Environment: Are pesticides making bumblebees dumber?

Bumblebee butt and thistle.
Bumblebees may struggle to navigate wild flowers after exposure to pesticides. @bberwyn photo.

Study shows even low levels of neonicotinoids affect foraging skills

Staff Report

There’s more evidence showing how exposure to pesticides affects bumblebees. In anew study, scientists found that low levels of pesticides can affect which flowers bumblebees choose and potentially hindering their ability to forage for nectar and pollen.

The findings were published in the journal Functional Ecology and will help inform the use of pesticides in agriculture. The research is important because bees and other insects pollinate many of the world’s important food crops and wild plants. But pollinators are declining due to a variety of causes, showing the need for more research and safeguards.

In the study, bumblebees exposed to a realistic level of a neonicotinoid insecticide (thiamethoxam) collected more pollen but took longer to do so than control bees. Pesticide-exposed bees also chose to forage from a different flower in comparison to control bees.

“Bees rely on learning to locate flowers, track their profitability and work-out how best to efficiently extract nectar and pollen,” said¬†Professor Nigel Raine, with the University of Guelph (Canada). “If exposure to low levels of pesticide affects their ability to learn, bees may struggle to collect food and impair the essential pollination services they provide to both crops and wild plants.”

Previous studies have found that exposure to neonicotinoid pesticides can cause changes in the brain, more specifically in the areas associated with learning and memory in honeybees.

In this new study, the researchers found that, while bumblebees exposed to pesticides collected more pollen than control bees, control bees were able to learn how to manipulate these complex flowers after fewer visits.

Dr Dara Stanley, Royal Holloway University of London, lead author of the study, said: “Bumblebees exposed to pesticide initially foraged faster and collected more pollen. However unexposed (control) bees may be investing more time and energy in learning. Our findings have important implications for society and the economy as pollinating insects are vital to support agriculture and wild plant biodiversity.”

“Our results suggest that current levels of pesticide-exposure could be significantly affecting how bees are interacting with wild-plants, and impairing the crucial pollination services they provide that support healthy ecosystem function,” Raine added.

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