Honey bee foraging in a Midwestern agroecosystem

Honey bees (Apis mellifera) depend on large amounts of floral nectar and pollen to meet their dietary needs, an average colony requiring an estimated 120 kg of nectar and 20 kg of pollen each year. Floral abundance, diversity, and temporal availability are, therefore, of central importance to colony survival and productivity. Of particular concern is the capacity of intensively managed agroecosystems to sustain sufficient floral communities to support the foraging needs of local honey bee colonies. We explored this question by studying the pollen collected by colonies in a high intensity corn/soybean agroecosystem in central Ohio, USA. Pollen was collected from a total of twelve colonies at three sites from mid-April to mid-June. Collected pollen was visually sorted by color and weighed to estimate the number and relative importance of different floral species. Then, each color class was microscopically analyzed and identified to the lowest possible taxonomic level using standard melissopalynological techniques. Our findings indicate that bees in Midwestern agroecosystems collect pollen from a surprisingly diverse floral assemblage but that a very small number of species dominate the total amount of pollen collected. The abundance and distribution these species is heavily influenced by the agricultural practices of tilling and herbicide application and by the area of forest patches within the agricultural matrix.