Biomarker responses and lethal dietary doses of tau-fluvalinate and coumaphos in honey bees: Implications for chronic acaricide toxicity

Evidence suggests that acaricide residues, such as tau-fluvalinate and coumaphos, are very prevalent in honey bee colonies worldwide. However, the endpoints and effects of chronic oral exposure to these compounds remain poorly understood. In this study, we calculated LC50 and LDD50 endpoints for coumaphos and tau-fluvalinate, and then evaluated in vivo and in vitro effects on honey bees using different biomarkers. The LDD50 values for coumaphos were 0.539, and for tau-fluvalinate, they were 12.742 in the spring trial and 8.844 in the autumn trial. Chronic exposure to tau-fluvalinate and coumaphos resulted in significant changes in key biomarkers, indicating potential neurotoxicity, xenobiotic biotransformation, and oxidative stress. The Integrated Biomarker Response was stronger for coumaphos than for tau-fluvalinate, supporting their relative lethality. This study highlights the chronic toxicity of these acaricides and presents the first LDD50 values for tau-fluvalinate and coumaphos in honey bees, providing insights into the risks faced by colonies.