University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2019 Evaluation of candidate pheromone blends for mating disruption of the invasive swede midge (Contarinia nasturtii) Elisabeth Ann Hodgdon University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Agriculture Commons, and the Entomology Commons Recommended Citation Hodgdon, Elisabeth Ann, "Evaluation of candidate pheromone blends for mating disruption of the invasive swede midge (Contarinia nasturtii)" (2019). Graduate College Dissertations and Theses. 1063. https://scholarworks.uvm.edu/graddis/1063 This Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. EVALUATION OF CANDIDATE PHEROMONE BLENDS FOR MATING DISRUPTION OF THE INVASIVE SWEDE MIDGE (CONTARINIA NASTURTII ) A Dissertation Presented by Elisabeth Ann Hodgdon to The Faculty of the Graduate College of The University of Vermont In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Specializing in Plant and Soil Science May, 2019 Defense Date: March 22, 2019 Dissertation Examination Committee: Yolanda H. Chen, Ph.D., Advisor Kimberly F. Wallin, Ph.D., Chairperson David S. Conner, Ph.D. Scott C. Merrill, Ph.D. Cynthia J. Forehand, Ph.D., Dean of the Graduate College ABSTRACT Swede midge ( Contarinia nasturtii , Diptera: Cecidomyiidae) is a small invasive fly that is currently threatening Brassica vegetable and oilseed production in the Northeastern U.S. and Canada. Larvae feed on plant meristems, resulting in deformed leaves, stems, and heads. Extremely low damage thresholds for heading Brassica vegetables, multiple overlapping generations, and lack of effective organic insecticide options present serious challenges for managing this pest. Pheromone mating disruption (PMD), which involves confusing male insects with unnaturally large doses of sex pheromones, is particularly promising for swede midge management because it prevents mating and subsequent oviposition. One major challenge to PMD for swede midge management is that the chiral female pheromone blend, a 1:2:0.02 blend of (2 S, 9 S)- diacetoxyundecane, (2 S, 10 S)-diacetoxyundecane and ( S)-2-acetoxyundecane, is expensive to synthesize due to the structural complexity of the compounds. Here, we explored three ways to reduce the cost of swede midge PMD: the use of lower-cost racemic pheromones containing all possible stereoisomers, single-component blends, and the possibility of using timed pheromone dispensers by testing for diel patterns of midge reproductive behavior. Although we found that males were not attracted to blends containing the racemic stereoisomers of the main pheromone component, (2 S, 10 S)-diacetoxyundecane, racemic blends functioned equally as well as chiral blends in confusing males and altering female behavior in PMD systems. We observed 95% and 87% reductions in males caught in monitoring traps in three-component chiral and racemic PMD plots of broccoli, respectively. In addition to confusing males, we also found that females altered their reproductive behavior in response to both chiral and racemic pheromones. Females released pheromones more frequently when exposed to three-component chiral and racemic blends, and were less likely to mate afterward. Single-pheromone treatments containing either chiral or racemic 2,10-diacetoxyundecane neither confused males nor influenced female behavior. We identified a total of eight hours during the day and night when midges do not exhibit mate-seeking behavior, during which programmable PMD dispensers could be turned off to save pheromone inputs. We found that up to 81% of females released pheromones to attract males for mating in the early morning shortly after dawn. Most females emerged in the morning as well, releasing pheromones soon after eclosing. Because midges are receptive to mates shortly after emergence, they may mate at their emergence site. Overall, we found relatively high levels of crop damage in our pheromone-treated plots, likely due to the migration of mated females into our plots. If midges mate at emergence sites, rotation of Brassica vegetable crops may result in overwintered midges emerging in fields where host plants are not currently grown. Further research is needed to determine where midges mate in order to determine where to install PMD dispensers. CITATIONS Material from this dissertation has been accepted for publication in The Canadian Entomologist on January 17, 2019 in the following form: Hodgdon E.A., Hallett R.H., Stratton C.A., Chen Y.H.. (2018). Diel Patterns of Emergence and Reproductive Behaviour in the Invasive Swede Midge (Diptera: Cecidomyiidae). The Canadian Entomologist. AND Material from this dissertation has been submitted for publication to the Journal of Chemical Ecology on February 5, 2019 in the following form: Hodgdon, E.A., Hallett R.H., Stratton C.A., Chen Y.H.. (2019). Racemic Pheromone Blends Disrupt Mate Location in the Invasive Swede Midge ( Contarinia nasturtii ). Journal of Chemical Ecology. ii ACKNOWLEDGEMENTS I express a great deal of gratitude to my advisor, Dr. Yolanda Chen, for her mentorship over the past four years. I can attribute a great deal of my growth as a scientist to Yolanda, who taught me the value of critical and original thinking in research. I also thank my committee members, Dr. David Conner, Dr. Rebecca Hallett, Dr. Scott Merrill, and Dr. Kimberly Wallin for helping shape my research projects and providing insightful advice during my Ph.D. program. I am grateful for the companionship of my labmates in the Insect Agroecology and Evolution Lab. Chase, Kristian, Jorge, and Andrea, I appreciate your friendship and support over the years. To the Hallett Lab at the University of Guelph, thank you for welcoming me into your lab and helping me through 24-hour experiments and tedious field work every summer. I also thank Jamie Heal, the UVM Greenhouse staff, Pfenning’s and Elora Research Station farm staff, and countless student research assistants for all their help with my experiments. I thank Amy Saenger for her patience and last-minute assistance formatting this dissertation. Last but not least, I thank my soon-to-be husband, Ben, and my family for their continuous support for my studies. One of my fondest memories during my Ph.D. is when Ben helped me observe midge mating at 5 am before he went to work. To my dad, Andy, the hardest worker I know, I owe my work ethic and love of insects. To my mom, Nadine, I owe my attention to detail and love of learning. Thank you. iii TABLE OF CONTENTS CITATIONS…………………………………………………………………………… ii ACKNOWLEDGEMENTS…………………………………………………………...iii LIST OF TABLES…………………………………………………………………... viii LIST OF FIGURES……………………………………………………………………ix CHAPTER 1: INTRODUCTION…………………………………………………….. 1 1.1 Introduction ................................................................................................................ 1 1.1.2 Pheromone Mating Disruption .......................................................................................... 1 1.1.3 Mating Disruption in Annual Systems .............................................................................. 1 1.2 The Invasive Swede Midge ........................................................................................ 3 1.2.1 Life Cycle and Biology ..................................................................................................... 3 1.2.2 Management ...................................................................................................................... 5 1.3 Opportunities for Economical Mating Disruption of Swede Midge .......................... 6 1.3.1 Racemic Pheromone Blends.............................................................................................. 7 1.3.2 Efficient Pheromone Application ...................................................................................... 8 1.4 Research Objectives ................................................................................................... 9 1.5 References cited ....................................................................................................... 11 CHAPTER 2: RACEMIC PHEROMONE BLENDS DISRUPT MATE LOCATION IN THE INVASIVE SWEDE MIDGE ( CONTARINIA NASTURTII )………………………………………………………………………….. 18 2.1 Acknowledgements .................................................................................................. 19 2.2 Abstract .................................................................................................................... 20 2.3 Introduction .............................................................................................................. 21 2.4 Methods and Materials ............................................................................................. 25 2.4.1 Swede Midge Colony Rearing ........................................................................................ 25 2.4.2 Test Insects ...................................................................................................................... 26 2.4.3 Swede Midge Pheromone................................................................................................ 26 iv 2.4.4 Male Dose-Response to Chiral Pheromone ...................................................................