UNIVERSITY OF CALIFORNIA RIVERSIDE Management Strategies for the Potato Psyllid in California A Dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Entomology by Casey Douglas Butler August 2011 Dissertation Committee: Dr. John T. Trumble, Chairperson Dr. Timothy D. Paine Dr. Richard Stouthamer Copyright by Casey Douglas Butler 2011 The Dissertation of Casey Douglas Butler is approved: _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ Committee Chairperson University of California, Riverside Acknowledgements I would like to thank most of all my major advisor, Dr. John T. Trumble, for his guidance and support. I will always be thankful and indebted for this opportunity he has given me to pursue this degree under his direction. I would also like to thank Dr. Timothy Paine and Dr. Richard Stouthamer for always having an open door for me, and being there whenever I needed help. Special thanks also go out to the many members of the Trumble lab that have helped over the years with colony rearing, experiments, and reviews of manuscripts. These individuals are Bill Carson, Greg Kund, Kristen Hladun, Chrissy Mogren, John Diaz-Montano, Beatriz Vindiola, Natalie Solares, Lindsay Johnson, Kris Gilbert, Sam Gilbert, Nellie Murillo, and Nicole Drew. I would also like to acknowledge the help with the molecular work from Jennifer Noe, Lupe Heldoorn, Esteban Rodriguez, and Justin Justus at the USDA-ARS National Clonal Germplasm Repository for Citrus and Dates. I also want to thank my many collaborators. I would like to thank Dr. Keremane Manjunath and Dr. Richard Lee at the USDA-ARS National Clonal Germplasm Repository for Citrus and Dates for their help with the molecular work, and Dr. Frank Byrne at the University of California, Riverside, for his help with the ELISA to determine the quantity of imidacloprid residues in potato leaf tissue. Their help was used to publish an article in the Journal of Economic Entomology (2011), 104: 586-594. I would like to thank Dr. Richard Novy (USDA-ARS, Small Grains and Potato Germplasm Research Unit) and Dr. J. Creighton Miller (Texas A&M University) for the development of the potato germplasm used in the study to assess the effects of potentially resistant breeding iv clones and varieties on adult potato psyllid behaviors and disease transmission. Drs. Manjuanth and Lee are acknowledged for their help with this work as well. This article was published in the journal of Crop Protection (2011), 30: 1233-1238. I also want to thank Dr. Greg Walker (University of California, Riverside) for teaching me the electrical penetration graph technique. Special thanks also to Thomas Prentice (University of California, Riverside), Dr. Christiane Weirauch (University of California, Riverside), Dr. Douglas Yanega (University of California, Riverside) and Dr. Robert Zuparko (California Academy of Sciences) for identifications of natural enemies with the biological control work. I want to thank Brent Lunt (Agri-Empire Corp.), Richard Martinez (Deardorff Family Farms), Phil McGrath (McGrath Family Farms), and Edward Shell (Sun World International, LLC) for permission to sample crop plants for potato psyllids and natural enemies. I want to thank Dr. Joseph Munyaneza (USDA-ARS) who initially obtained the potato psyllids for this research. These studies were supported in part by the following grants: USDA-SCRI (2009- 34381-20036), USDA-RAMP (2009-51101-05892), and USDA-PMAP (2009-34381- 20036) programs, and the Robert and Peggy van den Bosch Memorial Scholarship. I am also grateful to family and friends for their support and encouragement. Thanks for the support from Dr. Clifford Sadof and Dr. Steve Yaninek from Purdue University, and thanks to Dr. Robert O’Neil who convinced me to go on for my doctoral degree. Last, but in no way least, I want to give a very big thanks to my wife, Jennifer Butler, for her love and support while pursuing this degree. v Dedications To my wife, To my family, To the memory of Robert J. O’Neil vi ABSTRACT OF THE DISSERTATION Management Strategies for the Potato Psyllid in California by Casey Douglas Butler Doctor of Philosophy, Graduate Program in Entomology University of California, Riverside, August 2011 Professor John T. Trumble, Chairperson The potato/tomato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is a major pest of solanaceous crops. This pest causes yield loss by direct feeding on crop plants and by transmitting a bacterial pathogen known as Candidatus Liberibacter psyllaurous (a. k. a. Ca. L. solanacearum). The goal of my research is to improve pest management against this pest in potatoes by integrating sampling, insecticides, use of resistant varieties, and biological control. Sampling plans are essential part of integrated pest management (IPM). From my research on potatoes, I determined the most efficient sampling unit, and that this pest has an aggregated distribution in the field. Binomial sequential sampling plans were developed for the potato psyllid. Current pest management practices in the USA rely on the intensive use of broad-spectrum insecticides to control the potato psyllid to lower disease incidences and increase yields. I evaluated five insecticides in the laboratory. All insecticides tested significantly reduced probing durations and increased the amount of time adult psyllids spent off the leaflets compared to untreated controls suggesting that vii these chemicals may be deterrents to feeding as well as repellents. Additionally, I further tested the effects of imidacloprid on potato psyllid feeding behavior using a direct current electrical penetration graph technique. Host plant resistance can be an integral component of an integrated approach for the management of arthropod pests. I tested the effects of potato germplasm from 22 genotypes on adult potato psyllid behavioral responses for possible antixenosis and determined if specific breeding clones or varieties can decrease transmission of Ca. L. psyllaurous. Another assessment that should be made in an IPM program is the potential role of natural enemies in controlling pests. Through two years of field studies (2009- 2010) at four different sites and laboratory feeding tests, I have identified Orius tristicolor (White) (Hemiptera: Anthocoridae), Geocoris pallens Stal (Hemiptera: Geocoridae), Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae), and the parasitoid Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) as key natural enemies of the potato psyllid in southern California potatoes, tomatoes, and bell peppers. I discuss how this information can be used in an integrated pest management program for the potato psyllid. viii TABLE OF CONTENTS CHAPTER 1 Introduction and literature review .................................................................…1 Bactericera cockerelli (Sulc) .................................................................................................…4 Psyllid Yellows ........................................................................................................................11 Zebra Chip Disease ..................................................................................................................14 Management Strategies ............................................................................................................18 References ................................................................................................................................30 CHAPTER 2 Spatial dispersion and binomial sequential sampling for the potato psyllid (Hemiptera: Triozidae) on potato ............................................................................................43 Abstract ....................................................................................................................................44 Introduction ..............................................................................................................................45 Materials and Methods .............................................................................................................46 Results ......................................................................................................................................51 Discussion ................................................................................................................................54 References ................................................................................................................................59 CHAPTER 3 Effects of insecticides on behavior of adult Bactericera cockerelli (Hemiptera: Triozidae) and transmission of Candidatus Liberibacter psyllaurous ................62 Abstract ....................................................................................................................................63 Introduction ..............................................................................................................................64 ix Materials and Methods .............................................................................................................68 Results ......................................................................................................................................74 Discussion ................................................................................................................................82