University of Wisconsin - Madison Madison, Wisconsin
Global honey bee shortages require a greater reliance on the pollination services of wild bees for crop production. While wild bees likely play a vital role in crop pollination, their specific contribution to many pollinator-dependent crops is not known. Furthermore, wild bees are highly responsive to landscape context, suggesting that their contribution may vary in response to the landscape. Therefore, we assessed the contribution of wild bees and honey bees to cranberry yield in central Wisconsin (USA) across a landscape gradient and at marshes with and without honey bees in order to explore how yield changed due to differences in the bee community (honey bee: wild bee ratio). We found that the contribution of bees to cranberry yield varies from year to year but is consistent regardless of the ratio of honey bees to wild bees and the landscape context of the marsh. Open plots obtained yields ~1.3 -- 1.9x greater than caged plots where bees were excluded. These results suggest that wild bees contribute significantly to cranberry yields regardless of the presence of managed honey bees. In addition, we found a positive relationship between overall cranberry yields and cranberry flowering upright density regardless of landscape or bees, suggesting that bees contribute consistently to cranberry yield across a range of local agronomic management practices that also contribute to overall crop yield. In summary, irrespective of the relative composition of the bee community, including when honey bees are absent, bees increase cranberry yield by ~30-90%.
