UC San Diego

Insecticides pose a major health concern for honey bee colonies, particularly those involved in crop pollination. Flupyradifurone (commercially known as Sivanto) is a new butenolide insecticide that has been marketed as bee-safe, and is especially used in cases where pest insects have evolved resistance to neonicotinoid pesticides. In addition to insecticides, honey bee health is also affected by decreases in food source diversity and quality, as can happen in agricultural monocultures. We tested the effects of flupyradifurone exposure and food quality (sucrose concentration) on European honey bee flight performance and mortality. Flight performance is critical to colony health because flight is required for worker bees to forage for food and to return safely to the nest. At our field site, bees flew to collect pollen and nectar throughout the year; we therefore analyzed FLU effects in the winter and the summer. We found that a high-quality sucrose diet increased survival in foragers (p<0.0001) over the winter and summer. Exposure to FLU caused bees to consume less of the high-quality sucrose diet in summer (p<0.05), and bees that consumed low-quality sucrose ingested more FLU than bees that consumed high-quality sucrose (p<0.0001). Control foragers flew longer (p=0.029) and farther (p=0.046) in the summer than in the winter. However, FLU consumption eliminated these seasonal differences in flight duration and distance. FLU also significantly decreased the percentage of successful flights when bees consumed low-quality 33% sucrose (p=0.0013). Higher quality sucrose significantly increased the temperature difference between thoracic temperature before flight—a measure of wing muscle temperature—and ambient air temperature (∆T before flight). Thoracic temperature (T before flight) was positively, though weakly, correlated with flight velocity (p≤0.027). Because agricultural insecticide exposure and poor nectar quality can co-occur, we suggest that further studies are necessary to evaluate the safety of FLU for honey bees.