5: Understanding differences in chronic oral toxicity of pesticides to honey bee workers of different age groups (1, 10 and 24 day old)

Pesticide risk assessment process for bees is complex and has limitations. OECD guidelines suggest using young bees (maximum 2 days old) for chronic oral toxicity tests. Testing only young bees for risk assessment may not be ideal and may not provide a realistic risk assessment, as honey bee colony is complex and consists of thousands of bees of different age groups and performing different tasks (temporal polyethism). In this study, we examined chronic oral toxicity of an insecticide (Thiamethoxam) to three different age cohorts (1 day old, 10 days old and 24 days old) of worker honey bees. Thiamethoxam (200 ppb) mixed in 40% sucrose solution was fed ad libitum to experimental bees in cages for 10 days. We measured mortality, reactive oxygen and nitrogen species (ROS/RNS), sugar syrup consumption and water consumption in each experimental cage. Our results indicate significant differences in mortality, ROS/RNS and sugar syrup consumption between experimental groups (different age cohorts).