Wildflower plantings in commercial agroecosystems: The effects on pollinators, predators, herbivores, and floral communities A DISSERTATION SUBMITTED TO THE FACULTY OF UNIVERSITY OF MINNESOTA BY Eric Gordon Middleton IN PARTIAL FULLFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Ian V. MacRae and George E. Heimpel, Advisors August 2020 © Eric Gordon Middleton 2020 Acknowledgements There are many people who helped in large and small ways during my time in graduate school that deserve recognition. While the road to this dissertation has not always been a smooth one, the support of colleagues, friends, and family have made it not only possible, but thoroughly enjoyable. For that, I am very grateful. I would first like to thank my advisors Dr. Ian MacRae and Dr. George Heimpel for their mentorship and guidance, and for trusting me with the ownership of my project. Committee members Dr. Dan Cariveau and Dr. Elizabeth Borer provided valuable advice and feedback throughout my graduate career. Outside of my committee, Dr. Sujaya Rao helped me gain experience as a teacher and a leader, and has always been willing to offer counsel and advice. I would also like to thank Dr. Christopher Philips for bringing me on as a student in the first place and setting me on my course of study. This work would not have been possible without funding and support from numerous sources. I thank NRC-SARE and AREA II Potato Growers Association for providing operational funds, and the University of Minnesota’s Doctoral Dissertation Fellowship, the MGK Fellowship, the Bell Museum’s Dayton Fellowship, and the MnDRIVE Global Food Ventures program for contributing to my stipend. Just as important were all of the students and staff who contributed to my project and to my development as a scientist. Thank you Lindsey Christianson, Grace Sward, and Sydney Glass for assistance in the lab and field. Thank you to all of the members of Frenatae for providing a welcoming community. And thank you to the undergraduate workers Noah Linck, Joe Nelson, Gus Fedje-Johnson, Lily Briggs, Erik Lucas, Lexie i Ogdahl, Caroline Hofmeister, Eli Kleinschmidt, Bailey Brandel, and Samantha Meyers for all of your hard work and dedication. Lastly, I have to thank my parents John and Marge for their constant support, for reading through drafts of papers, and for providing feedback whenever I needed it. I am truly fortunate to have such a supportive family, who exposed me to critically thinking and the wonder of nature from an early age. And finally, thank you to my partner Elissa, who inspires me to be a better scientist and always encourages me to stop and look at the bugs. ii Table of Contents Acknowledgements...............................................................................................................i Table of Contents................................................................................................................iii List of Tables.....................................................................................................................vii List of Figures.....................................................................................................................ix Voucher Specimens..........................................................................................................xiii Chapter 1: Introduction 1.1 Declines in Insect Abundance and Ecosystem Services....................................1 1.2 Methods to Preserve Insects and Services.........................................................3 1.3 Floral Plantings..................................................................................................5 1.4 Scope of Dissertation.........................................................................................7 Chapter 2: Floral community and herbivores: Evaluating a commercially available floral seed mixture when established on-farm 2.1 Overview............................................................................................................8 2.2 Introduction........................................................................................................9 2.3 Materials and Methods 2.3.1 Experimental Design.........................................................................12 2.3.2 Floral Sampling.................................................................................14 2.3.3 Herbivore Sampling..........................................................................16 2.4 Results 2.4.1 Floral Communities..........................................................................17 2.4.2 Herbivores.........................................................................................18 2.5 Discussion iii 2.5.1 Floral Establishment.........................................................................19 2.5.2 Herbivores.........................................................................................23 2.6 Conclusions......................................................................................................25 2.7 Acknowledgements..........................................................................................25 2.8 Figures and Tables...........................................................................................27 Chapter 3: Floral plantings in large-scale commercial agroecosystems support both pollinators and arthropod predators 3.1 Overview..........................................................................................................34 3.2 Introduction......................................................................................................35 3.3 Materials and Methods 3.3.1 Experimental Design.........................................................................38 3.3.2 Floral Sampling.................................................................................39 3.3.3 Pollinator Sampling..........................................................................40 3.3.4 Predator Sampling.............................................................................41 3.3.5: Data Analysis…...............................................................................41 3.4 Results 3.4.1 Pollinators and Predators in Margins................................................43 3.4.2 Predators and Predators in Crops…..................................................44 3.5 Discussion 3.5.1 Pollinators.........................................................................................45 3.5.2 Predators...........................................................................................48 3.6 Conclusions......................................................................................................50 3.7 Acknowledgements..........................................................................................50 iv 3.8 Figures and Tables...........................................................................................52 Chapter 4: Wildflower plantings in commercial agroecosystems promote generalist predators of Colorado potato beetle 4.1 Overview..........................................................................................................64 4.2 Introduction......................................................................................................64 4.3 Materials and Methods 4.3.1 Experimental Design.........................................................................68 4.3.2 Insect Sampling.................................................................................69 4.3.3 Measuring Predation.........................................................................71 4.3.4 Overwintering Colorado potato beetle..............................................72 4.4 Results 4.4.1 Colorado potato beetle predators......................................................73 4.4.2 Sentinel Prey Removal......................................................................74 4.4.3 Colorado potato beetle abundance....................................................74 4.4.4 Sentinel potato plants........................................................................75 4.5 Discussion 4.5.1 Do floral plantings affect the abundance of known predators of CPB? .........................................................................................................75 4.5.2 Do floral plantings increase predation of CPB eggs masses?...........78 4.5.3 How do floral plantings influence the abundance of CPB within adjacent potato fields? ...............................................................................79 4.5.4 Do floral plantings provide improved overwintering habitat or refuge for CPB? ....................................................................................................80 v 4.6 Conclusions......................................................................................................81 4.7 Acknowledgements..........................................................................................81 4.8 Figures and Tables...........................................................................................83 Literature Cited...............................................................................................................90 Appendix 1......................................................................................................................101 Appendix 2......................................................................................................................103 Appendix 3......................................................................................................................104