Assessing local and landscape drivers of pesticide risk to a native ground-nesting bee (Xenoglossa pruinosa)

Pesticide exposure is a major contributor to pollinator declines. Current risk assessments focus on honeybees (Apis mellifera) and assume nectar is the primary route of exposure. However, this neglects key aspects of the natural history of native bees, including soil contact for ground-nesting species. We first characterized pesticide residues in a Cucurbita (squash) growing landscape and then assessed how potential pesticide exposure and landscape composition could affect the native bee community, including Xenoglossa (Peponapis) pruinosa, a specialist ground-nesting pollinator of Cucurbita crops. Specifically, we recorded pollinator abundance at 17 conventionally managed pumpkin fields in Texas and quantified pesticide residues in nectar, pollen, soil, and individual bees. We expected bee abundance to be lower in sites with greater pesticide exposure and higher in sites with greater natural habitat cover. In addition to comparing pesticide risk to pollinator abundance, we assessed whether detected residues corresponded with Cucurbita spray records. We found that the pesticides detected were not generally explained by Cucurbita spray records and that overall pesticide richness was lower in landscapes with greater habitat richness. As we continue our analyses we aim to evaluate whether incorporating species-specific exposure routes improve understanding of pesticide threats to native pollinators and help refine future risk assessment frameworks.