Sublethal neonicotinoid exposure attenuates the effects of electromagnetic fields on honey bee flight and learning

•The effects of electromagnetic fields (EMFs) and clothianidin on bees were studied.•Combined impacts of these stressors on honeybee flight and learning were measured.•EMF exposure alone increased honeybee wingbeat frequency for treatments above 100µT.•EMF exposure alone reduced honeybee learning success in proboscis extension assays.•Clothianidin exposure attenuated the effects of EMFs on honeybee learning and flight. Many environmental stressors are currently implicated in the decline of flying insects in general, and important pollinator species such as the honey bee. Recent studies have shown that extremely low frequency electromagnetic fields (ELF EMFs) affect many aspects of insect behaviour and cognition which raises the potential that ELF EMFs could interact with other environmental stressors such as neonicotinoid insecticides to have even greater impact on the decline of flying insects. Here we analysed the effects of individual and combined exposure of the honey bee to 50 Hz EMFs and sublethal exposure to clothianidin, in a tethered flight assay and an olfactory appetitive learning assay. Clothianidin was significantly toxic to bees and exposure to field-realistic levels (2.00 ng/bee) led to 25% mortality. Exposure to ELF EMFs alone led to a significant increase in wingbeat frequency at levels above 100 µT. Prior exposure to clothianidin attenuated the effects of EMFs on wingbeat frequency. Exposure to EMFs alone reduced learning of a proboscis extension reflex (PER). Prior exposure to low doses of clothianidin attenuated the effects of EMFs on PER. These results indicate no evidence of synergy between clothianidin and ELF EMFs as environmental stressors but suggest the potential for EMFs to affect the same susceptible fraction of the bee population that have been affected by clothianidin. Results lay the foundation to further explore the interactions of ELF EMFs with other environmental stressors and consider the key factors that may make bees susceptible to ELF EMFs.