Management of Overwintering Cover Crops Influences Floral Resources and Visitation by Native Bees.

The incorporation of cover crops into annual crop rotations is one practice that is used in the Mid-Atlantic United States to manage soil fertility, suppress weeds, and control erosion. Additionally, flowering cover crops have the potential to support beneficial insect communities, such as native bees. Because of the current declines in managed honey bee colonies, the conservation of native bee communities is critical to maintaining "free" pollination services. However, native bees are negatively affected by agricultural intensification and are also in decline across North America. We conducted two experiments to assess the potential of flowering cover crops to act as a conservation resource for native bees. We evaluated the effects of cover crop diversity and fall planting date on floral resource availability and visitation by native bees for overwintering flowering cover crop species commonly used in the Mid-Atlantic region. Cover crop species, crop rotation schedule, and plant diversity significantly influenced floral resource availability. Different cover crop species not only had different blooming phenologies and winter survival responses to planting date, but attracted unique bee communities. Flower density was the primary factor influencing frequency of bee visitation across cover crop diversity and fall planting date treatments. The results from these experiments will be useful for informing recommendations on the applied use of flowering cover crops for pollinator conservation purposes.