Exposure to neonicotinoid compounds, the world’s most commonly used insecticides, directly impacts the social behavior of bumblebees, causing them to be less active and less likely to care for or feed larvae, according to a new study published in the journal Science.
The research, led by biologist James Crall at Harvard University, used tiny, automated robotic platforms to monitor activity in several bumblebee colonies after exposure to “field-realistic levels” of imidacloprid, a common neonicotinoid, dissolved in artificial nectar. Previous studies have shown that neonicotinoids contribute to the shrinking of bee colonies, but exactly why that happens has long evaded scientists.
Crall and his colleagues found that the impacts of the neurotoxin pesticide on bees’ nursing activity and social behavior were greater at night, possibly related to the daily patterns of the neonicotinoid’s application. The scientists also found that exposure to imidacloprid impaired a bee colony’s thermoregulation, hindering the bees’ construction of an insulating wax canopy.
Due to mounting scientific evidence linking neonicotinoids to the decline of bees and other pollinators, the European Union announced a ban on all outdoor uses of the class of pesticides earlier this year. Farmers in the EU, however, will still be able to apply them to plants grown inside greenhouses.
Watch: Automated tracking of nest workers in a bumblebee colony. [Credit: James Crall]