Better blueberry production: How pollinator facilitation between honey bees and bumble bees fits in

Managed bees and the pollination services they provide are crucial for the success of the southern highbush blueberry production system. Blueberry is highly dependent upon insect pollination with fruit set and berry weight both decreasing dramatically in their absence. In Florida, this reliance is complicated by early flowering phenology that often renders the services of wild native bees too late to produce marketable fruit and growers frustrated with unsatisfactory pollination. Resultantly, a heavy reliance on honey bees (Apis mellifera L.) and managed bumble bees (Bombus impatiens) has been observed, but this strategy can prove costly and can leave growers with pollination problems. Previous research in this system found that increasing bumble bee stocking density improves fruit set and yield despite low overall visitation rates as compared to honey bees, indicating a disproportionately positive impact on blueberry pollination likely in part to their ability to buzz pollinate. However, the use of these two managed pollinators together to achieve optimal pollination has not been well studied despite the growing proportion of farmers who invest in both pollinators during bloom. To fill this gap, we set out to test the hypothesis that managed bumble bee deployment facilitates and improves the efficacy of non-buzz pollinating honey bees by increasing pollen release and direct interactions that initiate movement across fields. Utilizing large field cages, we found that managed bumble bee deployment in conjunction with honey bees improves pollination outcomes when compared to deployment of only honey bees with pollinator facilitation as a potential mechanism.