Hence, it can maintain a high density during prey scarcity an important characteristic for a biological agent (Wiedenmann and ONeil 1991, Coll 1997). Ashley (2003) reported that Hemipteran predators including O. insidiosus limit their search area by high frequency turning

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52 movements followed by feeding until they reach a threshold time (selective foraging). In case of prey scarcity, the predators straighten t heir path to reach and exploit an area with a high prey density. These examples suggest explanations for the type III functional responses of O. insidiosus to Euxesta spp. eggs Type III functional response can also be observed in the corn silk that is ti ghtly packed and ulidiid eggs are present in clusters but randomly distributed. Orius insidiosus can easily feed on the eggs without making much movement, as eggs are present in clusters. Once the eggs are depleted it can feed on other prey like thrips ( which were also found in corn silk).

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53 Table 2 1. Planting and sampling dates for the sweet corn experiments. 2010 Planting First sampling Second sampling Third sampling Spring 02/15/2010 04/5/2010 04/19/2010 04/26/2010 Summe r 06/2/2010 07/28/2010 08/11/2010 08/18/2010 Fall 10/2/2010 11/19/2010 12/3/2010 12/10/2010 Table 2 2 Arthropods found in sweet corn during different season 2010.

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54 Table 2 3. Mean number ( SE) of Euxesta spp. (eggs, larvae and adults) eaten by gene ralist predators. Each predator was provided with 20 eggs, 20 larvae and 20 adults in separate Petri dish for 24 h. Euxesta spp. Euxesta stigmatias Euxesta eluta Euxesta annonae Generalist predators Eggs Larvae Adults Eggs Larvae Adults Eggs Larvae Adul ts 1 st 2 nd 3 rd 1 st 2 nd 3 rd 1 st 2 nd 3 rd Orius insidiosus adult 20 18.5 0.5 17.5 0.5 6.5 0.5 20 18.5 0.5 15 5.5 0.5 20 18.5 0.5 18 5.5 1 .5 4 th instar nymph 20 18 15 6.5 0. 5 20 17 14.5 1 .5 6.5 0.5 20 17 11.5 0.5 6.5 0.5 3 rd instar 17.5 0.5 16.5 0.5 12 4 16 16.5 0.5 12 4 16.5 0.5 16.5 0. 8 12 4 2 nd instar 14 15 9.5 0.5 2.5 0.5 13.5 0.5 15 11 3 11 15 9.5 0.5 4 1 st instar 6.5 0.5 7.5 0.5 3.5 0.5 6.5 0.5 7.5 0.5 3.5 0.5 6.5 0.5 7 .5 2 0 3.5 0.5 Staphylinidae (3 rd instar) 20 20 20 13 20 20 20 12.5 0.5 20 20 20 14 Chrysoperla carnea (3 rd instar) 15.5 0.5 9.5 0.5 3.5 0. 6 4.5 0.5 12 8.5 0.5 5.5 0.5 3.5 0.5 10.5 0.5 9.5 0. 5 3 5

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55 Table 2 4. parameters for distributions of predators ( Orius insidiosus adults and nymphs) and pests (Ulidiid ae eggs and larvae) in sweet corn ears during s pring 2010 at R1 R2 and R3 stages of corn g rowth Spring 2010, Orius insidiosus Stage of corn Plot size (Ha) Index of dispersion a b r 2 r 2 ID R1 0.6 0.87 2.32 AGG 0.99 1.37 7.29 AGG 0.97 1.20 AGG R2 0.6 0.36 2.03 AGG 0.98 1.08 3.34 AGG 0.99 2.96 AGG R3 0.6 0.18 0.86 R AN 0.99 0.05 0.72 R AN 0.98 0.91 R AN Spring 2010, Ulidiidae species eggs R1 0.6 1.55 4.1 AGG 0.99 1.61 3.39 AGG 0. 97 1.2 AGG R2 0.6 1.9 2.59 AGG 0.98 2.01 2.76 AGG 0.99 23.7 AGG R3 0.6 1.68 1.5 AGG 0.99 1.67 2.0 AGG 0.98 13.7 AGG Spring 2010, Ulidiidae species larvae R1 0.6 R2 0.6 25.3 20.1 AGG 0.98 36.13 14.7 AGG 0.99 18.0 AGG R3 0.6 2.83 4.12 AGG 0.99 15.61 2.48 AGG 0.98 7.71 AGG AGG , regular distribution: random distribution: b not significantly different from 1 (P > 0.05).

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56 Table 2 5 Tayl parameters for distributions of predators ( Orius insidiosus adults, nymphs, and Staphylinidae larvae) and pests (Ulidiid ae eggs and lar vae) in sweet corn ears during s ummer 2010 at R1 R 2 and R3 stages of corn growth. Summer 2010, Orius insidiosus Stage of corn Plot size (Ha) Index of dispersion a b r 2 r 2 ID R1 0.6 1.3 2.35 AGG 0.97 1.22 2.67 AGG 0.99 4.42 AGG R2 0.6 2.78 1.92 AGG 0.83 1.98 2.18 AGG 0.89 3.7 AGG R3 0.6 1.3 1.95 AGG 0.84 0.95 1.99 AGG 0.91 1.2 AGG Summer 2010, Staphylinidae larvae R1 0.6 R2 0.6 R3 0.6 1.24 3.21 AGG 0.98 2.22 3.09 AGG 0.99 5.6 AGG Summer 2010, Ulidiidae species egg R1 0.6 2.9 3.56 AGG 0.98 3.33 3.98 AGG 0.99 5.43 R2 0.6 1.65 4.32 AGG 0.89 0.98 3.76 AGG 0.81 5.01 R3 0.6 1.87 2.09 AGG 0.73 1.73 2.13 AGG 0.69 2.19 Summer 2010, Ul idiidae species larvae R1 0.6 R2 0.6 3.03 6.12 AGG 0.99 1.83 5.98 AGG 0.97 7.59 R3 0.6 4.1 3.09 AGG 0.97 2.43 4.04 AGG 0.98 9.65 AGG , regular distribution: random distribution: b not significantly different from 1 (P > 0.05).

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57 Table 2 6 parameters for distributions of predators ( Orius insidiosus adults, nymphs, and Staphylinidae larvae) and p ests (Ulidiid ae eggs and lar vae) in sweet corn ears during f all 2010 at R1 R2 and R3 stages of corn growth. Fall 2010, Orius insidiosus Stage of corn Plot size (Ha) Index of dispersion a b r 2 r 2 ID R1 0.6 1.05 1.82 AGG 0.99 10.20 1.75 AGG 0.97 9.4 AGG R2 0.6 0.21 1.62 AGG 0.99 0.64 2.28 AGG 0.99 1.12 AGG R3 0.6 0.12 0.96 R AN 0.99 0.19 0.94 R AN 0.99 0. 8 7 RAN Fall 2010, Ulidiide species eggs R1 0.6 0.18 1.86 AGG 0.99 0.05 1.02 AGG 0. 98 13.6 AGG R2 0.6 0.61 2.26 AGG 0.98 5.11 1.75 AGG 0.99 21.9 AGG R3 0.6 Fall 2010, Ulidiidae species larvae R1 0.6 R2 0.6 2.02 3.14 AGG 0.98 23.89 2.26 AGG 0.99 23.7 AGG R3 0.6 2.83 4.12 AGG 0.99 15.61 2.48 AGG 0.98 7.71 AGG AGG , regular distribution: random distribution: b not significantly different from 1 (P > 0.05).

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58 Table 2 7. Maximum likelihood estimates fro m logistic regression of proportion of prey eaten as a function of initial prey by Orius insidiosus adults. Table 2 8 Type III functional response of O. insidiosus to eggs of Euxesta spp. Euxesta sp p Handling time T h ( h ) Attack constant (h 1 ) E. stigmatias 0.45 0.02 0.03 0.05 E. eluta 0.43 0.04 0.03 0.02 E. annonae 0.44 0.05 0.05 0.01 Prey (eggs, n=60) Parameters Estimates SE 2 P Euxesta stigmatias Intercept ( P 0 ) 1.425 1.62 0.77 < 0.0001 Linear ( P 1 ) 0.628 0.147 18.37 < 0.0001 Quadratic ( P 2 ) 0.022 0.004 28.70 < 0.0012 Euxesta eluta Intercept ( P 0 ) 0.449 0.298 1.54 < 0.0001 Linear ( P 1 ) 0.356 0.16 29.67 < 0.0001 Quadratic ( P 2 ) 0.044 0.001 32.12 < 0.0024 Euxesta annonae Intercept ( P 0 ) 1.723 1.322 0.65 < 0.0001 Linear ( P 1 ) 0.799 0.031 19.27 < 0.0001 Quadratic ( P 2 ) 0.034 0.030 21.83 < 0.0011

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59 Figure 2 1. The experimental set up for functional response study.

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60 F igure 2 2 (A) (A) Mean number ( n=40) of potential predators of ulidiid corn pest found in corn e ars during s pring 2010 at three ear development stages. A= Orius insidiosus B = Unidentified thrips, C = Unidentified mites, D = Nitidulidae adults E = Staphylinid larvae, and F = Nitidulidae larvae. (B) Mean number of corn infesting Ulidiidae eggs and larvae. T bars above each column represent the SEM. M eans within a stage represented with the same letter

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61 Figure 2 3 (A) Mean number ( n=40) of potential predators of ulidiid corn pest found in corn ears during summer 2010 at three ear development stages. A= Orius insidiosus B = Unidentified thrips, C = Unidentified mites, D = Nitidulidae adults E = Staphylinid larvae, and F = Nitidulidae larvae. (B) Mean number of corn infesting Ulidiidae eggs and larvae. T bars above each column represent the SEM. M eans within a stage represented with the same letter

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62 Figure 2 4 (A) Mean number ( n=40) of potential predators of ulidiid corn pe st found in corn ears during fall 2010 at three ear development stages. A= Orius insidiosus B = Unidentified thrips, C = Unidentified mites, D = Nitidulidae adults E = Staphylinid larvae, and F = Nitidulidae larvae. (B) Mean number of corn infesting Uli diidae eggs and larvae. T bars above each column represent the SEM. M eans within a stage represented with the same letter

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63 Figure 2 5 Mean s easonal abundance of O. insidiosus during spring, s umme r and f all 2010. Each bar represents the mean SE (n = 120). T bars above each column represent the SEM. Means with the same letter are not significantly Figure 2 6. Mean s easonal abundance (n = 120) of Ulidiidae egg s and larvae during s pring, s ummer and f all 2010. T bars above each column represent the SEM. HSD).

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64 Figure 2 7 (A) The first instar nymph of O. insidiosus feeding on a Eu xesta stigmatias egg, (B) After three minutes, egg contents sucked out by O. insidiosus c reated an air vacuole inside the egg Figure 2 8 Adult O. insidiosus feeding on a third instar larva of Euxesta stigmatias.

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65 Figure 2 9 Staphylinid larva feeding on E uxesta stigmatias eggs. Figure 2 10 Larva of Chrysoperla carnea feeding on an adult Euxesta eluta fly.

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66 Figure 2 11 Type III functional response of Orius insidiosus to eggs of A) Euxesta stigmatias B) E. eluta, and C) E. annonae. Total t ime of exposure was 24 h.

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67 CHAPTER 3 DISTRIBUTION AND FUN CTIONAL RESPONE OF ZELUS LONGIPES (L.) (HEMIPTERA: REDUVIID AE) TO CORN INFESTIN G ULIDIIDAE FLIES (D IPTERA: ULIDIIDAE) Increasing concerns about infestation of sweet corn by picture winged flies (Dip Recently, Goyal et al. 2010 reported four species in two genera attacking corn in Florida: Euxesta stigmatias Loew, Euxesta eluta Loew and Euxesta annonae Fabricius and Chaetopsis massyla Walker. These flies deposit their eggs inside the corn silk at the tip of the corn ear (Seal et al. 1996). There are three larval instars. These larvae feed upon silk, corn kernel, and co rn cob (Nuessly and Capinera 2010). The damage caused due to larval feeding makes the corn unfit for eating. Chemical insecticides have always been a prevalent control for adult flies whereas other life stages remain protected. It was reported that serious injury might occur even after application of insectic ides (Seal 2001). Goyal (2010) reported these corn infesting Ulidiidae keep reentering the corn fields even after the application of insecticide. He further reported due to the lack of knowledge on economic threshold for these pests, growers are applying insecticides daily to keep the corn marketable (Goyal 2010). Nowadays awareness about the negative impacts of the chemical insecticides is growing rapidly. This has led to the greater adoption of biocontrol program in an integrated pest management. On ly a few natural enemies are known for the corn infesting Ulidiidae that including Orius insidiosus Say (Hemiptera: Anthocoridae) (Nuessly and Capinera 2010, Baez et al. 2010) which feed on eggs and larvae of these flies. Two parasitoids were reported to parasitize the pupae of Euxesta stigmatias that

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68 belonged to the families Pteromalidae ( Splangia spp.) and Eurytomidae (Baez et al. 2010). So far there have been no reports of a natural predator feeding or attacking the adults of the corn infesting Ulidiid ae Developing a biocontrol program strongly depends upon the ecological information about both the pest and its natural enemies in an agriculture system (Pearce et al. 2006). Information regarding the spatial distribution pattern of pests will help to de velop more targeted integrated pest management techniques. In addition the knowledge about ecological or physical factors of a predator will help to better assess its potentiality. Spatial distribution information further helps in development of efficien t sampling technique as well as realistic population models ( Boiteau et al. 1979 ). G oyal (2010) reported the spatial and temporal distribution of corn infesting Ulidiidae adults in heir aggregation. Many other tools are also available to measure the degree of aggregation Lloyds patchiness regression. None of these tools have ever been used to study th e spatial distribution of the corn infesting Ulidiidae and their natural enemies. The foraging success of a predator is dependent upon the prey dispersion pattern and interference produced by other predators present (Hassel 1980, S utherland 1983, Wilson 20 10). Predators aggregated around higher prey density displays functional and numerical response s The functional response refers to the change in prey consumption per unit time in relation to prey density (Hassel 1978, Cogni et al. 2000). It can also be explained as a behavioral response because it involves searching (Coll and Ridgway

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69 1995). Functional response plays a key role in determining the effectiveness of a predator for a biological control. The prey selection by the predator depends on the inve stment of it energetic values (Krebs and Davis 1993). These energetic values are two important parameters of functional response i.e., handling time and attack rate (Juliano 2001). T he handling time involves the subcomponents like time spent in attackin g and capturing prey, time spen t upon feeding, and time spent for digestive pause. The latter refers to the time period during which predator takes a rest before attacking another prey upon feeling hungry again (Holling 1963, Thompson 1975). Attack rate is dependent upon the probability of occurrence of factors such as predator prey encounter, predator attacking on encounter, and attacking resulting successful capture of prey (Holling 1963, Thompson 1975). For the present study, authors decided to test t he potentiality of Z longipes as a bio E. stigmatias, E. eluta, E. annonae and C. massyla adults in corn fields (Fig. 3 1). Zelus longipes (Hemiptera: Reduviidae) is a generalist predator, fee ding through extra oral digestion (Cogni et al. 2000, Kalsi and Seal 2011). All the life stages of this predator are known to serve as potential biological control agents (Unigarro 1958). It has also been reported to feed on another corn pest Spodoptera fugiperda Smith (Lepidoptera: Noctuidae) (Cogni et al 2000).

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70 The objectives of the present study were: ( i and ii ) to determine within plant and within plant distribution s of Z. longipes and corn infesting Ulidiidae, and iii) to determine the functional r esponse of the predator to adult stage Euxesta spp. These objectives were investigated to assess the potential of Z. longipes in controlling corn infesting Ulidiidae Materials and Methods In the following section within field and within plant distributio n of both Zelus longipes and corn infesting ulidiid has been described. Later in this section, methodology to study the functional response of Z. longipes (both male and female) to E. stigmatias, E annonae and E. eluta is described Field Preparation: The field study was conducted in Tropical research and Education Center (TREC) research fields, Homestead, Florida The soil type of the experimental field is Krome gravelly loam (loamy skeletal, carbonatic hyperthermic lithic Udorthents), which consists of about 33% loamy soil and 67% limestone pebbles (> V egetable S eeds, Inc., Oxnard, CA) was seeded using precision garden seeder (Model 1001 B, Earthway ) directly into the soil on rows in a 200m wide X 20 m long field on 5 October 2010. The seeds were planted 0.1 m apart within a row and 0.9 m between rows. Granular fertilizer 8 16 16 (N P K) at the rate of 1347 Kg/ha was applied at planting in a band 0.1 m from the seed rows. Supplemental liquid fertilizer (4 0 8, N P K) was applied foliarly to pla nts at the rate of 2.77 Kg/ha N /day on 26 October and 9 November 2010 ( i.e., third and fifth wk after plantin g, respectively). Halosulfuron (Sandea Gowan Company LLC, Yuma, Arizona) was applied at 0.20 kg/ha during la nd preparation 3 wk before planting seeds to control

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71 weeds. This field was used for both the experiments for within plant and within field distribution studies. Sampling dates and sampling time were also same for these two studies. Within Plant Distribut ion The experiment was organized as a simple plot design with four replications (blocks) 30 rows wide x 20 m long. Each block was subdivided into 12 plots, each 4 rows wide x 12.5 m long. The field was divided into subplots in order to increase the prec ision level and to reduce the experimental error or variability. Two such plots were randomly selected from each block for sampling at each date Sampling was conducted by visually inspecting five randomly selected plants/plot for adults of Z. longipes ( predator) and corn infesting Ulidiidae (prey) Each plant was inspected thoroughly (approximately 1minute/plant). Plants were divided into four strata for sampling purposes: basal leaves ( i.e., leaves on the lower three bands on the stem), middle leaves ( i.e.,, leaves above three collars band surrounding the corn ears), fruit (corn ear) and top/tassels ( i.e.,, all the portion above the middles leave). The number of target insects present was counted separately for each stratum. Plants were sample d three times per day beginning at the following times: 0900 1000, 1300 1400 and 1700 1800 h EST. Sampling was initiated at silking stage (R1 30 November) with additional sampling at blister (R2 10 December ) and milking (R3 17 December ) stages. Sampling time was initiated at the silking stage, because during the earlier vegetative stage s the numbers of both predators and p rey were very low.

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72 Data on within plant distribution were analyzed independently for each week and time interval. The count data was sub jected to log 10 (x+1) transformation to improve the normality and homogeneity of variance. As the objective was to determine abundance of adults of predators and prey on specified plant parts, data was analyzed using one way analysis of variance (ANOVA) ( PROC GLM, SAS Institute Inc. 2003). The ear age was used as a dependent variable. Independent variables were time and plant part. Untransformed means and the standard errors of the mean are reported in figures. Differences among mean numbers of adult o f Z. longipes and among corn infesting Ulidiidae significant difference) test ( P < 0.05). Within Field and Temporal Distribution The study was conducted in same field as above. The field wa s divided into 48 plots three rows wide x 12.5 m long (83.3 m 2 ) From each of these plots, five corn plants were selected randomly for non destructive visual sampling. Each plant was checked thoroughly (one minute/plant). The number of adults of Z. long ipes and corn infesting Ulidiidae ( Euxesta stigmatias, Euxesta eluta, Euxesta annonae and Chaetopsis massyla ) was recorded. Plants were sampled at three time intervals per day ( i.e., 0900 1000, 1300 1400 and 1700 1800 h EST), on the same sampling dates as indicated above for the within plant study. The data for each of these plots were later pooled for analysis in various combinations, forming variable sized plots for the study ( i.e., 0.15, 0.3 and 0.6 ha corresponding to 6, 12 and 24 combined plots, res pectively). Spatial and temporal distribution was determined by sample week for adults of both pest and predators on

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73 corn plant s using Taylor s power law (Taylor 1961), Iwao s patchiness regression (Iwao 1968), Index of dispersion and chiness tools. Methods for using Taylor s power law, Iwao s patchiness regression and Index of dispersion is same as described in materials and methods section of chapter 2. The Index of dispersion was calculated to determine within field distribution usi ng the following formula: ID = s 2 /x where s 2 is the sample variance and x is the mean number of predatory arthropod s or corn infesting ulidiid eggs or larvae per sample. Populations with ID values not significantly different from zero are regularly dist ributed, while those with ID > 1 is aggregated aggregation (Xiao et al. 1997): LIP = m*/m w here m = mean number of adults of Z. longipes adults of Z. longipes and corn infest ing Ulidiidae per sam ple m* = and s 2 = sample variance. If LIP > 1, it indicates an aggregated population whereas LIP < 1, indicates a random population. Functional R esponse of Zelus longipes to Euxesta stigmatias, Euxesta eluta an d Euxesta annonae Source of predator : To test the potentiality of Zelus longipes as a predator, male and female adults were collected from an abandoned sweet corn field in Homestead, FL and returned to the laboratory for feeding studies. Male x female pai rs were placed

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74 singly in four separate cages ( 30.5 x 30.5 x 30.5 cm ) at room temperature (30 5C). A moistened sponge (10 X 10 cm) placed on the floor of the dish to provide required humidity and it was replaced with another sponge once dried. Twenty, corn infesting Ulidiidae (24 h old) collected from lab reared colony, were added to the cage as a source of Z. longipes food. The cages were provided with water and 30% sugar solution in a glass vial covered with cotton ball (1 cm in diameter). These via ls in an inverted position were attached to the walls of the cage. The cages were checked every day for Z. longipes eggs Whenever eggs hatched, the first instar nymphs we re transferred to Petri dishes (10.5 cm in diameter) with a moistened filter paper (5 cm in diameter). Two first instar nymphs of Z. longipes were placed in each Petri dish. These instars were provided with four Ulidiidae larvae (2 nd or 3 rd instar, 24 h old) daily, as a source of food. These first instars were checked every day to co llect freshly molted second instars and other advance stages. All the stages were reared in similar manner until the adult stage. Rearing was continued until 16 (males and females) of Z. longipes adults were collected for the present study. Source of p est : Colonies were begun using 100 a dults of each of E stigmatias E eluta and E annonae collected from corn fields in summer 2010. Each Euxesta spp. w as reared in a separate cage ( 30.5 x 30.5 x 30.5 cm ) and all stages of each colony were maintained 3 0 5C. R earing methods w ere the same for all the fly species. Colonies were maintained using an artificial diet designed for beet armyworm (BAW, Southland Co Lake Village, AR ) and methods described by Seal and Jansson ( 1989 ). Adults were supplied wi th 1% honey solution and fresh water. The diet was prepared

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75 by adding h oney 0.5 ml and green food coloring agent 0.2 ml (ESCO Food Co., San Jose, CA ) to each 81 gm of dried diet along with 465 liter of boiling water The color was added to facilitate fly oviposition by simulat ing the green color of corn silk or cob D iets were placed in plastic cups (28.3 g) ( Beltsville, MD, USA ) and attached to the ceiling s of cage s to facilitate oviposition by the adults To develop a homogeneous colony for each fly species, eggs were collected at 24 h intervals and then transferred to fresh BAW diet for larval e mergence in the same environmental conditions as the adults. Freshly eclosed first instar larvae were removed from the egg containers every 24 h and transferred to plastic cup s (28.3 g) containing BAW diet and allowed to complete development into pupae. The diet cups were checked every 4 h to remove pupae. The pupae ( 4 h old ) were washed gently with tap water to remove dietary residue and to reduce fungal infection. The p upa e w ere then air dried to remove excess water from the cuticle and placed in Petri dish es with a disk shaped moist filter paper (5 cm in diameter ) to avoid desiccation. Petri dish es containing pupae were placed in cages ( 30.5 x 30.5 x 30.5 cm ) to facilitat e adult emergence. P upae were checked every 2 h to collect newly emerged adults up to 2 h old. C olonies of each fly species were maintained th roughout the year until s pring 2011. Functional Response Experiment: The functional response of Z. longipes adults (both male and female) to E. stigmatias E. annonae and E. eluta was measured in a feeding arena (circular plastic box 11.5 cm wide x 14 cm high) lined with moist foam at the base. The lid of the plastic boxes was fitted with fine mesh cloth (3.5 cm in diameter) to allow circulation. A glass vial with 5% honey solution fixed with a cotton

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76 plug was stuck to the wall of the box as a source of food for pest flies. The Z. longipes adults were provided with adults of E stigmatias, E. eluta and E. annonae each in batches of 2, 4, 6, 8 and 10 prey flies. Eight replicates were conducted at each fly density (simultaneously with a control in a sepa rate box) with each male and female Z. longipes adults. Replicates were discarded if the predator died during the 24 h feeding period. The E. stigmatias, E. eluta and E. annonae adults were refrigerated at 10C for 1 2 min to facilitate adding them to the feeding arenas without loss of adults. Predators were added to the arenas immediately following addition of the fly prey. One adult (male or female) was used in each feeding arena for each fly species. To standardize predator response, adult Z. longipe s were starved for 24 h before conducting this experiment. After a 24 h feeding period, the number of dead flies in each arena was counted. The dead flies recovered were considered attacked or fed by Z. longipes based on the observations as well as on co mparison with 100% survival of flies in absence of predators ( i.e., control). The predation data allows us to determine two important things about a given predator prey relationship : t he shape or type of functional response ( t ype I, II or II I ) as well as the handling time and attack constant. T he first step in analyzing predation data was to determine the type of functional response using polynomial logistic regression model ( CATMODE SAS Institute 2003) The second step was to fit the mechanistic model (based on type of functional response obtained) and estimate the handling time and attack constant parameters using the NLIN procedure (Juliano1993).

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77 Because the number of adult prey s, E stigmatias E eluta and E annonae declined as they were consume d ( the adults consumed were not replaced with new adults predator equation. The type of functional response shown by the data was first determined by logistic regression model in PROC CATMODE ( SAS Institute 2003 ). The CATMODE procedure is same as described as in materials and methods section of chapter 2. Once the type of functional response was determined, data were fit to the random predator equation ( PROC NLIN SAS 2003 ) In the PROC NLIN procedure a non linear, least square regression of the number of flies eaten versus the number of flies offered was used to estimate and compare the different parameters of the functional response (As the predatory data displayed only type II functional response, equation for type III functional response is not shown here). The following equation was used for a type II functional response: N e = N 0 {1 exp [a ( T h N e T ) ] } where a is the instantaneous search rate or the attack constant ( tim e taken by a predator to search for its prey ), b is a constant, T h is the handling time and T is total time available for Z. longipes to search for and attack the prey eggs. Results Within Plant Distribution All the four species of Ulidiidae (i.e., E. sti gmatias, E. annonae, E. eluta and C. massyla ) that are known to infest sweet corn in south Florida has been referred as corn infesting ulidiid in this chapter. Zelus longipes and corn infesting Ulidiidae started appearing in the corn fields before the eme rgence of tassel s Early in the vegetative

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78 stages, population abundance of Zelus longipes and corn infesting Ulidiidae was very low. Population increased thereafter with the progression of the season (Fig. 3 2), prior to tassel emergence (data not presen ted). At the R1 stage the Z. longipes population increased significantly on different locations within a corn plant, varying with daylight hours. The great est numbers of Z. longipes were recorded on the basal leaves, corn ears and top/tassels at 0900, 1300 and 1700 h EST, respectively (Fig. 3 2A, 2B and 2C). Corn infesting Ulidiidae showed a pattern of distribution similar to Z. longipes A similar pattern of within plant distribution was observed when plants were sampled at the R2 stage of ear devel opment. The mean number of Z. longipes was significantly great er on the middle leaves ( F = 4.02; df = 3, 192; P < 0.0084), fruits and top/tassels than on other plant parts at 0900, 1300 and 1700 h EST, respectively. At R2 stage very few adults were obse rved on the basal leaves irrespective of sampling time (Fig. 3 2D, 2E and 2F). The mean number of corn infesting Ulidiidae at 0900 h EST (R2 stage) was great e st on the middle leaves ( F = 9.23 ; df = 3, 192; P < 0.0001 ), followed by the basal leaves, and fr uit, while significantly lower on tassels than on other plant structures (Fig. 3 2D). At 1300 h EST, the mean number of corn infesting Ulidiidae was greatest on the fruit ( F = 18.54 ; df = 3, 192; P < 0.0001 ), followed by the middle leaves, basal leaves a nd tassel/top (Fig. 3 2E). At 1700 h EST, mean abundance of corn infesting Ulidiidae was greatest on top/tassels ( F = 41.94 ; df = 3, 192; P < 0 .0001 ), followed by the middle leaves and fruit No ulidiid adults were observed on the basal leaves at the 170 0h sample (Fig. 3 2F).

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79 During the R3 stage, the mean abundance of Z. longipes adults at 0900 h EST was greatest ( F = 32.29; df = 3,192; P < 0.0001) on the basal leaves, followed by the middle leaves fruits, and top/tassels (Fig. 3 2G). At 1300 h EST, the mean number of Z. longipes was greatest ( F = 27.15; df = 3, 192; P < 0.0001) on the fruits, followed by the middle leaves and basal leaves None of the predators were observed on top/tassels at 1300 h (Fig. 3 2H). At 1700 h EST, the mean number of Z. lon gipes was greater ( F = 18.46; df = 3, 192; P < 0.0001 ) on the tassel/top than on the basal leaves, middle leaves, and fruits (Fig. 3 2I). Corn infesting Ulidiidae showed a pattern of within plant distribution similar to Z. longipes across the three sampli ng times of a day (Fig. 3 2G, 2H and 2I). Within Field and Temporal Distribution Corn infesting Ulidiidae : Plot size did not have a significant affect on the distribution of the flies during the R1 stage A t 0900 and 1700 h EST, the slope s for both the Ta were significantly > 1 for all three modeled plot sizes (Table 3 1) indicating an aggregated distribution for adult ulidiids at the initiation of silking ( P < 0.05, Table 3 1). However, the distribution wa s determined to be random during the middle of the day at 1300 h EST because the slopes of these two equations were not significantly different than 1 ( P < 0.05). The coefficients of determinant ( r 2 ranged from 0.66 to 0.98 suggesting good fit of model The Index of dispersion and significantly >1 i.e., aggregated distribution while at 1300 h EST the values was n ot significantly different from 1 ( P > 0.05) suggesting random distribution.

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80 At the R2 stage, c orn infesting Ulidiidae were aggregated irrespective of sampling time based on the slopes of both models being significantly > 1 ( P < 0.05) (Table 3 2). The In 1300 and 1700 h EST showed value significantly >1 ( P < 0.05) suggesting aggregated distribution During R3 stage, c orn infesting Ulidiidae was distributed on corn plants as t hey were during the blister stage (Table 3 3). A t 0900, 1300 and 1700 h EST, the slope value s ere found to be significantly > 1 ( P < 0.05) (Table 3 3). The coefficients of determinant ( r 2 ) for thes e two patchiness for all the plot sizes at 0900, 1300 and 1700 h EST showed aggregated distribution as value s were significantly > 1 ( P < 0.05). Zelus longipes : Zelus lon gipes showed variable patterns of distribution in corn fields depending on ear stage and diel time of sampling. During the R1 stage, at 0900 h EST and 1700 h EST the slope ( b the entire plot sizes (Table 3 4) were not significantly different from 1 ( P < 0.05, Table 3 1), indicating random distribution pattern. were significantly > 1 (P < 0.05) for all the plot sizes indicated significant aggregation. The coeffici ents of determinant ( r 2 regression indicated a good fit of models to data of all the plot sizes. The Index of h EST show ed value not significantly different from 1 indicating lack of aggregation

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81 while at 1300 h EST the value was significantly > 1 (P > 0.05) indicating significant aggregation. Z. longipes populations were aggregated when corn plants were at R2 stage irrespe ctive of sampling time (Table 3 5 ). During week six at 09:00, 13:00 and 1700 h EST, the slope ( b and were found to be significantly > 1 ( P < 0.05) indicating aggregated distribution (Table. 3 5). The coefficients of determinant ( r 2 ) for these two models ranged from 0.68 to 0.99 indicating good fit of model, as these values were approximately equal to 1 The Index 0 h EST, 1300 h EST and 1700 h EST showed values significantly >1 ( P <0.05) indicating aggregated distribution of Z. longipes Zelus longipes distribution during R3 stage of sweet corn plants did not differ from the R2 stage sweet corn plants (Table 3 6 ). During R3 stage, at 0900, 1300 and 1700 h EST, the slope ( b and regression were found to be significantly > 1 ( P < 0.05) indicating aggregated distribution (Table 3 6). The coefficients of determi nant ( r 2 ) for these two models for the entire plot sizes at 0900, 1300 and 1700 h EST showed value significantly >1 ( P < 0.05) indicating aggregated distribution Fu nctional R esponse of Zelus longipes to Euxesta stigmatias, Euxesta eluta and Euxesta annonae Zelus longipes males and females adults showed a t ype II functional response to E. stigmatias E. eluta and E. annonae (Fig. 3 3 ) In functional response of male Z.

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82 longipes to E uxesta spp the handling time ( T h ) ranged from 1 to 1.5 h while female Z. longipes handled E uxesta spp within the time range of 0.67 to 0.97 h (Table 3 7). The attack rate constant ( a ) in both the cases of male and female Z. longipes ran ged from 0.05 to 0.08. Discussion Sweet corn provides a breeding substrate for ulidiid flies. Females prefer to lay eggs inside newly emerged silks at the tip of the corn ear. Oviposition decreases significantly as corn silk ages (Seal et al. 1996). In the present study corn infesting Ulidiidae abundance was very low before silking, which may be due to the lack of proper egg laying location. As the plant proceeded from R1 to R3 stage t he abundance of both corn infesting Ulidiidae and Z. longipes was fo und to increase significantly This result is in agreement with Seal et al. (1996) who mentioned that the density of E stigmatias continues to increase until three week after anthesis. The increasing predator density due to increasing prey number has be en supported by Rogers (1972) in the past, which may account for the higher abundance of Z. longipes with approaching corn development (R1 stage to R3 stage). Throughout the sampling period, prey predator density was found to be abundant on tassel at 1700 h EST. At 0900 1300 h EST the prey predator density was mostly varied on different parts of plants except the tassel. This can be supported by the observation made by Seal et al. (1996) who reported that E stigmatias showed peak oviposition behavior du ring early morning hours from 0900 to 1300 h EST. This is the time when fully gravid females aggregate around lower and middle region s of corn plants in order to oviposit inside the silk channels. They further observed variation in

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83 diel pattern of mating behavior, with most mating taking place in the evening near the tassel. Corn infesting Ulidiidae and Z. longipes showed aggregated as well as random pattern of distribution during the R1 stage of corn development. The occurrence of corn infesting Ulidi idae was observed at the onset of tassel emergence (vegetative stage) but the number was low. The adults of Z. longipes were observed two weeks after corn planting, but again their abundance was low. During the R1 stage, the corn infesting Ulidiidae star ted visiting the corn plants more frequently and started establishing itself. At this time its distribution was more random. Occurrence of corn infesting Ulidiidae changed the micro ecosystem of a corn plant, affecting distribution of other arthropods su ch as Z. longipes Rogers (1972) mentioned that predators adopt a random search strategy to find its prey, and search is independent of prey distribution. They further suggested that random attack strategy of a predator is a function of host density rath er than host distribution. During the R2 and R3 stages of corn development, the pattern of distribution was aggregated for both the flies and their predator, Z. longipes By this time both the pest and the predator were well established in the field. La ter in the season, with the increase in population density of corn infesting Ulidiidae the population tends to be aggregated and this further resulted in similar population structure of its predator Z. longipes This observation was in agreement with th e previous study done by Hassel (1978), who reported that at high densities many predators have shown an aggregated distribution.

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84 Zelus longipes exhibited a type II functional response to all th ree E uxesta spp. tested (Fig. 3 4). Hassel et al. (1977) sug gested that a generalist predator shows a type III functional response, as the population of generalist predators is independent of host densities. This occurs because a generalist predator can easily switch from one extinct host type to another. However in our lab experiment Z. longipes showed a type II response because the experiment was a no choice type, with only one prey type irrespective of different Euxesta spp. Thus, the predator did not have the choice of changing to different prey type. The ot her factor tested in this experiment was predator sex. It was observed that male Z. longipes took longer handling time as compare to the females. This may be due to the difference in the size of the predators, as males are smaller than females (Hart 1986 Kalsi and Seal 201 1 ). As has been already mentioned if the size of predator is small, the time to handle its prey increases and the ability to search new prey decreases. Future research is suggested in a corn field under environmental conditions to bet ter ascertain the potential of Z. longipes as a predator in an agro ecosys tem.

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85 Table 3 index of patchiness parameters for distribution of corn infesting Ulidiidae s ampled in a cornfield R1 stage (0900 h EST) Plot sizes Index of dispersion index of patchiness (ha ) a b r 2 r 2 ID 0.60 0.11 3.51 AGG 0.98 2.30 3.09 AGG 0.97 1.87 AGG 1.87 AGG 0.30 .043 1.31 AGG 0.91 0.38 7 1.54 AGG 0.9 2 1.91 AGG 1.92 AGG 0.15 0.03 1.14 AGG 0.82 0.247 1.22 AGG 0.75 1.98 AGG 1.98 AGG R1 stage (1300 h EST) 0.60 .23 0.67 R AN 0.98 0.56 0.69 R AN 0.96 0.63 RAN 0.67 R AN 0.30 .13 0.33 RAN 0.92 0.3 4 0.48 R AN 0.91 0.76 R AN 0.78 R AN 0.15 .12 0.28 RAN 0.67 0.88 0. 36 R AN 0.66 0.85 R AN 0.95 R AN R1 stage (1700 h EST) 0.60 038 2.89 AGG 0.97 075 2.98 AGG 0.98 1.50 AGG 1.51 AGG 0.30 0.17 1.90 AGG 0.79 0.66 1.83 AGG 0.85 1.47 AGG 1.4 7 AGG 0.15 0.13 1.15 AGG 0.71 0.67 1.85 AGG 0.73 1.5 1 AGG 1.49 AGG AGG, aggregated distribution, b significantly >1( P 0.05); REG, regular distribution, b significantly < 1 ( P 0.05); RAN, random distribution, b not significantly different from 1 ( P > 0.05)

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86 Table 3 index of patchines s parameters for distribution of corn infesting Ulidiidae sampled in a corn field AGG, aggregated distribution, b significantly >1( P 0.05); REG, regular distribution, b significantly < 1 ( P 0.05); RAN, random distribution, b not significantly different from 1 ( P > 0.05) R2 stage (0900 h EST) Plot sizes Index of dispersion index of patchiness ( ha ) a b r 2 r 2 ID 0.60 0.69 1 .63 AG G 0.90 1.70 1.45 AGG 0.91 1.0 6 AGG 1.05 AGG 0.30 0.72 1.73 AGG 0.71 1.56 1.76 AGG 0.80 1.05 AGG 1.06 AGG 0.15 0.56 1.56 AGG 0.75 1.17 1.59 AGG 0.75 1.01 AGG 1.0 6 AGG R2 stage (1300 h EST ) 0.60 0.17 2.4 AGG 0.98 1.75 3.23 AGG 0.97 1.76 AGG 1.6 5 AGG 0 .30 0.19 1.50 AGG 0.97 0.18 1.73 AGG 0.98 1.63 AGG 1.55 AGG 0.15 0.18 1.39 AGG 0.68 0.51 1.18 AGG 0.58 1.72 AGG 1.63 AGG R2 stage (1700 h EST) 0.60 0.36 5.54 AGG 0.99 5.93 5.90 AGG 0.99 1.4 AGG 1.31 AGG 0.30 0.12 3.48 AGG 0.65 2.42 3.22 AGG 0.61 1.45 AGG 1.34 AGG 0.15 0.11 1.40 AGG 0.61 0.13 1.48 AGG 0.60 1.48 AGG 1.37 AGG

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87 Table 3 index of patchiness parameters for distribution of corn infesting Ulidiidae sampled in corn field R3 stage (0900 h EST) Plot sizes power law Index of dispersion index of patchiness ( ha ) a b r 2 r 2 ID 0.60 2.60 4.1 8 AGG 0.96 2.64 1. 4 AGG 0.93 1 .7 7 AGG 1 .9 6 AGG 0.30 2.13 3.47 AGG 0.91 1.217 1.15 AGG 0.90 1 70 AGG 1 .9 5 AGG 0.15 1.60 2.42 AGG 0.97 1.03 4 1.08 AGG 0.95 1 .42 AGG 1 .89 AGG R3 stage (1300 h EST) 0.60 0.7 7 5.93 AGG 0.93 5.81 5.96 AGG 0.92 1.0 AGG 1.0 4 AGG 0.30 4.21 4.57 AGG 0.85 5.78 4.12 AGG 0.68 1.06 AGG 1.0 2 AGG 0.15 2.81 2.80 AGG 0.79 5.96 2.47 AGG 0.5 7 1.14 AGG 1.06 AGG R3 stage (1700 h EST) 0.60 0.76 2 79 AGG 0.96 0.5 5 2.78 AGG 0.95 2.12 AGG 1.32 AGG 0.30 0.24 1.06 AGG 0.67 0.74 1.05 AGG 0.83 1.94 AGG 1.2 8 AGG 0.15 0.53 0.4 6 AGG 0.58 2.12 0.73 AGG 0.54 2.1 2 AGG 1.39 AGG AGG, aggregated distribution, b significantly >1( P 0.05); REG, regular distribution, b significantly < 1 ( P 0.05); RAN, random distribution, b not significantly different from 1 ( P > 0.05)

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88 Table 3 index of patchines s parameters for distribution of Z. longipes adults sampled in a corn field R1 stage (0900 h EST) Plot sizes Index of dispersion index of patchiness ( ha ) a b r 2 r 2 ID 0.60 .1 8 0.4 8 R AN 1.0 0 .4 8 7 0.83 R AN 0.99 0.9 6 R AN 0.93 R AN 0.30 .23 0.65 R AN 0.71 0.91 0.60 R AN 0.78 0.8 4 R AN 0.8 1 R AN 0.15 .14 0.71 R AN 0.74 0.34 0.73 R AN 0.76 0.95 R AN 0.9 9 R AN R1 stage (1300 h EST) 0.60 0.8 6 2.6 5 AGG 075 4.13 5.78 AGG 0.91 1.17 AGG 1.4 5 AGG 0.30 .24 1.07 AGG 0.85 1.19 1.75 AGG 0.83 1.1 7 AGG 1.3 4 AGG 0.15 .99 0.88 AGG 0.76 0.28 1.58 AGG 0.72 1.06 AGG 1.03 AGG R1 stage (1700 h EST) 0.60 .48 0.89 R AN 0.83 0.23 0.86 R AN 0.89 0.8 2 R AN 0.56 R AN 0.30 .46 0.85 R AN 076 0.27 0.79 R AN 0.76 0.8 6 R AN 0.65 R AN 0.15 .19 2 0.72 R AN 0.75 0.07 0.60 R AN 0.7 0.9 0 R AN 0.76 R AN AGG, aggregated distribution, b significantly >1( P 0.05); REG, regular distribution, b significantly < 1 ( P 0.05); RAN, random distribution, b not significantly different from 1 ( P > 0 .05)

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89 Table 3 index of patchiness parameters for distribution of Z. longipes adults sampled in a corn field R2 stage (0900 h EST) Plot sizes atchiness regression Index of dispersion index of patchiness ( ha ) a b r 2 r 2 ID 0.60 0.42 1.3 8 AGG 0.98 0.27 2. 4 AGG 0.99 2.1 5 AGG 2.9 6 AGG 0.30 0.35 1.47 AGG 0.99 0.01 2.06 AGG 0.94 1. 67 AGG 1.8 2 AGG 0.15 0.29 1.37 AGG 0.85 0.48 1.37 AGG 0.74 1.7 4 AGG 2.27 AGG R2 stage (1300 h EST) 0.60 0.2 2 1.6 6 AGG 0.97 0.60 2.30 A GG 0.96 1.15 AGG 1.2 4 AGG 0.30 0.13 1.31 AGG 0.98 0.24 1.62 AGG 0.98 1.1 8 AGG 1.27 AGG 0.15 0.07 1.08 AGG 0.87 0.13 1.02 AGG 0.68 1.1 4 AGG 1.2 4 AGG R2 stage (1700 h EST) 0.60 0.24 2.06 AGG 0.96 1.09 2.83 AGG 0.98 1.44 AGG 1.47 AGG 0.30 0.02 1.04 AGG 0.83 0.022 1.10 AGG 0.74 1.12 AGG 1.35 AGG 0.15 0.01 1.10 AGG 0.75 0.05 1.13 AGG 0.79 1.04 AGG 1.07 AGG AGG, aggregated distribution, b significantly >1( P 0.05); REG, regular distribution, b significantly < 1 ( P 0.05); RAN, random distribution, b not significantly different from 1 ( P > 0.05)

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90 Table 3 index of patchines s parameters for distribution of Z. longipes adults sampled in a corn field during R3 stage at different time intervals R3 stage (0900 h EST) Plot sizes Index of dispersion index of patchiness (Hec tare) a b r 2 r 2 ID 0.60 0.01 1.27 AGG 0.99 0.17 1.20 AGG 0.99 1.15 AGG 1.09 AGG 0.30 0.10 2.79 AGG 0.99 1.97 3.27 AGG 0.99 1.04 AGG 1.12 AGG 0.15 0.08 1.97 AGG 0.79 0.77 2.06 AGG 0.59 1.20 AGG 1.19 AGG R3 stage (1300 h EST) 0.60 0.10 2.58 AGG 0.99 1.75 3. 02 AGG 0.98 1.32 AGG 1.28 AGG 0.30 0.04 1.5 AGG 0.97 0.51 1.62 AGG 0.99 1.34 AGG 1.27 AGG 0.15 0.1 0.44 AGG 0.12 0.76 1.02 AGG 0.57 1.31 AGG 1.16 AGG R3 stage (1700 h EST) 0.60 0.17 1.43 AGG 0.98 0.10 1.58 AGG 0.99 1.59 AGG 1.49 AGG 0.30 0.12 1.87 AGG 0.99 0.77 2.1 AGG 0.98 1.53 AGG 1.37 AGG 0.15 0.15 1.59 AGG 0.83 0.57 2.01 AGG 0.63 1.63 AGG 1.41 AGG AGG, aggregated distribution, b significantly >1( P 0.05); REG, regular distribution, b significantly < 1 ( P 0.05); RAN, random distribution, b not significantly different from 1 ( P > 0.05) Table 3 7. Parameters (means S.E) estimated by random predator equation, indicting functional response of Ze lus longipes (male and female) to densities of Euxesta stigmatias Euxesta eluta and Euxesta annonae adults. Zelus longipes Male Corn infesting Ulidiidae Functional Type Handling time T h (h) Attack constant (h 1 ) Euxesta stigmatias II 1.12 2.25 0.07 0.03 Euxesta eluta II 1.0 1.23 0.06 0.02 Euxesta annonae II 1.39 1.27 0.07 0.02 Zelus longipes Female Euxesta stigmatias II 0.97 1.25 0.06 0.02 Euxesta eluta II 0.67 1.81 0.05 0.03 Euxesta annonae II 0.82 1.36 0.05 0.02

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91 Fig ure 3 1 Zelus longipes female feeding on Euxesta stigmatias in sweet corn field.

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92

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93 Figure 3 2. Mean number of Z. longipes and corn infesting Ulidiidae adults per time interval in various plant parts sampled in sweet corn field during R1 R2 and R3 s tage (a, b, c indicates significant difference in mean number of Z. longipes and A, B and C indicates significant difference in mean number of Corn infesting Ulidiidae (here Euxesta spp.) collected from various plant parts using ANOVA (at = 0.05). A) Z. longipes : F = 4.13; df = (3,192); Pr < 0.072; Euxesta spp: F = 3.32 ; df = (3,192); Pr < 0.021 B) ) Z. longipes : F=5.19; df=(3,192); Pr < 0.018; Euxesta spp: F = 13.17 ; df = (3,192); Pr < 0.001 C) Z. longipes : F = 4.07; df = (3,192); Pr < 0.021 ; Euxesta spp: F = 15.30 ; df = (3,192); Pr < .0001. D) Z. longipes : F = 4.02; df = (3,192); Pr < 0.0084; Euxesta spp: F = 9.23 ; df = (3,192); Pr < 0.0001 E ) Z. longipes : F=14.09; df=(3,192); Pr < 0.0001; Euxesta spp: F = 18.54 ; df = (3,192); Pr < 0.0001 F) Z. longipes : F = 7.9; df = (3,192); Pr < 0.0001 ; Euxesta spp: F = 41.94 ; df = (3,192); Pr < .0001. G) Z. longipes : F = 32.29; df = (3,192); Pr < 0.0001; Euxesta spp: F = 105.9; df = (3,192); Pr < 0.001 H) Z. longipes : F = 27.15 ; df=(3, 192); Pr < 0.0001; Euxesta spp: F = 78.96 ; df = (3,192); Pr < 0.001 I) Z. longipes : F = 18.46; df = (3,192); Pr < 0.0001 ; Euxesta spp: F = 58.53 ; df = (3,192); Pr < .0001

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94 Figure 3 3. Type II functional response of male Zelus longipes to Euxest a stigmatias (A), Euxesta eluta (B) Euxesta annonae (C) and type II functional response female Zelus longipes to Euxesta stigmatias (D), Euxesta eluta (E) Euxesta annonae (F). The graph represents mean number of prey eaten v/s mean umber of initial prey a vailable.

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95 Figure 3 4 Adult male, Z. longipes feeding on Euxesta annonae adult in lab experiment.

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96 CHAPTER 4 CONCLUSION S The four species of Ulidiidae (Diptera) Euxesta stigmatias Euxesta eluta Euxesta annonae and Chaetopsis massyla were found to infest sweet corn in southern Florida during the present study. The corn plant injury due to larval feeding includes rotting and clipping of silk, pollination disruption, poor kernel set, hollowing of kernel, feeding through entire corn ear and rotting o f ear due to fungal infection. At the peak level of larval injury, the yield reduction could reach to 100%. Even after the application of insecticides, significant injury is known to occur to the corn plant. Severe larval infestation usually makes corn unmarketable. Growers apply insecticides multiple times a week to control adult flies. Such application of insecticides makes the management of this pest costly. Thus, the demand for a sound integrated pest management program comprising chemical insecti cides and bio control agents seem to be a viable alternative for growers for corn infesting Ulidiidae. Such program needs detail information about biology of pests and their natural enemies. My research dealt with surveying sweet corn fields for natura l predator which feed on different life stages of the corn infesting Ulidiidae found in the sweet corn field in Homestead, and measuring the potential of these natural predators. Abundance and diversity of different arthropods residing in corn ears along with the eggs and larvae of Ulidiidae flies were reported. The study was replicated through spring, summer and fall 2010. Each season sampling was done at three different reproductive stages of corn ear development (i.e., silking, blister and milk stage) The various arthropod found in sweet corn ear were O. insidiosus unidentified thrips, unidentified mites, of unidentified

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97 species of Staphylinidae larvae, larvae of Chrysoperal carnea and adults and larvae of Lobiopa insularis and Carpophilus lugubris Among these arthropods the most abundant predatory arthropod found in corn at silking stage was O. insidiosus The occurence of Orius insidiosus in corn ear silk coincided with the occurrence of Ulidiidae eggs. In the laboratory studies different aged nymphs and adults of O. insidiosus were found to feed on the eggs and all larval instars of E. stigmatias E. eluta and E. annonae Similarly, Staphylinidae larvae were also found to feed on the eggs and larvae of Euxesta spp. Spatial distribution of the se predatory arthropods in relation to eggs and larvae of corn infesting Ulidiidae was investigated. In majority of the samplings, both the pest and predator were found to be aggregated in corn fields and in few cases they were found to be randomly distri buted. In the laboratory experiment, O. insidiosus displayed type III functional response to the 24 h old eggs of E. stigmatias E. eluta and E. annonae The handling time and attack rate was also measured. Information is available on natural enemies f eeding on the eggs, larvae and pupae of corn infesting ulidiid, but there are no reports of a natural enemy feeding on adult flies. Effort was made to find if there were any natural enemies that feed on different stages corn infesting ulidiids. The study was conducted in fall 2010 to identify potential predators of adult pest flies in a sweet corn field in Homestead, Florida. The adults of Zelus longipes were found feeding on the adult flies of E stigmatias E eluta E annonae and C massyla in the sw eet corn fields Further studies were conducted to find within corn plant distribution and spatio temporal distribution of both prey and

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98 predator in the sweet corn field. Zelus longipes started visiting the field after two weeks of corn planting while co rn infesting Ulidiidae were observed around tassel maturity (6 or 7 th wk after corn planting). It was observed that the mean number of both the Ulidiidae adults and Z. longipes continued to increase from silking stage to milk stage. Throughout the sampli ng period, the density of both insects followed the same pattern of within corn plant distribution. The density of corn infesting Ulidiidae and Z. longipes was higher on base leaves (present on lower three collar bands of stem), middle leaves (on collar b and around the corn ear) and fruits (corn ear) at 0900 and 1300 h EST. whereas the density of prey and predator both was higher on top or tassel (portion above the corn ear) at 1300 h EST. The pattern of distribution of corn infesting Ulidiidae and Z. lon gipes was random or aggregated during the silking stage but at later stages (blister and milk stage) their distribution was aggregated. Zelus longipes adults (both male and female) displayed type II functional response to the adults of E stigmatias E e luta and E annonae in the laboratory experiment. The male Z. longipes was found to take longer handling time as compare to the female adults. The spatial distribution studies were conducted to understand the predator prey dynamics in the corn field. T he action potential of these pests is yet to be established, so the information gained on the distribution of their population and predator can help in more targeted management of the Ulidiidae corn pest i.e., precision integrated pest management. Further more combining the spatial distribution data of the natural enemy with various physical and environmental factors will help to better understand their ecological needs. Ultimately this research would help in using beneficial insects in

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99 management of corn infesting Ulidiidae in sweet corn. The use of chemical insecticides will be continued to control Euxesta spp. until the establishment of effective biological control. Therefore, the spatial distribution pattern of pest and predator will help to reduce us e of insecticides by site specific application. Secondly, the time specific spray of these chemicals will promote the natural enemy survival. Future study should also include the testing of these insecticides on survival rate of the natural enemy on Ulid iidae pest of corn. The functional response helps to understand if the predator is efficient in regulating the pest population i.e., how predator would react to higher or lower density of the pest. Ideally in a functional response study at a higher prey density, the predator should display increased prey consumption. This produces a type III functional response with a sigmoid curve. Such type of functional response mostly occurs in a field as predator has greater chances of switching over preys. Thus, field studies involving functional response of potential predators O. insidiosus and Z. longipes to Ulidiidae corn pest is suggested. This will give an idea about how the predator reacts to different prey options in the field, helping in developing more efficient biocontrol program.

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100 LIST OF REFERENCES AgMRC (Agriculture Marketing and Resource Center). 2010. http://www.agmrc.org/commodities__products/grains __oilseeds/corn/sweet_corn.cfm Albajes, R. C. Lopez, and X. Pons. 2003. Predatory fauna in cornfields and response to imidacloprid seed treatment Journal of Economic Entomology 96 : 1805 1813 Allen, E. J., and B. A. Foote. 1967. Biology and imm ature stages of three species of Otitidae (Diptera) which have saprophagous larvae. Annals of the Entomological Society of America 60: 826 836. Allen, E. J., and B. A. Foote. 1975. Biology and immature stages of Tritoxa incurva (Diptera: Otitidae). Pro ceedings of the Entomological Society of Washington 77: 247 257. Allen, E. J., and B. A. Foote. 1992. Biology and immature stages of Chaetopsis massyla (Diptera: Otitidae), a secondary invader of herbaceous stems of wetland monocots. Proceedings of En tomological Society of Washington 94: 320 328. Andow, D. A., and S. J. Risch. 1985. Predation in diversified agroecosystems: relations between a coccinellid predator Coleomegilla maculata and its food. Journal of Applied Ecology 22: 357 372. Andow, D. A. 1990. Characterization of Predation on Egg Masses of Ostrinia nubilalis (Lepidoptera: Pyralidae) Annals of the Entomological Society of America 83: 482 486. Anonymous 2008. Florida Cooperative Agricultural Pest Survey Program. Quarterly report No. 2 2008. Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Gainesville, FL. App, B. A. 1938. Euxesta stigmatias Loew an Otitid fly infesting ear corn in Puerto Rico. Journal of Agriculture of the University of Puerto Rico 23: 181 187. Ashley, J. L. 2003. Toxicity of selected acaricides on Tetranychus urticae (Tetranychidae: Acari) and Orius insidiosus Say (Hemipter a: Anthocoridae) life stages and predation studies with Orius insidiosus M. S. Thesis. Virginia Polytechnic Inst ituted and State University Asin, L. and X. Pons. 1999 Effects of soil insecticide treatments on maize aphids and aphid predators in C atalonia Crop Protection 18 : 389 395 Andow, D. A. 1990. Characterization of Predation on Egg Masses of Ostrinia nubilalis (Lepidoptera: Pyralidae) Annals of the Entomological Society of America 83: 482 486.

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101 App, B. A. 1938. Euxesta stigmatias Loew, an otitid fly infesting ear corn in Puerto Rico. Journal of Agriculture of University of Puerto Rico 23: 1 8 187. Baez, I., S. R. Reitz., and J. E. Funderburk. 2004. Predation by Orius insidiosus (Heteroptera: Anthocoridae) on life stages and species of Frankliniella flower thrips (Thysanoptera: Thripidae) in pepper flowers. Environmental Entomology 33: 662 670. Bez, J. C. R, G. C. Garca J. I. V. Hernndez E. L. V. Montoya E N Prez D. B Armenta and M. M Ocampo 2010. Busqueda de enemigos naturales asociados de los estigmas Euxesta spp. (Diptera: Otitidae) En Maiz Blanco En Guasave, Sinaloa, Mexico Bailey, W. K. 1940. Experiments in controlling corn ear pests in Puerto Rico. Puerto Rico Experiment Station, circular no. 23, USDA, Mayaguez, P. R. Balog, A., J. Kiss, D. A. Szenasi, and V. Marko. 2009. Rove beetle (Coleoptera: Staphylinidae) com munities in transgenic Bt (MON810) and near isogenic maize Crop Protection 29 : 567 571. Balog, A., and V. Marko. 2008. Chemical disturbances effects on community structure of North West. Journal of Zoology 3: 67 74. Barber, G. W. 1936. Orius insidiosus (Say), an important natural enemy of the corn earworm. USDA Technical Bulletin 504. Environmental Entomology 22: 1192 1200. Barber, G. W. 1939. Injury to sweet corn by Euxesta stigmatias Loew in southern Florida. Journal of Economic Entomology 32: 879 880. Bean, B., and C. Patrick. 2011. Corn development and key growth stages. Texas A & M, Agricultural Research and Extension Center. Amarillo. Blanton, F. S. 1938 Some dipterous insects reared from narcissus bulbs. Journal of Economic Entomology. 31: 113 116. Boiteau, G., J. R. Bradley and J. W. Van Duyn. 1979. Bean leaf beetle: mi cro spatial patterns and sequential sampling of field populations. Environmental Entomology. 8: 1139 1144. Brodeur, J. 2006. The challenge of assessing efficacy of biocontrol agents against t.

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102 Brunel, O., and J. Rull. 2010. The natural history and unusual mating behavior of Euxesta bilimeki (Diptera: Ulidiidae). Annals of the Entomological Society of America 103: 111 119. Bush, L., T. J. Kring, and J. R. Roberson. 1993. Suitability of greenbugs, cotton aphids, Heliothes virescens eggs for development and reproduction of Orius insidiosus Entomologia Experimentalis et Applicata 67: 217 222. Carrel, J. E. 2001. Response of predaceous arthropods to chemically defended larvae of the pyr alid moth Uresiphita reversalis (Guene) (Lepidoptera: Pyralidae). Journal of the Kansas Entomological Society 74: 128 135. Cisneros, J. J and J. H. Rosenheim. 1997. Ontogenic change of prey preference in the generalist predator Zelus renardii and its influence on predator prey interactions. Ecological Entomology 22: 399 407. Cividanes, F. J., J. S. Barbosa, S. Ide, N.W. Perioto, and R.I R. Lara. 2009 Faunistic analysis of Carabidae and Staphylinidae (Coleoptera) in five agroecosystems in northeaste rn So Paulo state, Brazil. Pesquisa Agropecu ria Brasileira. 44: 954 958 Coderre, D., E. Lucas, and I. Gagne. 1995. The occurrence of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Canada. Canadian Entomologist 127: 609 611. Cogni R, A.V. L, Freitas, and F. A, Filho, 2000. Influence of prey size on predation success by Zelus longipes L. (He miptera: Reduviidae). Journal of Applied Entomology 126: 74 78. Cohen, A. C. 1990 Feeding adaptations of some predatory heteropterans Annals of Entomological Society of America 83: 1215 1223. Cohen, A. C and Tang, R. 1997. Relative prey weight influences handling time and biomass extraction Sinea confusa and Zelus renardii (Heteroptera : Reduviidae) Environmental entomology 26: 559 565. Co ll, M., and D. G. Bottrell. 1991. Microhabitat and resource selection of the European corn borer (Lepidoptera: Pyralidae) and its natural enemies in Maryland field corn. Environmental Entomology 20: 526 533. Coll, M., and D. G. Bottrell. 1992. Mortal ity of European corn borer larvae by natural enemies in different corn microhabitats. Biological Control 2: 95 103. Coll, M and L. R. Ridgeway. 1995. Functional and numerical response of Orius insidiosus ( Heteroptera: Anthocoridae ) to its prey in di fferent vegetable crops. Annals of Entomological Society of America 88: 732 738.

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103 Corey, D. 1994. Field, molecular and laboratory observations of Orius insidiosus (Hemiptera: Anthocoridae), a predator in corn. M. S. Thesis, Kansas State University. Core y, D., S. Kambhampati, and G. Wilde. 1998. Electrophoretic analysis of Orius insidiosus (Hemiptera: Anthocoridae) feeding habits in field corn. Journal of Kansas Entomological Society 71: 11 17. Cortez, M. E. 2008. Recomendaciones para el control de gusano cogollero y mosquita pinta en maz, en primavera verano Panorama Agropecuario, Los Mochis, Sinaloa, Mxico 193:16 17. Curran, C. H. 1935. New American Diptera. The American Museum of Natural History. 812 :1 24. Daly, T., and D. G. Buntin. 2 005. Effects of Bacillus thuringiensis transgenic corn for Lepidopteran control on nontarget arthropods. Environmental Entomology 34: 1292 1301. Diaz Fleischer, F., and M. Aluja. 2000. Behavior of tephritid flies: a historical perspective, pp. 39 72. In M. Aluja and A. L. Norrbom (eds.) Fruit flies (Tephritidae): phylogeny and evolution behavior. CRC, Boca Raton, FL. Dicke, F. F., and J. L. Jarvis. 1962. The habits and seasonal abundance of Orius insidiosus (Say) (Hemiptera Heteroptera: Anthocor idae) on corn. Journal of the Kansas Entomological Society 35: 339 344. Duffie, W. D., M. J. Sullivan, and S. G. Turnipseed. 1998. Predator mortality in cotton from different insecticide classes, pp. 1111 1112. In Proceedings, Beltwide Cotton Conferenc e, 5 9 January, 1998, San Diego, CA. Eckert, J., I.Schuphan, L. A. Hothorn, and A. Gathmann. 2006. Arthropods on maize ears for detecting impacts of Bt maize on nontarget organisms. Environmental Entomology 35: 554 560. Evans, D. C., and E. Zambran o. 1991. Insect damage in maize of highland Ecuador and its significance in small farm pest management. Tropical Pest Management 37: 409 414. Evenhuis, N. L. 1997. New records, synonymies, and range extension of two winged flies (Diptera) from the Ha waiian Islands, pp. 29 32. In Records of the Hawaiian biological s urvey for 1996, part 2: Notes Bishop Museum Occasional Papers. Vol. 49.

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104 Everly, R.T. 1 938. Spiders and insects found associated with sweet corn with notes on the food habits of some sp ecies. I. Arachnida and Coleoptera. Ohio. Journal of Science 38: 136 148. Ewert, M. A., and H. C. Chiang. 1966. Dispersal of three species of coccinellids in corn fields. Canadian Entomologist 98: 999 1003. Fantinou, A. A., D. C. Perdikis, and C. S. Chatzoglou. 2003. Development of immature stages of Sesamia nonagrioides (Lepidoptera: Noctuidae) under alternating and constant t emperatures. Environmental Entomology 32: 1337 1342. Fisher, E. 1996. Two new insect pests of corn in California New p es t/ d isease Advisory, 31 December 1996. State of California, Department of Food and Agriculture, Division of Plant Industry. Fox, T.B., D.A. Landis, F.F. Cardoso, and C.D. DiFonzo. 2004. Predators suppress Aphis glycines Matsumura population growth in soy bean. Environmental Entomology 33: 608 618. Franca, F. H., and P. T. D. Vecchia. 1986. Damages caused by Euxesta stigmatias on carrot roots in commercial seed field. Pesquisa Agropecuria Brasileira, Brasilia 21: 789 791. Fras, D. L. 1978. Estudio s ecol gicos en Euxesta eluta y Euxesta annonae (Diptera: Ottitidae). Agriculture technology. Chile. 38: 110 114. Funderburk, J., J. Stavisky, and S. Olson. 2000. Predation of Frankliniella occidentalis (Thysanoptera: Thripidae) in field peppers by Or ius insidiosus (Hemiptera: Anthocoridae). Environmental Entomology 29: 376 382. Gould, F. 1998. Sustainability of transgenic insecticidal cultivars: integrating pest genetics and ecology. Annual Review of Entomology 43: 701 726. Goyal, G. 2010. Mor phology, biology and distribution of corn infesting Ulidiidae. PhD Dissertation. University of Florida, Gainesville. Goyal, G., G. S. Nuessly, D. R. Seal, J. L. Capinera, G. J. Steck, and K. J. Boote. 2010. New report of Chaetopsis massyla (Diptera: Uli diidae) as a primary pest of corn in Florida. Florida Entomologist. 93 :198 202. Goyal, G., G. S. Nuessly, D. R. Seal, J. L. Capinera, G. J. Steck, and K. J. Boote. 2011. Corn infesting picture winged flies (Diptera: Ulidiidae) and their distribution in Florida. Florida Entomologist 94: 35 47.

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105 Greve L. 1998 Family Otitidae. In Papp L. & Darvas B. (eds): Contributions to a Manual of Palaearctic Diptera Higher Brachycera. Science Herald, Budapest 3: 185 192. Hall DG. 2008. Biological control of D iaphorina citri Concitver http://www.concitver.com/huanglongbingYPsilidoAsiatico/Memor%C3%ADa8%apdf Hansen, R. 2011. Agricultural marketing resource center. http://www.agmrc.org/commodities__products/grains__oilseeds/corn_grain/sweet_corn_ profile.cfm Harper, A. M. 1962. Life history of the sugarbee t root maggot in southern Alberta. Canadian Entomologist 94: 1334 1340. Hart, E. R. 1986. Genus Zelus Fabricius in the United States, Canada, and Northern Mexico (Hemiptera: Reduviidae). Annals of the Entomological Society of America 79: 535 548. Hassel l M. P. 1978. The dynamics of arthropod predator prey systems. Princeton University Press, New Jersey. Hassell, M. P. 1980. Foraging strategies, population models and biological control: a case study. Journal of Animal Ecology, 49, 603 628. Hassel l M. P, J. H, Lawton and J. R, Beddington. 1977. Sigmoid functional responses by invertebrate predators and parasitoids. Journal of Animal Ecology.46: 249 262. Hayslip, N. C. 1951. Corn silk fly control on sweet corn. University of Florida Agriculture E xperimental Station. Circular 41: 1 6. Hoffmann, M. P., M. S. Orfanedes, L. H. Pedersen, J. J. Kirkwyland, E. R. Hoebeke, and R. Ayyappath. 1997. Survey of lady beetles (Coleoptera: Coccinellidae) in sweet corn using yellow sticky cards. Journal of E ntomological Science 32: 358 369. Holling, C. S. 1959. Some characteristics of simple types of predation and parasitism. Canadian Entomologist: 91:385 398. Holling, C. S. 1963. An experimental component analysis of population processes. Memoirs of the E ntomological Society of Canada 32: 22 32. Holling, C.S. 1966. The functional response of invertebrate predators to prey densities. Memoirs of the American Entomological Society: 48:1 86.

PAGE 106

106 Hokkanen, H.M.T., and C. H. Wearing. 1994. The safe and rational deployment of Bacillus thuringiensis genes in crop plants: conclusions and recommendations of OECD workshop on ecological implications of transgenic crops containing Bt toxin genes. Biocontrol Science and Technology 4: 399 403. Hoy, C. W., J. Feldman, F. Gould, G. G. Kennedy, G. Reed, and J. A. Wyman. 1998. Naturally occurring biological controls in genetically engineered crops, pp. 185 205. In R. Barbosa (ed.), Conservation Biological Control. Academic, New York. Illingworth, J. F. 1929. Pests of pin eapple in Hawaii. Proceedings of the Hawaiian Entomological Society 7: 254 256. Isenhour, D. J. and N. L, Martson. 1981. Season cycles of O. Insidiosus in Missouri soyabeans and corn. Journal of Kansas Entomological Society. 54:129 142. Isenhour, D. J., and K. V. Yeargan. 1981. Effect of temperature on the development of Orius insidiosus with notes on laboratory rearing and a key to the nymphal stages. Annals of the Entomological Society of America 74: 114 116. Isenhour, D. J., R. C. Layton, an d B. R. Wiseman. 1990. Potential of adult Orius insidiosus as predator of the fall armyworm, Spodoptera frugiperda Entomophaga 35: 269 275. Ives, A. R., R. Kareiva, and R. Perry. 1993. Response of a predator to variation in prey density at three hie rarchical scales of lady beetles feeding on aphids. Ecology 74: 1929 1938. Iwao, S. 1968 A new regression model for analyzing the aggregation pattern of animal populations. Researches on Population Ecology 4: 35 46. Jafari, R., and S. Goldasteh. 20 09. Functional response of Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae) on Aphis fabae (Scopoli) (Homoptera: Aphididae) in laboratory conditions. Acta Entomologica Serbica. 14: 93 100. Jasinski, J. R, J. B. Eisley, C. E. Young, J. Kovach, a nd H. Wilson. 2003. Select nontarget arthropod abundance in transgenic and non transgenic field crops in Ohio. Environmental Entomology 32: 407 413. Jepson, P. C., B. A. Croft, and G. E. Pratt. 1994. Test systems to determine the ecological risks pose d by toxin release from Bacillus thuringiensis genes in crop plants. Molecular Ecology 3: 81 89.

PAGE 107

107 Jervis, M. A., and M. J. W. Copland. 1996. Insect natural enemies; Practical approaches to their study and evaluation, pp. 63 161. In M.A. Jervis and N. Ki dd (eds.), The insects: structure and function, Chapman & Hall, London. Checklist of Diptera of the Czech Republic and Slovakia. Department of Entomology, Silesian Museum. http://zoology.fns.uniba.sk/diptera2009/families/ulidiidae.htm Juliano, S. A. 2001. Non linear curve fitting: predation and functiona l response curves. Design and analyses of ecological experiments. 2 nd edition. (eds S.M. Scheiner and J. Gurevitch) pp. 178 196. Chapman and Hall, New York. Kalsi, M. and D. R. Seal. 2011. Featured Creatures. Milkweed assassin bug. Zelus longipes Linn aeus. http://entnemdept.ufl.edu/creatures/beneficial/bugs/zelus_longipes.htm Kameneva, E. P. 2004. New records of picture winged flies (Diptera: Ulidiidae) of Centra l America. Studia Dipterologica 10: 609 652. Kameneva, E. P. 2005. A new genus and species of tribe Lipsanini (Dipter: Ulidiidae) from Central America. Vestnik Zoologii 39: 97 101. Kameneva, E. P. 2006. East Asian and Papuan species of the genus He rina Robineau Desvoidy (Diptera, Ulidiidae, Otitinae). Instrumenta Biodiversitatis 7: 15 59. Kameneva, E. P. 2007. A new species of Hernia (Diptera: Ulidiidae) from Switzerland, with a key to European species and notes on nomenclature and distribution. Vestnik Zoologii 41: 405 421. Kameneva, E. P., and L. Greve. 2004. Fauna Europaea: Ulidiidae. Fauna Europaea: Diptera Cyclorrhapha. Fauna Europaea version 1.1. Ed. T. Pape. http://www.faunaeur.org Kawai, A. 1976. Analysis of the aggregation behavio r in the larvae of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) to prey colony. Research Population of Ecology (Kyoto) 18: 123 134. Kazmer D.J and M.l J. Brewer. 2009 Biological types of b iological c ontrol http://wiki.bugwood.org/HPIPM:Biological_Types_of_Biological_Control Kiman, Z. B., and K. V. Yeargan. 1985. Development and reproduction of the predator Orius insidiosus (Hemiptera: Anthocoridae) reared on diets of selected plant material and arthropod prey. Annals of the Entomological Society of America 78: 464 467.

PAGE 108

108 Knuston, A. E., and F. E. Gilstrap. Predator and Parasites of southwestern corn borer (Lepidoptera: Pyralidae) in Texas corn. Journal of the Entomological Society. 62: 511 520. Korneyev, V. A. 2000. Phylogenetic relationships among the Families of the Superfamily Tephritoidea, pp. 3 27. In M. Aluja and A. L. Norrbom (eds.), Fruit flies (Tephritidae): phylogeny and evolution of behavio r. CRC, Boca Raton, FL. Krebs, J. R and Davies, N. B. 1993 An introduction to behavioral ecology. Chapter.5. Managing time and energy. Oxford: Blackwell Science. Llyod, M. 1967. Mean crowding. Journal of Animal Ecology 36: 1 30. Livdahl, T. P., an d A. E. Steven. 1983. Statistical difficulties in the analysis of functional predator response. Canadian Entomology 115: 1365 1370. Lundgren, J. G., and J. K. Fergen. 2006. The oviposition behavior of the predator Orius insidiosus : acceptability and preference for different plants. Bio Control 51: 217 227. McAlpine, J. F. 1989. Manual of Neartic Diptera. Monograph 32. Agriculture Canada, Ottawa, ON, Canada. Merrill, L. S., Jr. 1951. Diptera reared from Michigan onions growing from seeds. Jour nal o f Economic Entomology. 14: 1015 1015. Morista, M. 1962 I o index, a measure of dispersion of individuals. Researches on Population Ecology 4: 1 7. Mossler, M. A. 2008. Crop profiles for sweet corn in Florida. Publication #CIR1233. http://edis.ifas.ufl.edu/pi034 Murdoch, W. W. 1969. Switching in general predators: experiments on predator specificity and stability of prey populations. Ecological Monographs 39: 335 354. Murdoch, W. W., an d A. Oaten. 1975. Predation and population stability. Advances in Ecological Research 9: 1 131. Musser, F. R., J. P. Nyrop, and A. M. Shelton. 2004. Survey of predators and sampling method comparison in sweet corn. Journal of Economic Entomology 97: 136 144.

PAGE 109

109 Nault, B. A., and G. G. Kennedy. 2000. Seasonal changes in habitat preference by Coleomegilla maculata : implications for Colorado potato beetle management in potato. Biological Control 17: 164 173. Nuessly, G. S., and J. L. Capinera. 2 010. Featured Creatures. Euxesta stigmatias Loew (Insecta: Diptera: Ulidiidae). http://entnemdept.ufl.edu/creatures/field/cornsilk_fly.htm Nuessly, G. S., K. Pernezney, P. Stans ley, R. Sprenkel and R. Lentini. 2010. Field corn insect identification guide. University of Florida. http://erec.ifas.ufl.edu/fciig/index.htm Nuessly, G. S., and J. L. Capinera. 2001. Online Publ ication. Featured Creatures. Entomology and Nematology Department, Institute of Food and Agriculture Sciences, University of Florida http://entnemdept.ufl.edu/creatures/field/corns ilk_fly.htm Nuessly, G. S., and M. Hentz. 2002. Evaluation of insecticides for control of fall armyworm in pre ear stage sweet corn, 2000. Arthropod Management Tests 27: E34. Entomological Society of America, http://entsoc.org/home?ip_login_no_cache=3489a43619412201c94e5f58c52b6320 Nuessly G. S., and M. G. Hentz. 2004. Contact and leaf residue activity of insecticides against the sweet corn pest Euxesta stigmatia s (Diptera: Otitidae). Journal of Economic Entomology 97: 496 502. Nuessly, G. S., B. T. Scully, M. G. Heintz, R. Beiriger, M. E. Snook, and N. W. Widstrom. 2007. Resistance to Spodoptera frugiperda (Lepidoptera: Noctuidae) and Euxesta stigmatias (Dipte ra: Otitidae) in sweet corn derived from exogenous and endogenous genetic systems. Journal of Economic Entomology 100: 1887 1895. Obrycki, J. J., J. E. Losey, O. R. Taylor, and L. C. H. Jesse. 2001. Transgenic insecticidal corn: beyond insecticidal tox icity to ecological complexity. BioScience 51: 353 361. Painter, R.H. 1955. Insects on corn and teosinte in Guatemala. Journal of Economic Entomology 48: 36 42. Pilcher, C. D., M. E. Rice., and J. J. Obrycki. 2005. Impact of transgenic Bacillus thu ringiensis corn and crop phenology on five nontarget arthropods. Environmental Entomology 34: 1302 1316.

PAGE 110

110 Ramachandran, S., J. Funderburk, J. Stavisky, and S. Olson. 2001. Population abundance and movement of Frankliniella species and Orius insidiosus i n field pepper. Agricultural and Forest Entomology 3: 1 10. Reid, C. D. 1991. Ability of Orius insidiosus to search for, find and attack European corn borer and corn earworm eggs on corn. Journal of Economic Entomology 84: 83 86. Ritchie, S. W., and J J. Hanway. 1984. How a corn plant develops. Iowa State University Cooperative Extension Service Report number 48. Rogers, D. 1972. Random search and insect populations models. Journa l of animal ecology 41 : 369 383. .B. Fox, and D.A. Landis. 2004. Soybean aphid predators and their use in integrated pest management. Annals of the Entomological Society of America 97: 240 248. Sabelis, M. W., and P. C. J. Van Rijn. 1997. Predation by mites and insects, pp. 25 354. In T. Lewis (ed.), Thrips as crop pests. CAB International, Wallingford, UK. SAS Institute. 2003. SAS System for Windows, version 9.1. SAS Institute, Cary, NC. Schauber, E. M., R. S. Ostfeld, and C. G. Jones. 2004. Type 3 functional response of mice to gypsy moth pupae: is it stabilizing? Oikos 107: 592 602. Seal, D. R., and R. K. Jansson. 1989. Biology and management of corn silk fly, Euxestastigmatis Loew (Diptera: Otitidae), on sweet corn in southern Florida. Proceedings of theFlorida State Ho rticultural Society 102: 370 373. Seal, D.R., and R. K. Jansson. 1993. Oviposition and development of Euxesta stigmatis (Diptera: Otitidae). Environmental Entomology 22: 88 92. Seal, D.R., R. K. Jansson, and K. Bondari. 1995. Bionomics of Euxesta s tigmatis (Diptera: Otitidae) on sweet corn. Environmental Entomology 24: 91 922. Seal, D.R., R. K. Jansson, and K. Bondari. 1996. Abundance and reproduction of Euxesta stigmatis (Diptera: Otitidae) on sweet corn in different environmental conditions. F lorida Entomologist 79: 413 422. Seal, D. R. 2001. Control of the corn silk fly using various insecticides, 2000. Arthropod Management Tests 26: E31. Entomological Society of America, http://www.entsoc.org/ Protected/AMT/AMT26/INDEX. ASP.

PAGE 111

111 Severin, H H. P., and W. J. Hartung. 1912. Will the Mediterranean fruit fly ( Ceratitis capitata Wied.) breed in bananas under artificial and field conditions? Journal of Economic Entomology 6: 443 451. Sigsgaard, L., and P. Esbjerg. 1997. Cage experiments on Orius tantillus predation of Helicoverpa armigera Entomologia Experimentalis et Applicata 82: 311 318. Silvie, P. J., H. P. Aberlenc, C. Duverger, J.M. B renger, R. Cardozo, V. Gomez. 2007. Harmonia axyridis no Paraguai e novos predadores identific ados no cultivo do algodoeiro ( Harmonia axyridis in Paraguay and new predators identified in cotton crop). In proceedings, Simposio de Controle Biologico. 30 June 4 July 2007, Brasilia Brsil. Shrestha, R. M., and M. N. Parajulee. 2004. Functional respo nse of selected cotton arthropod predators to bollworm eggs in the laboratory. Beltwide cotton conferences, Jan 5 9, 2004, San Antonio, T X. Solomon, M.E. 1949. The natural control of animal populations. Journal of Animal Ecology 18: 1 35. Southwood, T. R. E. 1978. Ecological methods. 2 Ed. Chapman & Hall, London. Sterling,W.L. K.M. El Zik and L.T. Wilson. 1989. Biological control of pest populations pp. 159 189 In Integrated Pest Management Systems and Cotton Production. John Wiley and Sons, Ne w York. Stern, V. 1981. Environmental control of insects using trap crops, sanitation, prevention, and harvesting, pp 199 207. In D. Pimentel (ed.) CRC Handbook of Pest Management in Agriculture, Vol. 1. CRC Press, Boca Raton, Florida. Steyskal, G. C 1952. Ulidiinae (Diptera, Otitidae) of Australian regions. Occasional papers of Bernice P. Bishop Museum. Vol. XX 15. Steyskal, G. C. 1961. The genera of Platystoniatidae and Otitidae know to occur in America north of Mexico (Diptera, Acalyptratae ). Annals of Entomological Society of America. 54: 401 410. Steyskal, G. C. 1968. Family Otitida (Ortalidae: including Pterocallidae, Ulidiidae). A Catalogue of the Diptera of the Americas South of the United States. Departmento de Zoologia, Secretari a de Agricultura, Sao Paulo, Brasil. 54: 1 31. Steyskal, G. C. 1971. A new Central American species of Zacompsia Coquillett, with a key to the described species (Diptera: Otitidae). Proceedings of the Entomological Society of Washington 73: 247 248.

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112 Sutherland, W. J. .1983. Aggregation and the ideal free distribution. Journal of Animal Ecology. 52:821 828. Taylor, L. R. 1961 Aggregation, variance and the mean. Nature (London) 189: 732 735. Taylor, L. R. 1984. Assessing and interpreting the spatial distributions of insect populations. Annual Review of Entomology 29: 321 357. Garcia,and E.J.P. Marshall. 2001 hedgerow habitats. Journal of Applied Ecology. 38:100 116. Thompson, J.D. 1975. Towards a predator prey model incorporating age structure. The effects of predator and prey size on predation of Daphnia magna by Ischnura elegans. Journal of Animal Ecology 44: 907 916. T hompson F. C. 2006. Evenhuis, T. Pape, A. C. Pont, and F. C. Thompson [eds]. Biosystematic Database of World Diptera. http://www.sel.barc.usda .gov/Diptera/names/FamClass.htm Tillman, P. G., and J. E. Mulrooney. 2000. Effect of selected insecticides on the natural enemies Coleomegilla maculata and Hippodamia convergens (Coleoptera: Coccinellidae), Geocoris punctipes (Hemiptera: Lygaeidae), and Bracon mellitor Cardiochiles nigriceps and Cotesia marginiventris (Hymenoptera: Braconidae) in cotton. Journal of Economic Entomology 93: 1638 1643. U nigaro, P.A. 1958. Biologla del predator Zelus longipes linneo (Hemiptera: Reduviidae) en el vale Cauca. Revista facultad nacional de agronomia. Medellin. (USDA) U. S. Department of Agriculture. 2011. Vegetable summary 2010. (USDA) U. S. Department of Agriculture. 2010. National Agriculture Statistics Service (NASS). USDA. (USDA) U. S. Department of Agriculture. 2010. Economic Research Service (NASS). USDA. Van Zwaluwenburg, R. H. 1917. Report of the entomologist. Puerto Rico Agriculture Expe riment Station. 31 34.

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113 van den Meiracker, R. A. F., and P. M. J. Ramakers. 1991. Biological control of the western flower thrips Frankliniella occidentalis in sweet pepper with the anthocorid predator Orius insidiosus Mededelingen van de Faculteit Landbouwwetenschappen Universiteit Gent 56: 241 249. Walter, E. V., and G. P. Wene. 1951. Tests of insecticides to control larvae of Euxesta stigmatias and Megaselia scalaris Journal of Economic Entomology 44: 998 999. Way, M. J., and H. F. van Emde n. 2000. Integrated pest management in practice pathwaystoward successful application. Crop Protection 19: 81 103. Wheeler, A. G., Jr., and C. A. Stoops. 1996. Status and spread of the Palearctic lady beetles Hippodamia variegata and Propylea quatuor decimpunctata (Coleoptera: Coccinellidae) in Pennsylvania, 1993 1995. Entomological News 107: 291 298. Wiedenmann R N and R J ONeil 1 99 1. Searching behavior and time budgets of the predator Podisus maculiventris Entomologia Experimentalis et Applica ta 6: 83 93 Wilson, M. L. 2010. Differential responses of odor mediated predators to density and distribution characteristics of prey patches. 95 th ESA annual meeting. 1 st August to 6 th August. Pittsburgh, P A Wulp, F. M. 1903. Biologia centrali amer icana Insecta, Diptera. pp 396 399. Vol. III. http://books.google.com/books?id=lQlQAAAAYAAJ&pg=PA399&lpg=PA399&dq=euxest a+stigmatias+metallic+green&source=bl&ots=rrSkW7ghAS&sig=6uadrqmjlphoHIC63ta5 mQts6eE&hl=en&ei=z7kKTrH2BsWEtgf2hax3&s a=X&oi=book_result&ct=result&resnu m=3&ved=0CCMQ6AEwAg#v=onepage&q=euxesta%20stigmatias%20&f=false Xiao, C. L., J. J. Hao and K. V. Subbarao. 1997. Spatial patterns of microsc lerotia of Verticillium dahliae in soil and Verticillium wilt of cauliflower. Phytopathology 87 :325 331. Yoon, J. S., M. T. Mathew, and R. E. Holman. 1983. Biology of Euxesta quaternaria Loew (Diptera: Otitidae). E ntomological News 94: 122 126

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114 BI OGRAPHICAL SKETCH Megha Kalsi was born and brought up in New Delhi, India. She received her Ba stimation of total serum IgE and molecular c haracterization of fungal antigens at Allergy and Immunology Section, Institute of Genomics & Integrativ e B iology (CSIR), Delhi under the guidance of Dr. A. B. Singh After completing her graduated from. She worked there for six months (2006 2007). In spring 2009, she was enro degree in entomology under the supervision of Dr. Dakhshina R. Seal. Her research focused on potential predators of corn infesting Ulidiidae in sweet corn filed, Homestead: a report on their distribu tion and functional response. She found two predators feeding on different life stages of these program, she received various travel grants and prizes for student paper competitions. In fall 2011, she will began her PhD program at University of Kentucky, Lexington. She