Honey bee hives decrease the conservation value and pollination services of on-farm pollinator refuges

Authors: Angelella, Gina; MCCULLOUGH, CHRISTOPHER - Virginia Tech; O'ROURKE, MEGAN - National Institute Of Food And Agriculture (NIFA)

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2021
Publication Date: 2/5/2021
Citation: Angelella, G.M., Mccullough, C.T., O'Rourke, M.E. 2021. Honey bee hives decrease the conservation value and pollination services of on-farm pollinator refuges. Journal of Applied Ecology. 3202 (2021). https://doi.org/10.1038/s41598-021-81967-1.
DOI: https://doi.org/10.1038/s41598-021-81967-1

Interpretive Summary: Pollinator refuges, or wildflower meadows designed to provide native blooms throughout the growing season, are often planted on farms to help conserve wild pollinators and promote crop pollination services. However, it is not clear whether the goals of pollinator refuges to conserve wild bees and enhanced crop pollination are compatible with managed honey bee hives, because competition with honey bees can decrease wild bee abundance and even decrease plant seed set. Researchers at Virginia Tech, one of whom is currently a scientist at USDA-ARS Wapato, WA, surveyed wild bee populations and measured strawberry and winter squash fruit set on farms in the Mid-Atlantic with and without pollinator refuges and honey bee hives in 2017 and 2018. They found that wild bee abundance and species richness decreased on farms with hives, and that fruit set decreased on farms with hives as well. Pollinator refuges enhanced fruit set in only one year and did not offset the decreases in wild bees or fruit set associated with hives. Overall, this work shows that honey bee hives could reduce the pollination services and conservation value of pollinator refuges on farms

Technical Abstract: 1. Pollinator refuges planted on farms are designed to boost floral resources in order to mitigate wild pollinator declines and promote crop pollination services. It is unclear, however, whether the goals of pollinator refuges to conserve wild bees and boost pollinator-dependent crop production are compatible with managed honey bee (Apis mellifera L.) hives. Competition between managed and wild bees for floral resources can suppress wild bee abundance and plant seed set. 2. Here, we examined whether on-farm pollinator refuges and honey bee hives interact to influence wild bee communities and two pollinator-dependent crops. We quantified wild bee abundance, diversity, richness, and evenness as well as strawberry and winter squash fruit set across 21 farms in the Mid-Atlantic U.S. with and without pollinator refuges and honeybee hives. 3. Wild bee abundance and species richness decreased, and evenness increased on farms with hives, and the effects on abundance and richness were more consistent on farms with pollinator refuges than without. In turn, species evenness was negatively associated with fruit set and species richness was positively associated with fruit set in winter squash. 4. Fruit set was lower overall on farms with honey bee hives. Pollinator refuges enhanced fruit set in both crops one of two years of study but did not offset the decreased fruit set associated with hives. 5. Synthesis and applications. This work demonstrates honey bee hives can decrease fruit set and wild bee abundance and species richness on farms. These effects were not attenuated on farms with pollinator refuges. Therefore, honey bee hives may reduce the pollination services and conservation value conferred by on-farm pollinator refuges