Native solitary bees provide economically significant pollination services to confection sunflowers (Helianthus annuusL.) (Asterales:Asteraceae) grown across the northern Great Plains

Authors: MALLINGER, RACHEL - University Of Florida; BRADSHAW, JEFF - University Of Nebraska; VARENHORST, ADAM - South Dakota State University; Prasifka, Jarrad

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2018
Publication Date: 10/22/2018
Citation: Mallinger, R.E., Bradshaw, J., Varenhorst, A.J., Prasifka, J.R. 2018. Native solitary bees provide economically significant pollination services to confection sunflowers (Helianthus annuusL.) (Asterales:Asteraceae) grown across the northern Great Plains. Journal of Economic Entomology. https://doi.org/10.1093/jee/toy322.
DOI: https://doi.org/10.1093/jee/toy322

Interpretive Summary: Pollination by bees and other insects increases yields of many crops, but these benefits vary because of differences in crop varieties or environmental conditions. In this study, we measured the benefits pollinators provided to confection sunflower yields in three states (North Dakota, South Dakota, and Nebraska) over two years, including 10 commercial hybrids. We also looked at how effective specific types of bees were at pollinating sunflowers. Including all locations, years and different sunflower hybrids, pollinators increased confection sunflower yields by 45%, which is a regional economic value of over $40 million and a national value of over $56 million. Most of the benefits to sunflower yields appeared to come from wild bees that specialize on sunflower and related wild plants. Managed honey bee colonies appeared to have little yield benefit to sunflowers in these locations. Our results show that wild bees provide significant economic benefits to confection sunflowers, and practices that preserve or enhance these bee populations help to maintain or increase yields.

Technical Abstract: The benefits of insect pollination to crop yields depend on genetic and environmental factors including plant self-fertility, pollinator visitation rates, and pollinator efficacy. While many crops benefit from insect pollination, such variation in pollinator benefits across both plant cultivars and growing regions is not well documented. In this study, across three states in the northern Great Plains, U.S.A, from 2016–2017, we evaluated the pollinator-mediated yield increases for ten varieties of confection sunflowers, Helianthus annuus L., a plant that is naturally pollinator-dependent but was bred for self-fertility. We additionally measured pollinator visitation rates and compared per-visit seed set across pollinator taxa in order to determine the most efficacious sunflower pollinators. Across all locations and hybrids, insect pollination increased sunflower yields by 45%, which is a regional economic value of over $40 million and a national value of over $56 million. There was, however, some variation in the extent of pollinator benefits across locations and plant genotypes, and such variation was due to differences in both pollinator visitation rates and plant selfing rates. Female Andrena helianthi Robertson and Melissodes spp. were the most common and effective pollinators, while other bees including managed honey bees, Apis mellifera L., small-bodied sweat bees, bumble bees, and male bees were either infrequent or less effective on a per-visit basis. Our results illustrate that wild bees provide significant economic benefits to confection sunflower production, and that conservation and enhancement efforts targeting A. helianthi and Melissodes spp. in particular could result in increased sunflower yields.