Bee flower choices are altered by exposure to pesticides: U of Guelph

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Low levels of pesticides can impact the foraging behaviour of bumblebees on wildflowers, changing their floral preferences and hindering their ability to learn the skills needed to extract nectar and pollen, according to a study co-authored by Prof. Nigel Raine, School of Environmental Sciences.

The study, published in Functional Ecology, is the first to explore how pesticides may impact the ability of bumblebees to forage from common wildflowers that have complex shapes such as white clover and bird’s foot trefoil.

Bees and other insects pollinate many of the world’s important food crops and wild plants, raising serious concerns about the impacts of reported global pollinator declines on food security and biodiversity.

The researchers found that 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 than control bees.

“Bees rely on learning to locate flowers, track their profitability and work out how best to efficiently extract nectar and pollen,” says Raine. “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.

“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,” says Raine.