The complementary role of crops, weeds, and pollinator plantings in the diet of honey bees managed in agricultural environments

The agricultural landscape has the potential to support honey bees with floral resources including crops, weeds, and pollinator habitat enhancement plantings. During bloom, mass-flowering crops such as soybeans can be exploited by foraging bees to collect large quantities of pollen and nectar. Weeds growing along field margins or roadsides, which are often present through the foraging season, can play a supplementary role in the pollinator diet. In addition, pollinator habitat enhancement plantings, which typically bloom consistently, may introduce dietary diversity. The synergistic role of these resources in the diet of honey bee colonies located in the agroecosystem is poorly understood. This study aimed to identify the flowers in this landscape that contribute most to honey production. Twelve apiaries along a gradient of agricultural intensity were monitored in 2019 and 2020. Continuous colony weight data was collected to identify periods of nectar flow and dearth. Pollen metabarcoding was used to identify floral sources of nectar collected from study colonies. Glycine (soybean) was detected alongside Trifolium (clover) in summer nectar samples, accompanied by weight gain at many apiaries located in agriculturally intensive sites. Plants commonly present in supplemental plantings, including Solidago (goldenrods) and Trifolium (clovers), were detected in autumn honey samples. These results suggest that soybean flowers are contributing to summer colony weight gain and honey production. In addition, the complementary potential of the agricultural landscape in supporting honey bee foraging is demonstrated. This study expands our understanding of honey bee foraging in landscapes dominated by corn and soybean agriculture.