Effect of erythritol, a prospective human-safe insecticide for Drosophila suzukii, on honeybee (Apis mellifera) visitation and brood survival

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), commonly referred to as spotted-wing drosophila, is a problematic pest from Asia that attacks a wide range of small fruits. Erythritol, a non-nutritive sugar, is safe for human consumption but insecticidal to spotted-wing drosophila and is being developed as a human-safe insecticide for berry and cherry crops. Bees most often visit crops while in bloom, while the erythritol spray would be applied post-bloom, minimizing risk to pollinators while maximizing risk to spotted-wing drosophila. Understanding the effect of erythritol on Apis mellifera is important to commercialize our formulations as honey bees have been observed visiting erythritol-treated bushes in small numbers during field trials. We observed visitation frequency at sprayed bushes at various distances to established honey bee hives and found that honey bee visitation was similar among all treatments which would indicate that they are not considerably lured toward the sugar sprays. In Choi et al. (2019), the effect of erythritol consumption by adult honey bees was explored through a laboratory cage-incubation study. Erythritol-fed bee survivorship was comparable to sucrose-fed control bees. Although results showed no toxicity to adults, toxicity to developing brood was previously unknown and was accessed by dripping our erythritol formulations into honey bee brood cells and imitating an unrealistic level of exposure to developing larvae. We found no detriment from both of our formulations in comparison to our control, distilled water. Overall, our results show that our two erythritol formulations cause minimal non-target damage to honey bees.