Management of western bean cutworm Striacosta albicosta (Lepidoptera: Noctuidae) and mycotoxins in Ontario maize by Jocelyn Leigh Smith A Thesis presented to The University of Guelph In partial fulfilment of requirements for the degree of Doctor of Philosophy in Plant Agriculture Guelph, Ontario, Canada © Jocelyn L. Smith, August, 2017 ABSTRACT Management of western bean cutworm Striacosta albicosta (Lepidoptera: Noctuidae) and mycotoxins in Ontario maize Jocelyn Leigh Smith Advisors: University of Guelph, 2017 Dr. A. W. Schaafsma Dr. R. H. Hallett Western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a pest of maize, Zea mays (L.), that has recently established in Ontario, Canada following a range expansion from the western United States. In addition to yield loss, ear feeding by S. albicosta was expected to exacerbate infection of mycotoxigenic fungi in maize grain, especially in southern Ontario where environmental conditions frequently favour infection of maize by Fusarium spp. The objective of this research was to determine effective management strategies for S. albicosta in Ontario. Specifically, the efficacy of Cry1F Bacillus thuringiensis (Bt) transgenic maize was evaluated for control of S. albicosta injury in field experiments from 2011- 2015, and the susceptibility of Ontario field-collected S. albicosta to Cry1F was investigated using laboratory concentration-response bioassays. Non-Bt and Bt (Cry1F and Vip3A × Cry1Ab) maize hybrids in combination with insecticides and fungicides were evaluated for control of S. albicosta injury and accumulation of mycotoxins, particularly, deoxynivalenol (DON), under natural field infestation conditions from 2011-2014. The most effective application timing of pesticides was also investigated. Lastly, the relationship between S. albicosta injury and DON accumulation in maize was investigated based on field experiments in 2012-2014. A simple calculation for estimating the risk of F. graminearum infection during the silking and insect feeding periods was used to develop parameters to describe the relationship between S. albicosta injury and DON accumulation using multiple regression analysis. The results of this research provide evidence for field-evolved resistance to Cry1F within Ontario populations of S. albicosta and confirm the lack of efficacy of Cry1F-expressing hybrids for control of S. albicosta. Excellent control of S. albicosta injury was achieved with the Vip3A event and control of non-Bt and Cry1F maize was improved with insecticide application; however, low levels of DON were observed regardless of Bt event. A combined application of insecticide and fungicide at the full silking stage is recommended for maize hybrids lacking tolerance to F. graminearum infection. Lastly, these results confirm that injury by S. albicosta can increase the risk of DON accumulation in maize grain in Ontario; however, hybrid tolerance to F. graminearum and environmental conditions are predominant factors in DON accumulation. iv PREFACE The presented dissertation is organized as a series of manuscripts accepted for publication or to be submitted for publication in peer-reviewed scientific journals. Each manuscript was written by Jocelyn L. Smith. The reference for the first accepted publication included here as Chapter 2 is listed below: Smith, J.L., Lepping, M. D., Rule, D. M, Farhan, Y., Schaafsma, A.W. Evidence for field- evolved resistance of Striacosta albicosta (Lepidoptera: Noctuidae) to Cry1F Bacillus thuringiensis protein and transgenic corn hybrids in Ontario, Canada. Journal of Economic Entomology. (in press). v ACKNOWLEDGMENTS I first want to thank my advisor, Art Schaafsma, for the many opportunities he has provided me over the years that have helped me to learn and improve as a researcher. I truly appreciate his motivation and enthusiasm for our work, and the guidance and support that he provides for myself and our research team. I also want to thank Tracey Baute and Dr. Chris DiFonzo who I consider mentors. I will always remember that Tracey was the first person to call me an entomologist when I was her summer student, and how surprisingly validating that was. Both Tracey and Chris have been so inclusive, encouraging, not to mention, fun to work with, and I am inspired by all that they accomplish. I am grateful to have Todd Phibbs, Jennifer Bruggeman, and Yasmin Farhan as tirelessly supportive colleagues and friends who assisted with my field and laboratory research in the past, present, and hopefully, future. I also thank Jennifer Bruggeman, Yasmin Farhan, and Jacqueline Verhallen for their efforts in rearing western bean cutworm. I am thankful for the cooperation of the growers who allowed research experiments to be conducted on their land. I thank Karla Jackson of Weather Innovations Consulting LP (Chatham, ON) for providing weather data from the field experiment sites. I sincerely thank my advisory committee: Dr. Christina DiFonzo, Michigan State University, Dr. Rebecca Hallett, and Chris Gillard, University of Guelph, for their guidance, suggestions and patience. I also thank my friends and co-authors: Dr. Victor Limay-Rios and Dr. David Hooker, University of Guelph, for collaborating with me on this research and participating in many helpful brain-storming sessions. Useful critical reviews of these manuscripts by Dr. vi Nicholas Storer and Dr. Gregory Bradfisch (Dow AgroSciences LLC), Dr. Clinton Pilcher and Dr. Andre Crespo (Dupont Pioneer) are also appreciated. I thank the following sponsors of this research: the Ontario Ministry of Agriculture, Food, and Rural Affairs-University of Guelph Partnership, Agriculture and Agri-Food Canada’s Canadian Agricultural Adaptation Program (CAAP) which is delivered by the Agricultural Adaptation Council in Ontario, and the Grain Farmers of Ontario. Funding, seeds, and pesticides were provided by Pioneer Hi-Bred International Inc., Syngenta Crop Protection Canada Inc., Bayer CropScience Inc., and E.I. DuPont Canada Company. Finally, I am extremely grateful to my many family members and friends who have encouraged and supported me over the years. There are almost too many to name, but it means the world to me that they all believed in me and are proud of me. I remember saying in my late high school, early undergraduate days that I wanted to do something in agricultural research for a career. At the time, I didn’t exactly know what that meant, but I think it has come to be. I have enjoyed (almost) everything so far in my career, and I wouldn’t want to do anything else. It has been invigorating to become friends and colleagues with so many people in this field of work in the U.S., Canada, and elsewhere. I also want to acknowledge my many wonderful colleagues at the Ridgetown Campus who have been very supportive and are all working towards the common goal of supporting and improving Ontario agriculture. vii TABLE OF CONTENTS ABSTRACT ............................................................................................................................... ii PREFACE ................................................................................................................................. iv ACKNOWLEDGMENTS ........................................................................................................ v TABLE OF CONTENTS ........................................................................................................ vii LIST OF TABLES .................................................................................................................... x LIST OF FIGURES ............................................................................................................... xiii ABBREVIATIONS ................................................................................................................ xiv CHAPTER 1 INTRODUCTION ........................................................................................... 1 1.1 DISTRIBUTION ............................................................................................................... 1 1.2 LIFE HISTORY ................................................................................................................ 3 1.3 HOST RANGE .................................................................................................................. 6 1.4 PEST STATUS IN MAIZE ............................................................................................... 6 1.5 INSECT INJURY AND MYCOTOXINS IN MAIZE ...................................................... 7 1.6 MANAGEMENT IN MAIZE ........................................................................................... 9 1.6.1 Cultural Control .......................................................................................................... 9 1.6.2 Biological Control ..................................................................................................... 10 1.6.3 Chemical Control ...................................................................................................... 11 1.6.4 Monitoring ................................................................................................................ 12 1.6.5 Transgenic Maize ...................................................................................................... 14 1.7 CONCLUSIONS AND RESEARCH OBJECTIVES ..................................................... 16 CHAPTER 2 EVIDENCE FOR FIELD-EVOLVED RESISTANCE OF STRIACOSTA ALBICOSTA (LEPIDOPTERA: NOCTUIDAE)