Pesticide transfer between solitary bee nesting materials and provisions – Implications for larval exposure

Authors: LUU, CALVIN - Utah State University; HAGEMAN, KIMBERLY - Utah State University; SINGER, THERESA - Retired ARS Employee; Cox-Foster, Diana; Graham, Kelsey

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2025
Publication Date: 8/25/2025
Citation: Luu, C., Hageman, K.J., Singer, T.L., Cox-Foster, D.L., Graham, K.K. 2025. Pesticide transfer between solitary bee nesting materials and provisions – Implications for larval exposure. Environmental Science and Technology. 59:35. https://doi.org/10.1021/acs.est.5c08032.
DOI: https://doi.org/10.1021/acs.est.5c08032

Interpretive Summary: Pesticide exposure can affect bee health. For solitary bees that nest in cavities there is potential added exposure from pesticides in plant materials or soil used in the nests. Understanding how pesticide chemical properties interact with the nest materials and move into the pollen provisions will enable this added exposure to be included in pesticide risk assessments. This publication reports experimental data that quantifies the amount of insecticides or fungicides that can move from nesting material into the pollen provisions.

Technical Abstract: Solitary cavity-nesting bees have distinguishable life histories resulting in pesticide risk exposures, especially to larvae, that differ from exposure routes for social bees. Pesticides in nesting materials, such as leaves and soil, may transfer pesticides into food provisions, which would result in added oral exposure to pesticides for solitary bee larvae whose mothers use resources from areas where agrochemicals are used. Thus, the objective of this work was to determine if pesticides in nesting materials will transfer into alfalfa leafcutting bee (ALCB) provisions or blue orchard bee (BOB) provisions. We developed laboratory experiments to model pesticide transfer from alfalfa leaves to ALCB provisions and from soil to BOB provisions. Two insecticides of interest for ALCBs, chlorpyrifos and lambda-cyhalothrin, transferred from alfalfa leaves into provisions, and two of the three pesticides of interest for BOBs, bifenthrin and fluxapyroxad, transferred from soil into BOB provisions. Lambda-cyhalothrin did not transfer from soil into BOB provisions in these experiments. We determined that the nesting material contribution to overall pesticide risk for ALCB larvae was in the range of concern, while that for BOB larvae was low, as the transferred concentrations from soil into provisions were minimal.