Epidemiology and Disease Management of Stewart's Disease of Corn in Iowa Paul David Esker Iowa State University

Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 2005 Epidemiology and disease management of Stewart's disease of corn in Iowa Paul David Esker Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agriculture Commons, and the Plant Pathology Commons Recommended Citation Esker, Paul David, "Epidemiology and disease management of Stewart's disease of corn in Iowa " (2005). Retrospective Theses and Dissertations. 1727. https://lib.dr.iastate.edu/rtd/1727 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Epidemiology and disease management of Stewart's disease of corn in Iowa by Paul David Esker A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Co-majors: Plant Pathology; Statistics Program of Study Committee: Philip M. Dixon, Co-major Professor Forrest W. Nutter, Jr., Co-major Professor Charles C. Block Petrutza C. Caragea Mark L. Gleason S. Elwynn Taylor Iowa State University Ames, Iowa 2005 UMI Number: 3200414 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. UMI UMI Microform 3200414 Copyright 2006 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 ii Graduate College Iowa State University This is to certify that the doctoral dissertation of Paul David Esker has met the thesis requirements of Iowa State University Signature was redacted for privacy. Co-major Professor Signature was redacted for privacy. Co-major Professor Signature was redacted for privacy. For the Co-major Program Signature was redacted for privacy. For the Co-major Program Ill TABLE OF CONTENTS ACKNOWLEDGMENTS CHAPTER 1. INTRODUCTION AND JUSTIFICATION 1 Thesis Organization 1 Literature Review 1 Justification 28 References 32 CHAPTER 2. TRAP HEIGHT AND ORIENTATION OF YELLOW STICKY CARDS AFFECT CAPTURE OF CHAETOCNEMA PULICARIA (COLEOPTERA: CHRYS OMELID AE) 41 Abstract 41 Introduction 42 Material and Methods 44 Results and Discussion 46 Acknowledgements 50 References 50 Tables 53 CHAPTER 3. EFFECTS OF PLANTING DATE AND SEED INSECTICIDES ON THE REDUCTION OF STEWART'S DISEASE OF CORN IN IOWA 56 Abstract 56 Introduction 57 Material and Methods 62 Results 68 Discussion 73 Acknowledgements 79 References 80 Tables 86 Figures 94 CHAPTER 4. COMPARISON OF THE STEVENS-BOEWE AND IOWA STATE METHOD FOR STEWART'S DISEASE FORECASTING IN IOWA 100 Abstract 100 Introduction 101 Material and Methods 106 Results 110 Discussion 112 Acknowledgements 116 iv References 116 Tables 122 Figures 127 CHAPTER 5. IMPROVED FORECASTING FOR STEWART'S DISEASE OF CORN IN IOWA USING LOGISTIC REGRESSION 129 Abstract 129 Introduction 130 Material and Methods 135 Results 142 Discussion 147 Acknowledgments 152 References 152 Tables 157 Figures 171 CHAPTER 6. GENERAL CONCLUSIONS 175 V ACKNOWLEDGEMENTS Where to begin? The time and effort put forth on this thesis was not without the support of many. First, to my family, I owe you all many thanks. I am sure that at times it seemed like I would never finish, but your support never diminished. Second, to Adriana Murillo-Williams, who has been with me through this entire process. Whether it was regarding my coursework, exams, or thesis writing, your love and support has never wavered. I cannot thank you enough. Furthermore, I must thank my co-advisors, Dr. Philip Dixon and Dr. Forrest Nutter, Jr. You have provided me many opportunities to evolve, both as a researcher and teacher. I would also like to thank Drs. Dean Isaacson and Mark Kaiser, who provided for me the opportunity, as well as the financial support to be a VIGRE Fellow. Also, I need to thank the different funding agencies that provided financial support of research on Stewart's disease and John Harri at the Iowa Department of Agriculture and Land Stewardship (Des Moines, IA) who provided access to the corn inspection data necessary for much of my research. Finally, there are many friends and colleagues who I also need to think. This includes local, national, and international contacts, as well as those working in Plant Pathology and Statistics. To try to name everyone would do an injustice, as I know that I would forget someone. I consider you all my friends and I wish all the best of luck in your endeavors. 1 CHAPTER 1. Introduction and Justification Thesis Organization This thesis is organized into six chapters. Chapter 1 is the introduction and research justification. Chapter 2 is a published journal manuscript. Chapter 3 is ajournai manuscript focusing on Stewart's disease field research conducted in 2002 and 2003. Chapters 4 and 5 are journal papers that focus on forecasting for Stewart's disease of com. Finally, chapter 6 is a general conclusions and discussion chapter. References are provided at the end of each chapter and are specific to that chapter. Literature Review Disease Symptoms and Losses Stewart's disease, caused by the bacterium Pantoea stewartii subsp. stewartii (syn. Erwinia stewartii), primarily affects com {Zea mays) during two crop periods each growing season: the early season seedling wilt phase and the late leaf blight phase (Stewart 1897; Smith 1914; Pepper 1967; Mergaert et al. 1993). Symptoms of Stewart's disease have been previously described in numerous publications (Stewart 1897; Smith 1914; Rand and Cash 1933; Ivanoff 1933; Frutchey 1936; Pepper 1967; Munkvold 2001). Early symptoms during the wilt phase typically include linear, water-soaked lesions that originate from the site of corn flea beetle feeding scars. These lesions expand and coalesce resulting in severe plant stunting and wilting (Dill 1979; Pepper 1967). It is during this phase that direct plant losses occur as a result of seedling death. Pantoea stewartii may also invade the vascular bundles; 2 this invasion is identifiable by yellow, bacterial ooze when the vascular bundles are cut (Stewart 1897; Rand and Cash 1933; Pepper 1967; Munkvold 2001). The wilt phase of Stewart's disease may sometimes be mistaken for several abiotic stresses, including drought damage, nutritional deficiency, and insect feeding. The late leaf blight phase of Stewart's disease can be observed beginning in late July to August, and may become more severe as the rest of the growing season progresses. The early symptoms of the late leaf blight phase occur at the feeding sites of corn flea beetles, thereby facilitating the entry of P. stewartii into the corn plant (Pepper 1967; Dill 1979). Following entry, the bacterium will multiply within the xylem and linear, yellowish, water- soaked lesions originating from the sites of corn flea beetle feeding scars will develop. These lesions will elongate along the corn leaf veins and may cause the eventual blighting of the entire corn leaf and plant. Economic Importance of Stewart's Disease Stewart's disease of corn is an economically important disease in both the seed and sweet corn industries in the US (Stewart 1897; Pepper 1967; Suparyono and Pataky 1989; Pataky et al. 1990; McGee 1995; Pataky et al. 1995). In Iowa, seed corn production is adversely affected by the mere presence of Stewart's disease in seed com fields due to zero tolerance phytosanitary regulations that limit the exportation of seed from fields infected with Stewart's disease (Pepper 1967; McGee 1995). Stewart's disease has been reported to occur in most com growing regions of the United States, and has also been found in other com production regions of the world, including: Central America, Europe, the former USSR, and China (Pepper 1967). Since seed com inspections began in Iowa in 1972, the prevalence of Stewart's disease has been sporadic, however, from 1994 to 2000, the prevalence of 3 Stewart's disease increased exponentially from approximately 3% in 1994 to as high as 58% in 2000 (Nutter et al. 1998; Esker and Nutter 2001; Nutter et al. 2002) (Figure 1). In this thesis, prevalence (%) is defined as the number of inspected seed corn fields found to have Stewart's disease divided, by the total number of seed corn fields inspected x 100. 60 Low prevalence High prevalence Not found 1972197719821987199219972002 Year Figure 1. Prevalence of Stewart's disease in Iowa between 1972 and 2003. Prevalence is defined as the number of fields found to have Stewart's disease divided by the total number of fields inspected each year. The number of seed corn fields inspected each year ranged from less than 100 (in the 1970's) to over 1,300 fields inspected annually (in recent years). In sweet corn production, moderate-to-severe infection of sweet com by P. stewartii can significantly reduce yield and farmer income in susceptible and moderately-susceptible sweet corn hybrids (Pepper 1967; Suparyono and Pataky 1989; Pataky et al. 1990; Pataky et al. 1995). Stewart's disease was first recognized as a major yield-limiting factor in sweet com production during the 1930's, following a dramatic increase in the severity of Stewart's 4 disease on sweet corn in the Northeastern U.S.

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