Synergistic toxicity and physiological impact of thiamethoxam alone or in binary mixtures with three commonly used insecticides on honeybee

Abstract

As one of the most widely used insecticides, thiamethoxam (Th) plays an important role in agriculture pest control but is hazardous to the health of honeybees (Apis mellifera ligustica). In agricultural practice, several types of insecticides are often applied simultaneously, but their synergistic effects on honeybees remain elusive. Here, we treated honeybees with various binary mixtures of insecticides in which a sublethal dose of Th was mixed with three other common insecticides: λ-cyhalothrin (λ-cy), β-cypermethrin (β-cy), and abamectin (Ab). The mortality rates of the groups treated with the insecticide mixtures were higher than that obtained with the pesticides alone. Specifically, the Th + λ-cy and Th + Ab combinations exerted a synergistic effect (P 0.05) on bees, and the mortality rate of this group was almost identical to those of the groups administered these pesticides alone. Furthermore, the Th + λ-cy and Th + Ab mixtures significantly suppressed the activity and expression of glutathione S-transferases (GSTs), which are key detoxification enzymes in insects. This result suggests that the Th + λ-cy and Th + Ab combinations at a given concentration adversely affect the survival of honeybees. Our study provides novel information for the selection of pesticide combinations based on protecting honeybee populations.