Responses of honey bees to lethal and sublethal doses of formulated clothianidin alone and mixtures

Authors: YAO, JIANXIU - Kansas State University; Zhu, Yu Cheng; Adamczyk, John

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2018
Publication Date: 6/8/2018
Citation: Yao, J., Zhu, Y., Adamczyk Jr, J.J. 2018. Responses of honey bees to lethal and sublethal doses of formulated clothianidin alone and mixtures. Journal of Economic Entomology. 1-9. https://doi.org/10.1093/jee/toy140.
DOI: https://doi.org/10.1093/jee/toy140

Interpretive Summary: The widespread use of neonicotinoid insecticides has inevitably sparked concern over the toxicity risk to honey bees. In this study, feeding treatments with the clothianidin formulation Belay® at 2.6 ppb (residue concentration) or its binary mixtures with 5 representative pesticides (classes) did not show significant influence on adult survivorship, but all treatments caused lower body weight than control. Most binary mixtures at residue levels showed minor additive effect or no interaction on body weight loss, and synergistic interaction was detected only from the mixture of clothinidin+'-cyhalothrin. Chlorpyrifos alone and the mixture of chlorpyrifos+clothianidin significantly suppressed esterase activity, while most treatments of individual pesticides and mixtures had no effect on esterase and glutathione S-transferase (GST) activities. However, clothianidin at 2.6 ppb significantly enhanced P450 oxidase activity by 19%. The dose response assay data showed that the 48-h oral toxicity (median lethal concentration: LC50) of Belay® was 0.53 ppm of the active ingredient clothianidin. In addition to incurring 50% mortality, clothianidin at 0.53 ppm significantly reduced bee body weight of survivors by 12%. P450 activities were also significantly induced at 24 and 48 h in Belay-treated bees, while no significant difference was found in GST and esterase activities. Further examinations revealed that the expression of an important CYP9q1 P450 detoxification gene was significantly induced by clothianidin. Thus, data consistently indicated that P450s were involved in clothianidin detoxification in honey bees. Despite minor sublethal impacts on survivors and 6-fold lower susceptibility in a Stoneville (Mississippi, USA) bee population, clothianidin had very high oral and spray contact toxicity.

Technical Abstract: The widespread use of neonicotinoid insecticides has inevitably sparked concern over the toxicity risk to honey bees. In this study, feeding treatments with the clothianidin formulation Belay® at 2.6 ppb (residue concentration) or its binary mixtures with 5 representative pesticides (classes) did not show significant influence on adult survivorship, but all treatments caused lower body weight than control. Most binary mixtures at residue levels showed minor additive effect or no interaction on body weight loss, and synergistic interaction was detected only from the mixture of clothinidin+'-cyhalothrin. Chlorpyrifos alone and the mixture of chlorpyrifos+clothianidin significantly suppressed esterase activity, while most treatments of individual pesticides and mixtures had no effect on esterase and glutathione S-transferase (GST) activities. However, clothianidin at 2.6 ppb significantly enhanced P450 oxidase activity by 19%. The dose response assay data showed that the 48-h oral toxicity (LC50) of Belay® was 0.53 ppm of the active ingredient clothianidin. In addition to incurring 50% mortality, clothianidin at 0.53 ppm significantly reduced bee body weight of survivors by 12%. P450 activities were also significantly induced at 24 and 48 h in Belay-treated bees, while no significant difference was found in GST and esterase activities. Further examinations revealed that the expression of an important CYP9q1 detoxification gene was significantly induced by clothianidin. Thus, data consistently indicated that P450s were involved in clothianidin detoxification in honey bees. Despite minor sublethal impacts on survivors and 6-fold lower susceptibility in a Stoneville (Mississippi, USA) bee population, clothianidin had very high oral and spray contact toxicity.