University of New Hampshire University of New Hampshire Scholars' Repository Master's Theses and Capstones Student Scholarship Summer 2019 Integrated Organic Management of Cabbage Aphid on Brussels sprouts Alina Sophia Harris University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/thesis Recommended Citation Harris, Alina Sophia, "Integrated Organic Management of Cabbage Aphid on Brussels sprouts" (2019). Master's Theses and Capstones. 1294. https://scholars.unh.edu/thesis/1294 This Thesis is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Master's Theses and Capstones by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. INTEGRATED ORGANIC MANAGEMENT OF CABBAGE APHID ON BRUSSELS SPROUTS BY ALINA SOPHIA HARRIS Sustainable Agriculture and Food Production Systems, University of New Hampshire, 2012 THESIS Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Master of Science in Agricultural Science September 2019 This thesis was examined and approved in partial fulfillment of the requirements for the degree of Master of Science in Agricultural Science by: Thesis Director, Dr. Rebecca Grube Sideman, Extension Professor of Sustainable Agriculture Iago Hale, Associate Professor, Agriculture, Nutrition, and Food Systems Anna Wallingford, Extension Integrated Pest Management Specialist On July 18, 2019 Approval signatures are on file with the University of New Hampshire Graduate School. ii ALL RIGHTS RESERVED ©2019 Alina Sophia Harris iii General Material Disclaimer Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the author or the University of New Hampshire and does not imply its approval to the exclusion of other products or vendors that also may be suitable. iv Acknowledgements I give my deepest gratitude to Becky Grube Sideman who has mentored me with grace over the past decade and served as my advisor in undergraduate and graduate school at UNH. Witnessing her professional life over the years continues to inspire me. She has an authentic attitude, is extremely sharp, well rounded, humble, and connected to the agricultural community. She is a balanced intersection of academic and practical; I value how her applied research contributes directly to the local and global community. As an advisor, she holds me to a high standard and makes herself available for support. She is not overbearing or micromanaging, which has allowed me to find my own workflow. Her encouragement to present my data in both an academic way and to different audiences of local growers and gardeners has been invaluable to me. I cannot thank her enough for her patience with editing this thesis. Thank you to Kaitlyn Orde and Meredith Cogswell for their support while working in the Sideman lab. Many thanks to Talia Levy who began the primary research for this topic in 2017. Thank you to Leah Ford, Madie Hassett, Harrison Pradis-Collins, Kyle Quigley, and Evan Ford for technical expertise in the field and thank you especially to Evan Ford (Farm Manager) and Kyle Quigley (Assistant Farm manager) for hosting me at Woodman Horticultural research farm. Thank you to Iago Hale for being my co-advisor, my committee member, and for reading my thesis. Thank you for making meaningful suggestions in experimental design and connecting me with the Legume Cover Crop Breeding Program to evaluate crimson clover winter hardiness in 2017-18. Thank you to the Hale lab and family for being so welcoming. Thank you to Will Hastings, who gave me advice on the master’s application process at UNH, has been a friend v around the research farm, and a big help on Brussels sprouts harvest day when we donated about 700 stalks to four local food pantries. A big thank you to Anna Wallingford who immediately dug into mentoring me and serving on my committee when she was hired as the Integrated Pest Management specialist upon Alan Eaton’s retirement. Her tenacity for new projects is amazing! Many thanks for her help with identifying hoverflies, advice on rearing hoverfly larvae, and showing me the ropes of analyzing count data with poisson distribution. Thank you to Istvan Miko, the Collection Manager at UNH who has hosted me in the collection room and trained me to pin and label hoverfly specimens that I will contribute to the UNH collection. Thank you to Don Chandler who has been a friendly, supportive face in the collection room and sharing his hoverfly wisdom. Thank you to Alan Eaton, who laid the foundation of my insect knowledge for this project and helped me identify insects in the field. We both were thrilled to find entomopathogenic fungi on aphids in the field and send samples out for identification. Thank you to Margaret Skinner and Agrin Davari for entomopathogenic fungi identification in 2017 and 2018. Thank you to the Brassica Pest Collaborative, particularly Sue Scheufele and Genevieve Higgins, who shared their hoverfly identification knowledge and compared specimens at UNH collection room. Thank you to Genevieve for her microscope photographs of hoverflies and connecting me with Michelle Locke at the Canadian National Collection of Insects. Thank you to Michelle for official hoverfly identification. Thank you to Sue Scheufele for hosting Brassica Pest collaborative webinars, distributing fact sheets and research reports, taking polls that contributed to this thesis, and managing one of the funding sources for this project, the Northeast-SARE grant, subaward LNE18-365. vi Thank you to Daniela Dutra Elliott, my friend and former supervisor at the University of Hawaii for sharing the love of similar growing practices and giving me hands-on experience with implementation of insectary plants in the lab gardens that we managed. Together, we experimented with white clover (Trifolium repens) and perennial peanut (Arachis glabrata) as living mulches, pigeon pea (Cajanus cajan) and sunn hemp (Crotalaria juncea) as living borders, basil and cilantro accession trials (that attracted many beneficial insects), buckwheat and Lablab purpueus as cover crops, and plantings of zinnias and cosmos for beautiful butterfly attractants. Thank you for inspiring, encouraging and supporting me to go to graduate school. Finally, thank you for the cabbage and broccoli trials that highlighted how truly awful aphids can be on organically managed Brassicas; an inspiration that lead to tackling the questions in this thesis. Thank you to our funding sources: The NH Vegetable and Berry Growers’ Association The NH Agricultural Experiment Station The USDA NIFA Hatch Project NH00635 Northeast-SARE grant, subaward LNE18-365 vii List of Tables Table 1. Insecticide treatments used against cabbage aphid: tradenames, manufacturer, location, active ingredient, and rate of insecticide concentrate used per three gallons of water ................. 54 Table 2. Application dates of insecticides to experimental plots in 2016 and 2017. .................... 63 Table 3. Insectary plant days to maturity, seeding, and transplanting dates, grown in Durham, NH in 2017. Days to maturity data were provided by seed suppliers.......................................... 83 Table 4. Insectary plant days to maturity, seeding, and transplanting dates, grown in Durham, NH in 2018 .................................................................................................................................... 84 Table 5. Mean number of alyssum flowers and hoverflies per 314 in2 per four minutes observed on alyssum throughout the 2017 season. .................................................................................... 100 Table 6. Mean hoverfly density per 314 in2 per four-minute interval in Durham, NH in 2017…103 Table 7. Mean of abiotic factors from 10:00 AM to 12:00 PM during sample days in Durham, NH in 2017 .................................................................................................................................. 104 Table 8. Mean hoverfly density per 314 in2 per four-minute time interval in Durham, NH in 2018............................................................................................................................................. 109 Table 9. Mean of abiotic factors from 10:00 AM to 12:00 PM during sample days in Durham, NH in 2018. ................................................................................................................................. 110 Table 10. Number of hoverfly species collected per eight sweepnet samples per insectary plant treatment over time, 2018. .......................................................................................................... 121 Table 11. Mean number (± SEM) of insects per six Brussels sprout leaves at increasing distances from insectary plants on 10 Oct 2017 ......................................................................................... 162 viii Table 12. Mean number (± SEM) of insects per yellow sticky card at increasing distances from insectary plants............................................................................................................................ 164 List of Figures Figure 1. The lifecycle of cabbage aphid in a cold climate with all four life stages .................... 24 Figure 2. (A) View of Brussels sprouts underneath