Chronic exposure of bumblebees to agricultural pesticides impairs natural foraging behaviour, which has a knock-on effect on brood care and colony productivity. These observations are made in Nature this week and have clear implications for the conservation of insect pollinators in areas of agricultural intensification. They hint that existing guidelines for testing the toxicity of pesticides on bees may be insufficient.
As bees are crucial pollinators, contributing to around 80% of insect pollination, it is important to understand and mitigate the causes of current declines. Exposure to pesticides has been shown to affect bee behaviour and has been associated with colony declines; bees frequently encounter neonicotinoid pesticides when foraging on flowering crops.
Richard Gill and co-workers establish a link between the effects on individual bees and the success of the colony by exposing bumblebee colonies to neonicotinoid and pyrethroid pesticides at levels found in the field for 4 weeks. They also find that exposure to the combination of pesticides increases the propensity of colonies to fail.
Current guidelines only test the effects of pesticides on bees for up to 96 hours, and do not consider exposure to multiple pesticides, despite this being common in the field. Gill and colleagues say that their results emphasize the importance of performing longer tests and investigating the effects of combined exposure when assessing the risks of pesticide use.