The Effects of Exposure to Flupyradifurone on Survival, Development, and Foraging Activity of Honey Bees (Apis mellifera L.) under Field Conditions

SIMPLE SUMMARY: Honey bees play an invaluable role in ecosystem stability and global food security. Recently, much attention has been directed toward the safety of pesticides to bees. Flupyradifurone (FPF) is a new butenolide insecticide and is considered friendly to honey bee fitness according to risk assessment procedures. Although no significant side-effects on bee colony strength parameters at FPF field-realistic concentration, laboratory experiments have demonstrated that FPF has multiple negative effects on the behavior of individual honey bees. The information suggested that FPF is posing potential risks to honey bees. In this study, we found that the survival rate of bees exposed to FPF was statistically significantly reduced, whereas there were no negative effects on larvae development nor foraging activity. In addition, immune- and detoxification-related genes were upregulated in exposed foragers and newly emerged bees, suggesting that more important synergistic and behavioral effects that can affect colony fitness should be explored in the future. ABSTRACT: Flupyradifurone (FPF) is a novel systemic nAChR agonist that interferes with signal transduction in the central nervous system of sucking pests. Despite claims that FPF is potentially “bee-safe” by risk assessments, laboratory data have suggested that FPF has multiple sub-lethal effects on individual honey bees. Our study aimed to expand the studies to the effects of field-realistic concentration of FPF. We found a statistically significant decrease in the survival rate of honey bees exposed to FPF, whereas there were no significantly negative effects on larvae development durations nor foraging activity. In addition, we found that the exposed foragers showed significantly higher expression of ApidNT, CYP9Q2, CYP9Q3, and AmInR-2 compared to the CK group (control group), but no alteration in the gene expression was observed in larvae. The exposed newly emerged bees showed significantly higher expression of Defensin and ApidNT. These results indicate that the chronic exposure to the field-realistic concentration of FPF has negligible effects, but more important synergistic and behavioral effects that can affect colony fitness should be explored in the future, considering the wide use of FPF on crops pollinated and visited by honey bees.