Toxicity responses of different bee species to flupyradifurone and sulfoxaflor insecticides reveal species and sex-based variations.

Mason bees (Osmia spp.) are solitary, tunnel-nesting bees. Several species, including the horn-faced bee (Osmia cornifrons) and the blue orchard bee (Osmia lignaria), are commercially managed, primarily for the pollination of fruit trees and tree nuts. They are efficient pollinators and have high pollen fidelity, and so can greatly benefit orchard yields compared to honey bees (Apis mellifera) alone. Apis mellifera are often used as surrogates for other pollinators during pesticide risk assessment. Non-Apis bee species, however, can be more sensitive to certain pesticides, so it is also important to research the impact of novel pesticides on other bee species. This study investigated the effect of two formulated pesticide products containing recently approved active ingredients, sulfoxaflor and flupyradifurone, on the survival of A. mellifera and three species of mason bees (O. lignaria, O. cornifrons, and Osmia californica). Bees were orally exposed to sulfoxaflor or flupyradifurone and their survival was measured over four days following exposure. Bee sensitivity to the insecticides varied by species and sex of bee. Apis mellifera was the least sensitive, followed by O. cornifrons, with O. lignaria and O. californica as the most sensitive. Male Osmia spp. bees were less sensitive than females. These insecticides may pose a higher risk to the health of Osmia spp. compared to A. mellifera.