Mixture toxic effects of thiacloprid and cyproconazole on honey bees (Apis mellifera L.)

Pesticide exposure remains one of the main factors in the population decline of insect pollinators. It is urgently necessary to assess the effects of mixtures on pollinator risk assessments because they are often exposed to numerous agrochemicals. In the present study, we explored the mixture toxic effects of thiacloprid (THI) and cyproconazole (CYP) on honey bees (Apis mellifera L.). Our findings revealed that THI possessed higher acute toxicity to A. mellifera (96-h LC50 value of 216.3 mg a.i. L-1) than CYP (96-h LC50 value of 601.4 mg a.i. L-1). It's worth noting that the mixture of THI and CYP exerted an acute synergistic effect on honey bees. At the same time, the activities of detoxification enzyme cytochrome P450s (CYP450s) and neuro target enzyme Acetylcholinesterase (AChE), as well as the expressions of seven genes (CRBXase, CYP306A1, CYP6AS14, apidaecin, defensing-2, vtg, and gp-93) associated with detoxification metabolism, im -mune response, development, and endoplasmic reticulum stress, were significantly altered in the combined treatment compared with the corresponding individual exposures of THI or CYP. These data indicated that a mixture of THI and CYP could disturb the physiological homeostasis of honey bees. Our study provides a theoretical basis for in-depth studies on the impacts of pesticide mixtures on the health of honey bees. Our study also provides important guidance for the ra-tional application of pesticide mixtures to protect pollinators in agricultural production effectively.

Automated summary

Pesticide exposure remains a significant factor in the decline of insect pollinators. It is necessary to assess the effects of mixtures on pollinator risk assessments due to their frequent exposure to multiple agrochemicals. This study explored the toxic effects of a mixture of thiacloprid and cyproconazole on honey bees and found that the combination exhibited acute synergistic effects and disrupted the physiological homeostasis of honey bees.