UC San Diego

Flupyradifurone (FPF, Sivanto®) is a new butenolide insecticide that, like the neonicotinoids, is a systemic nicotinic acetylcholine receptor (nAChR) agonist. However, FPF is considered bee-safe (according to standard Risk Assessment tests), and is thus a potential solution to the adverse effects of other pesticides on beneficial insects. To date, no studies have examined the impact of nutritional stress (decreased food diversity and quality) and FPF exposure on bee health although both stressors can occur, especially around agricultural monocultures. We therefore tested the effects of a field-realistic FPF concentration (4 ppm, FPF_{daily dose} = 241 ± 4 ng/bee/day, 1/12 of LD₅₀) and nutritional stress (nectar with low-sugar concentrations) on honey bee (Apis mellifera L.) mortality, food consumption, thermoregulation, flight success (unsuccessful vs. successful), and flight ability (duration, distance, velocity). Flight and thermoregulation are critical to colony health: bees fly to collect food and reproduce, and they thermoregulate to increase flight efficiency and to rear brood. We studied the effects across seasons because seasonality can influence bee sensitivity to environmental stress. We demonstrate that, depending upon season and nutritional stress, FPF can reduce bee survival (-14%), food consumption (-14%), thermoregulation (-4%, i.e. hypothermia), flight success (-19%), and increase flight velocity (+13%). Because pesticide exposure and nutritional stress can co-occur, we suggest that future studies and pesticide risk assessments consider both seasonality and nutritional stress when evaluating pesticide safety for bees.