A novel insecticide (flupyradifurone) negatively impacts bumblebee (Bombus impatiens) reproduction

Restrictions and bans on the use of neonicotinoid pesticides are becoming more common worldwide, in part due to their detrimental sub-lethal effects on pollinators. Novel insecticides, such as flupyradifurone, are now replacing neonicotinoids in many cases, yet assessing their sub-lethal effects on bees is not required to be registered for use in the United States. We assessed the effects of chronic exposure to flupyradifurone on bumblebee (Bombus impatiens) sucrose intake and reproduction within replicated experimental microcolonies. Using three levels of field realistic concentrations, we found that microcolonies exposed to the two higher concentration levels had impaired reproduction. Specifically, we found significantly fewer fourth instar larvae and lower total larval mass produced, despite no significant difference in the total number of larvae produced or the latency to initiate egg laying, consistent with flupyradifurone exposure leading to larval death at a concentration of 1.6ppm. We also found that at the highest field-realistic concentration, bees consumed less sucrose solution, and stored significantly less in their honeypots. Our results indicate that flupyradifurone will likely have negative impacts on native bees such as bumblebees. More broadly, we argue that the sub-lethal effects of novel insecticides on non-Apis bees need to be included as a standard part of the pesticide regulatory process.