Research funded by the UK government and published on Monday suggests that exposure to low levels of pesticides can impact the foraging behaviour of bumblebees.

Researchers from the University of Guelph, Canada and Royal Holloway in London found that even low levels of pesticides can change bees’ preference of wildflowers and hindering their ability to learn new skills needed to extract nectar and pollen. The study looked at common wildflowers that have complex shapes such as white clover and bird’s foot trefoil.

Though both wild and domestic bees play a hugely important role in corp pollination around the world, the vital insects are experiencing rapid declines across the northern hemisphere, believed to be the result of a combination of factors, including disease, climate change, habitat loss for wild bees and exposure to certain pesticides. However, though the limited evidence available suggests these factors are affecting wild bees like bumblebees as well as domesticated honeybees, most studies have focused on honeybees.

In the new research, Professor Nigel Raine, Rebanks Family chair in pollinator conservation and a visiting professor at Royal Holloway, and Royal Holloway’s Dr Dara Stanley found bumblebees exposed to a realistic level of a neonicotinoid insecticide (thiamethoxam - one of three neonics subject to a partial ban by the EU Commission) 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.

Prof Raine said, “Bees rely on learning to locate flowers, track their profitability and work out how best to efficiently extract nectar and pollen. 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 also found that exposure to neonicotinoid pesticides can cause changes in the brain, more specifically in the areas associated with learning and memory in honeybees. The key finding in this latest study is 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.

The study was funded by Defra, agricultural research council BBSRC, the Scottish government and the Wellcome Trust. Lead author Dara Stanley, of Royal Holloway University of London, explained, “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.”

Raine said there is an increasing need for field-realistic research into the impact of all pesticides on bumblebees and other wild pollinators.

“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,” he said.