Defining Bee Pollinator Community Composition in Tennessee Soybean

Two planting dates of various soybean varieties were planted in Jackson and Knoxville, TN during 2018 and 2019 with the overall intent of surveying the diversity bee (Hymenoptera) genera in these agroecosystems and also to assess the potential for using late maturing soybean as a food resource for bees during the dearth of floral resources that often occurs during the fall. We also investigated how manipulating planting dates and soybean variety selection affected the occurrence of insect pests that occurred in the soybean.

Both active (netting) and passive (bee bowls and blue-vane traps) sampling were used to collect the bees, and during the course of this study, 2,294 bees comprising 4 families and 20 genera were caught. However, the indices of generic richness and diversity were generally higher Jackson. Both locations had a dominant genus that was collected much more frequently than others, specifically Melissodes (Apidae) in Jackson and Lasioglossum (Halictidae) in Knoxville, but the specimens collected in Jackson were more evenly distributed across genera than in Knoxville. Foraging on the floral resources in our soybean plots clearly increased around mid-August and was sustained into mid-September. However, it would likely take substantial acres to meaningfully impact overall pollinator populations over a wide geography, and one limitation was that the varieties which seemed to fit best is this role had a determinate growth pattern. Thus, they would only provide a significant food source for pollinators during a relatively short blooming window during the R1 and R2 growth stages.

The occurrence of insect pests in soybean often followed a predictable pattern related to the developmental stage of the soybean. Although some pests occurred at economically damaging levels, we did not observe serious insect infestations specifically associated with the use of late soybean maturity groups or the unusually late planting dates in this study. However, these results are not necessarily typical of early vs. late production soybean systems. Yield data were not collected in this study, but yield penalties were evident owing to late planting and the use of later maturing varieties.