The impact of chronic exposure to field-level thiamethoxam on sunflower visitation and yield for Apis cerana

Thiamethoxam (TMX) is one of the most widely used neonicotinoid insecticides. However, it is unclear how TMX alters the flower-visiting behavior and seed production of Apis cerana in sunflowers. We conducted cage experiments to study the impact of chronic exposure (10 days) to TMX at sublethal concentrations of 2.4 μg/kg and 10 μg/kg on the number of flower visits per minute, seed setting percentage, 100-seed weight, and seed yield in sunflowers. Bees treated with TMX demonstrated a significantly lower number of flower visits per minute compared with the control group. Although we did not observe a significant difference in yield parameters between TMX treatments and the control group, a positive correlation was observed between yield and the bees’ flower visitation rate. Our study highlights the concern that exposure to field-level concentrations of TMX could pose a threat to the pollination services provided by A. cerana for other crops and wildflowers.