The way bumblebees get pollen from wildflowers changes when the insects are exposed to commonly used neonicotinoid pesticides according to new research at the University of Guelph.

The pesticides "modify the way in which information flows through the nervous system," said researcher Nigel Raine, who is also the Rebanks Family Chair in pollinator conservation..

"In this study, we found differences in foraging preferences ... and we found some results that suggest that it's affecting their ability to learn how to handle the flowers," he said. "That might affect their ability to visit more flower species and to provide effective pollination services to these wild plants."

'Sublethal exposure' to pesticides affects bees

The fieldwork for the study was completed by Dara Stanley of Royal Holloway University of London in the United Kingdom.

Stanley and Raine discovered that when bees were exposed to thiamethoxam – a neonicotinoid pesticide that is commonly used on crops in North America – they collected pollen more often than bees that had not been exposed. However, the bees that had not been exposed learned how gather pollen more efficiently than their counterparts.

Neonicotinoid exposure also appeared to affect a bees preference for certain flowers. Bees that had been exposed tended to pick lotus corniculatus, a flowering plant in the pea family, while bees that had not been exposed tended to pick clover flowers.

Bumblebee

Exposure to pesticides can affect how bumblebees forage for pollen, a new study involving University of Guelph researcher Nigel Raine has shown. (Matthias A. Fürst)

"Our results suggest that the foraging behaviour of bumblebees on real flowers can be altered by sublethal exposure to field-realistic levels of pesticide," Stanley and Raine wrote in their study, which was published Monday in the journal Functional Ecology.

"This has implications for the foraging success and persistence of bumblebee colonies ... and ability of bees to deliver the crucial pollination services to plants necessary for ecosystem functioning."

Research relevant in Canada

Although the research was completed in the U.K., Raine said the results are relevant in Canada. The pesticide they studied is used worldwide, and while the bumblebee species differ by country, they have similar foraging habits.

Raine said the study is also noteworthy because it is focused on bumblebees. Most studies on the impact of neonicotinoids involve honeybees.

"We're interested in looking at bumblebees because they're important wild and manage pollinators and they're a gateway to getting a broader picture on lots of different types of bees," Raine said.

"In Canada, we have something like 825 species of bee. There's one honeybee, there's about 30 bumblebees and the rest are solitary bees."

He said basing the impacts of neonicotinoid use on the behaviour of "one very a-typical bee like the honey bee is, perhaps, not the best way to look at things."