Routes of Pesticide Exposure in Solitary, Cavity-Nesting Bees

Declines of pollinator health and their populations continue to be commercial and ecological concerns. Agricultural practices, such as the use of agrochemicals, are among factors attributed to honey bee (Apis mellifera L. (Hymenoptera: Apidae)) population losses and are also known to have negative effects on populations of managed non-Apis pollinators. Although pesticide registration routinely requires evaluation of impacts on honey bees, studies of this social species may not reveal important pesticide exposure routes where managed, solitary bees are commonly used. Studies of solitary bees offer additional bee models that are practical from the aspect of availability, known rearing protocols, and the ability to assess effects at the individual level without confounding factors associated with colony living. In addition to understanding bees, it is further important to understand how pesticide characteristics determine their environmental whereabouts and persistence. Considering our research expertise in advancing the management of solitary bees for crop pollination, this forum focuses on routes of pesticide exposure experienced by cavity-nesting bees, incorporating the relative importance of environmental contamination due to pesticide chemical behaviors. Exposure routes described are larval ingestion, adult ingestion, contact, and transovarial transmission. Published research reports of effects of several pesticides on solitary bees are reviewed to exemplify each exposure route. We highlight how certain pesticide risks are particularly important under circumstances related to the cavity nesters.