Andrena spp. Fabricius (Hymenoptera: Andrenidae) Nesting Density in Lowbush Blueberry Vaccinium angustifolium Aiton (Ericales: Ericaceae) Influenced by Management Practices

Abstract:  Andrena are one of the most important wild bee pollinators in lowbush blueberry, and crop management decisions may impact their density in the crop field. Prune method (burning versus mowing) and crop cycle may influence Andrena abundance and nesting decisions, and influence pollination services to this pollinator dependent crop. We measured spring soil temperatures and counted mining bee tumuli in lowbush blueberry fields over two years. In the second year, we measured the influence of lowbush blueberry stem density on soil temperature. We recorded Andrena visitation to nearby crop fields to see if tumuli density corresponded with Andrena visitation rates. Burned fields supported higher densities of tumuli, especially in 2015. Fields managed on a split cycle supported higher densities of tumuli than non-split fields. Soil surface temperatures were higher in burned fields in 2015, but not in 2016. Stem density exerted a greater effect on temperature than pruning method in 2016, and may moderate subsoil temperature. Tumuli densities were not a predictor of Andrena flower visitor abundance. Based upon known richness and relative abundance of the Andrena assemblage associated with the crop, we deduced the most likely species of tumuli occupants. The implications of these findings are discussed.