Field and Bioassay Evaluations of Elm Flea Weevil (Orchestes steppensis Korotyaev) Adult Feeding Preference and Larval Mine Presence among New American (Ulmus americana) and Hybrid Elm (Ulmus spp.) Cultivars Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By James Nathan Radl, B.S., B.A. Graduate Program in Entomology The Ohio State University 2018 Thesis Committee David J. Shetlar, Co-Advisor Andrew P. Michel, Co-Advisor Elizabeth Y. Long, Committee Member David S. Gardner, Committee Member Copyright by James Nathan Radl 2018 Abstract Twelve cultivars of commercially available elms (mostly hybrids) from the National Elm Trial and five cultivars of American elms from the USDA Forest Service Northern Research Station were evaluated for both adult and larval feeding damage by the elm flea weevil, Orchestes steppensis (Coleoptera: Curculionidae). O. steppensis is a recent invasive species in North America that damages elm trees by disfiguring leaves with adult pit feeding and larval mining. A summary of the history, biology, and importance of this pest is included as well as some personal observations of populations in Columbus, Ohio. Trials were repeated using several different variables including: location/type of cultivar, type of evaluation (field choice test and bioassay no-choice test), time of year (for field evaluations only), and life stage (adult feeding and larval mines/oviposition). Generally, the results show that adult O. steppensis have a significant preference for certain cultivars over others. Some of the least preferred cultivars by the adult weevils included ‘Accolade,’ ‘Clone D,’ ‘Commendation,’ ‘Danada Charm,’ ‘Patriot,’ and ‘Triumph.’ Only one American elm was used in the trials comparing different commercially available cultivars (‘Valley Forge’), and it was among the least preferred during the field evaluations but, unexpectedly, one of the most preferred during the bioassay. No preference was detected among different cultivars of the American elm, however, these were also minimally fed upon in the field evaluations and heavily ii fed upon in the bioassays. The field evaluations of the larval mines showed that some commercially available cultivars may have more mines, but this is not consistent throughout the season. The adult preference does not appear to be correlated with larval preference. The oviposition bioassay was inconclusive. Evaluations throughout the year show that adult feeding damage increases between May (after the overwintered population has fed) and June (after the newly emerged population has fed). The weevils’ preference rank among cultivars does not appear to change throughout the year, but the later population seems to show a stronger preference for the preferred cultivars than the original population. The results of these evaluations provide growers with information on which elm cultivars are non-preferred or resistant to O. steppensis feeding, and, therefore, which cultivars would require the least amount of insecticide treatment to keep their leaves healthy. iii Dedication For some, it is difficult to trace where their interest in a subject first began. For me, my interest in science began in the sixth grade, and my interest in entomology began in tenth. Both of these were thanks to my middle and high schools’ Science Olympiad program. I want to dedicate this first major written piece of my entomological career to all the dedicated volunteers who make this program a success, both in my hometown of Chardon, and across the nation. Most of all I want to dedicate this thesis to my first Science Olympiad coach and coach in entomology, Dr. Anne Clouser. It is people like you who inspire young kids to become great scientists, and I believe the world will be a better place with a few more scientists in it. Thank you for all your hard work. I will forever strive to inspire others in the same way you inspired me. iv Acknowledgements I first want to thank my advisor, Dave Shetlar, who put off retirement to help one more student find his way in entomology. His patience, willingness to help, and always positive attitude have been continuously appreciated and necessary to guide me through the challenges of my Master’s program. I also wanted to thank my other committee members, Andy Michel, Elizabeth Long, and Dave Gardner, who have also been willing to take time out of their busy schedules to answer my questions and provide guidance on my projects whenever I needed it. Many of my friends and colleagues have also been very helpful throughout my program. Tae Lee, Mike McFarland, Alex Tyrpak, Tyler Eaton, my wife Kara, and others have been willing to drop what they are doing to join me hunting for weevils, help me with my stats, or guide me on my genetics project. This help is much appreciated and will be remembered. I’d also like to thank the other professors at the Rothenbuhler Lab, Celeste Welty and Susan Jones, who have helped me find a place at OSU and answered various questions whenever I had them. I’d like to thank the USDA Forest Service Northern Research Station, and particularly researchers Jim Slavicek and Charlie Flower, who allowed me to use their elm research forests, took the time to show me around their facility, and discussed with me their research to help me choose trees appropriate for my studies. This research was made possible through the funding by the Ohio State University, the Department of Entomology, the OARDC, and the Center for Life Science Education. v Vita Miami University, Oxford, Ohio 2008-2011 ..........................................................................................Research Assistant 2011....................................................................................................B.S. Zoology 2011....................................................................................................B.A. Classical Humanities The Ohio State University, Columbus, Ohio 2013-2015 ..........................................................................................Research Assistant 2015-present .......................................................................................Graduate Teaching Assistant vi Publications Abram, P. K., K. A. Hoelmer, A. Acebes-Doria, H. Andrews, E. H. Beers, J. C. Bergh, R. Bessin, D. Biddinger, P. Botch, M. L. Buffington, M. L. Cornelius, E. Costi, E. S. Delfosse, C. Dieckhoff, R. Dobson, Z. Donais, M. Grieshop, G. Hamilton, T. Haye, C. Hedstrom, M. V. Herlihy, M. S. Hoddle, C. R. R. Hooks, P. Jentsch, N. K. Joshi, T. P. Kuhar, J. Lara, J. C. Lee, A. Legrand, T. C. Leskey, D. Lowenstein, L. Maistrello, C. R. Mathews, J. M. Milnes, W. R. Morrison, A. L. Nielsen, E. C. Ogburn, C. H. Pickett, K. Poley, J. Pote, J. Radl, P. M. Shrewsbury, E. Talamas, L. Tavella, J. F. Walgenbach, R. Waterworth, D. C. Weber, C. Welty, and N. G. Wiman. 2017. Indigenous arthropod natural enemies of the invasive brown marmorated stink bug in North America and Europe. J Pest Sci. 90: 1009–1020. Stasek, D. J., J. N. Radl, and T. O. Crist. 2018. The functional response and prey preference of generalist Nabis (Hemiptera: Nabidae) predators to leafhopper prey (Hemiptera: Cicadellidae). Can Entomol. 150: 190–200. Stasek, D. J., J. N. Radl, and T. O. Crist. 2017. The effects of dispersal and predator density on prey survival in an insect-red clover metacommunity. J Insect Sci. 18. Field of Study Major Field: Entomology vii Table of Contents Abstract ......................................................................................................................................... ii Dedication .................................................................................................................................... iv Acknowledgments......................................................................................................................... v Vita ............................................................................................................................................... vi List of Figures .............................................................................................................................. xi List of Tables .............................................................................................................................. xii List of Graphs ............................................................................................................................ xiii Chapter 1: History, Biology, and Importance of Orchestes steppensis ........................................ 1 1.1 History and Discovery of Orchestes steppensis .................................................... 1 1.2 Biology of O. steppensis ....................................................................................... 4 1.3 Importance of O. steppensis as a Pest of Elms ................................................... 13 Chapter 2: Field Evaluations of Adult Orchestes steppensis feeding preference ....................... 19 2.1 Introduction ......................................................................................................... 19 2.2 Objective and Hypotheses ................................................................................... 22 2.3 Materials and Methods ........................................................................................ 23 2.4 Results ................................................................................................................