COMPARISONS BETWEEN CONVENTIONAL AND SUSTAINABLE EGGPLANT (Solanum melongena L.) PRODUCTION SYSTEMS by Kathryn Estelle Brunson (Under the direction of SHARAD C. PHATAK) ABSTRACT The growing consumer and environmental concerns over the use of pesticides and nitrogen based fertilizers in agriculture has emphasized the need for more information concerning the reduction of these inputs on a commercial scale. Sustainable agriculture philosophy promotes using beneficial insects and legume cover crops as a means to do so. However, information is limited as to how sustainability can be conducted on a commercial crop such as eggplant, and still be economically feasible. Field trials were conducted during 1991-93 at four locations comparing sustainable and conventional eggplant production practices. The four sites differed by soil type and cropping histories. Overwintering cover crops of crimson and subterranean clovers were used to help maintain soil fertility and populations of beneficial insects in the sustainable production system. No pesticides were used throughout the study. Velvetbean (Mucuna deeringiana L.) was incorporated into the rotation following eggplant in 1992-93 to help suppress populations of southern root-knot nematode (Meloidogyne incognita Koford and White). The conventional production system differed in that cereal rye was the plow-down cover crop and recommended fertilizer and pesticide practices were followed. Highest marketable eggplant yields were in the conventional system for each location and year. Crimson clover generally had the better yields compared to the subterranean clover but there were differences between locations and year. Regression analysis showed conventionally grown eggplant fruited earlier but that crimson clover had the potential to "catch" up in later harvests. Pest and beneficial insects populations were assessed by visual and shake sampling methods to determine differences among production systems. Shake sampling of eggplant foliage resulted in more species being recovered than did visual inspection. Weed populations differed according to location. Each location appeared to have had its own distinctive weed species. Overall percent weed cover was less in the sustainable compared to the conventional where nutsedge was the predominant problem. Use of velvetbean in the rotation in 1993 seemed to have an effect on populations of southern root-knot nematode incurred in the sustainable production. Levels were generally reduced in most locations while levels either stayed the same or increased in the conventional system that had been treated with a nematicide. Root gall and root disease severity ratings of eggplant were not significantly different between systems. The economic comparisons seemed to indicate that production costs and net returns for the conventional system were higher than for the sustainable, but sustainable yields were lower. INDEX WORDS: Eggplant, Solanum melongena L., Sustainable Production, Conventional Production, Beneficial Insects, Insect Pests, Vegetable Production, Weeds, Soil Borne Diseases, Plant Parasitic Nematodes, Risk Assessment, Agricultural Economics, Economic Feasibility COMPARISONS BETWEEN CONVENTIONAL AND SUSTAINABLE EGGPLANT (Solanum melongena L.) PRODUCTION SYSTEMS by KATHRYN ESTELLE BRUNSON B.S.A. The University of Georgia 1982 M.S. The University of Georgia 1991 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2002 © 2002 Kathryn Estelle Brunson All Rights Reserved COMPARISONS BETWEEN CONVENTIONAL AND SUSTAINABLE EGGPLANT (Solanum melongena L.) PRODUCTION SYSTEMS by KATHRYN ESTELLE BRUNSON Approved: Major Professor: Sharad C. Phatak Committee: Albert K. Culbreath Juan Carlos Diaz-Perez John R. Ruberson Michael E. Wetzstein Electronic Version Approved: Gordhan L. Patel Dean of the Graduate School The University of Georgia May 2002 DEDICATION To All Who Helped Me Complete This Part of the Journey iv ACKNOWLEDGMENTS The author wishes to express her sincere appreciation to her major professor, Dr. Sharad C. Phatak, for his continual support, guidance and encouragement throughout this endeavor. His humor and enthusiasm in the face of adversity I will always remember. I also wish to express my deep appreciation to the members of my graduate committee, Dr. Albert K. Culbreath, Dr. Juan Carlos Diaz-Perez, Dr. John R. Ruberson and Dr. Michael E. Wetzstein for their counsel and direction. Gratitude is also expressed to Dr. Phatak's supporting staff, especially Anthony Bateman and the late Jimmy Hornbuckle, for helping me progress through this work. I also wish to express deep gratitude to Dr. Bob Stark of the University of Arkansas-Monticello for his assistance in preparing the economic budgets. Lastly, I thank Kathy Mullinix, Kim Giddens and Richard Layton for their continued help and friendship throughout these past years. Financial support for this work was provided through the Southern Region IPM Program of the Cooperative State Research Service, USDA, Grant # 89-34103-4257 and other funds allocated to the Coastal Plain Experiment Station, College of Agriculture and Environmental Sciences, University of Georgia, Tifton, Georgia. v TABLE OF CONTENTS Page ACKNOWLEDGMENTS .................................................v LIST OF TABLES ...................................................... ix LIST OF FIGURES ..................................................... xii CHAPTER 1 LITERATURE REVIEW .................................................1 Introduction .......................................................2 Sustainable Production ...............................................4 Conventional Production ............................................32 Economic Considerations of Sustainable and Conventional Production ..........34 Literature Cited ...................................................37 2 EFFECT OF LOCATION AND PRODUCTION SYSTEM ON CONVENTIONAL AND SUSTAINABLE EGGPLANT YIELDS ...............47 Abstract .........................................................48 Introduction ......................................................48 Materials and Methods ..............................................49 Results ..........................................................54 Discussion .......................................................60 Conclusion .......................................................63 Literature Cited ...................................................65 vi 3 INFLUENCE OF LOCATION AND PRODUCTION SYSTEM ON SEASONAL INSECT POPULATIONS, WEEDS, NEMATODES, ROOT DISEASE AND PLANT STAND IN CONVENTIONAL AND SUSTAINABLE EGGPLANT ...........................................87 Abstract .........................................................88 Introduction ......................................................89 Materials and Methods ..............................................92 Results ..........................................................94 Discussion ......................................................102 Conclusion ......................................................110 Literature Cited ..................................................113 4 ECONOMIC COMPARISONS OF ALTERNATIVE AND CONVENTIONAL PRODUCTION TECHNOLOGIES FOR EGGPLANT IN SOUTHERN GEORGIA 132 Abstract ........................................................133 Introduction .....................................................133 Materials and Methods .............................................134 Results and Discussion .............................................138 Conclusion ......................................................142 Literature Cited ..................................................142 5 CONCLUSIONS ....................................................156 vii LIST OF TABLES TABLE Page CHAPTER 2 2.1 Influence of location and production system on marketable eggplant yields. ..........................................................66 2.2 Influence of location and production system on unmarketable eggplant yields. ....................................................67 2.3 Effect of location and production system on eggplant cull yields ................68 2.4 Eggplant rot yields influenced by location and production system ...............69 2.5 Eggplant insect damage influenced by location and production system ..........................................................70 CHAPTER 3 3.1 Effect of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and Coccinellids recovered from visual inspections 1992 .......................117 viii 3.2 Effect of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and Coccinellids recovered from visual inspections 1993 .......................118 3.3 Influence of location and production system on seasonal insect populations of Geocoris, Lygus, Colorado Potato Beetle and Coccinellids recovered from 1992 shake sampling. ........................119 3.4 Influence of location and production system effects on seasonal insect populations of Aphids, Stinkbugs, Loopers, Thrips, and Other Hoppers recovered from 1992 shake sampling. ..........................120 3.5 Influence of sustainable and conventional production practices on weeds. ......................................................121 3.6 Visual weed evaluations in sustainable and conventional eggplant production from the Horticulture Farm.