Sulfoxaflor Impairs Bumblebee Memory Across Moderate and Extreme Temperatures

Pesticide exposure and climate change are key drivers of pollinator declines. Exposure to certain pesticides and high temperatures can influence the cognitive ability of insect pollinators, such as bees, but little is known about how these stressors interact. As central place foragers, bees must learn and remember floral cues, and so impaired memory may influence foraging efficiency and fitness. While individual exposure to specific pesticides and high temperatures can impair bee memory, the interactions between these two key stressors remain poorly understood. Here, using a free-moving proboscis extension reflex experimental design, we assessed the impact of an acute, field-realistic dose of the insecticide sulfoxaflor on bumblebee (Bombus terrestris ) memory across a range of environmentally relevant temperatures (12°C-36°C). We found that exposure to sulfoxaflor impaired bumblebee memory, despite the study using a pesticide dose that could be experienced during a single foraging event, rather than a prolonged chronic exposure regime. In contrast to previous findings, we found no impact of temperature exposure on bumblebee memory and no significant interaction between sulfoxaflor exposure and temperature. Our results, alongside previous research, demonstrate that sulfoxaflor can have negative sub-lethal impacts on important pollinators. Legislation that either (i) restricts the outdoor use of sulfoxaflor entirely, as seen in the EU, or (ii) limits use to non-flowering crops, will benefit pollinators, and limit the unintended consequences of intensive agriculture.