Joint toxic effects of thiamethoxam and flusilazole on the adult worker honey bees (Apis mellifera L.)

Authors: WANG, DOU - Zhejiang Academy Of Agricultural Sciences; LV, LU - Zhejiang Academy Of Agricultural Sciences; GAO, ZHONGWEN - Nankai University; Zhu, Yu Cheng; WENG, HONGBIAO - Zhejiang Academy Of Agricultural Sciences; YANG, GUILING - Zhejiang Academy Of Agricultural Sciences; WANG, YANHUA - Zhejiang Academy Of Agricultural Sciences

Submitted to: Journal of Hazardous Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2022
Publication Date: 12/2/2022
Citation: Wang, D., Lv, L., Gao, Z., Zhu, Y., Weng, H., Yang, G., Wang, Y. 2022. Joint toxic effects of thiamethoxam and flusilazole on the adult worker honey bees (Apis mellifera L.). Journal of Hazardous Materials. https://doi.org/10.1016/j.envpol.2022.120806.
DOI: https://doi.org/10.1016/j.envpol.2022.120806

Interpretive Summary: Pollinator insects are routinely exposed to a complex mixture of many different pesticides. However, traditional environmental risk assessment based on ecotoxicological data for single substances does not guarantee an adequate level of protection. The aim of this study was to assess the potential effects that occur when honey bee workers are simultaneously exposed to thiamethoxam (TMX) and flusilazole (FSZ). Results displayed that TMX possessed a higher toxicity to honey bee (LC50 value is 0.11 mg a.i. L-1) than FSZ (LC50 value is738 mg a.i. L-1). The mixture of TMX and FSZ exhibited acute synergistic effect on the pollinators. Meanwhile, the activities of four enzymes (SOD, Capase3, Capase9, and PPO), as well as the expressions of six genes (abaecin, dorsal-2, defensin-2, vtg, capase-1, and CYP6AS14) related to oxidative stress, immune response, lifespan, cell apoptosis and detoxification metabolism were significantly altered in the individual and mixture exposures compared with those in the control group. Our findings indicated that the synergistic mixtures may pose a potential risk to honey bees whenever the pesticides appeared concurrently in agriculture, and also indicated that there is an urgent need to study the mixture toxicity of pesticides because the toxicity assessment from individual pesticide towards honey bees may underestimate the toxicity in realistic conditions. Overall, the present results clearly helped to understand the potential contribution of pesticide mixtures to the decline of bee populations.

Technical Abstract: Insect pollinators are routinely exposed to a complex mixture of many pesticides. However, traditional environmental risk assessment is only carried out based on ecotoxicological data of single substances. In this context, we aimed to explore the potential effects when worker honey bees (Apis mellifera L.) were simultaneously challenged by thiamethoxam (TMX) and flusilazole (FSZ). Results displayed that TMX possessed higher toxicity to A. mellifera (96-h LC50 value of 0.11 mg a. i. L-1) than FSZ (96-h LC50 value of 738 mg a. i. L-1). Furthermore, the mixture of TMX and FSZ exhibited an acute synergistic impact on the pollinators. Meanwhile, the activities of SOD, caspase 3, caspase 9, and PPO, as well as the expressions of six genes (abaecin, dorsal-2, defensin-2, vtg, caspase-1, and CYP6AS14) associated with oxidative stress, immune response, lifespan, cell apoptosis, and detoxification metabolism were noteworthily varied in the individual and mixture challenges than at the baseline level. These data revealed that it is imminently essential to investigate the combined toxicity of pesticides since the toxicity evaluation from individual compounds toward honey bees may underestimate the toxicity in realistic conditions. Overall, the present results could help understand the potential contribution of pesticide mixtures to the decline of bee populations.