Pesticide exposure impairs the flight performance of bees

Researchers at Imperial College London are reporting that bees exposed to a neonicotinoid pesticide are only able to fly one-third of the distance covered by unexposed bees. Reduced flight performance affects the foraging ability of the bees, and may cause colonies to end up with inadequate amounts of food.

Foraging bees are essential pollinators for crops and wildflowers, and weakened flight ability can compromise these crucial pollination services.

The current study found that small doses of the neonicotinoid imidacloprid – levels that would be encountered in fields – caused bees to fly significantly shorter distances and for less time than bees who were not exposed to the pesticide. The toxic exposure reduced the area in which colonies could forage by up to 80 percent.

Just after the bees encountered imidacloprid, they appeared to enter a hyperactive state during which they flew much faster and likely wore themselves out, according to the researchers.

“Neonicotinoids are similar to nicotine in the way they stimulate neurons, and so a ‘‘rush’ or hyperactive burst of activity does make sense,” explained study first author Daniel Kenna. “However, our results suggest there may be a cost to this initial rapid flight, potentially through increased energy expenditure or a lack of motivation, in the form of reduced flight endurance.”

“Our findings take on an interesting parallel to the story of the ‘Tortoise and the Hare.’ As the famous fable states, ‘slow and steady wins the race’. Little did Aesop know that this motto may be true for bumblebees in agricultural landscapes. Just like the Hare, being speedier does not always mean you reach your goal quicker, and in the case of bumblebees, exposure to neonicotinoids may provide a hyperactive ‘buzz’ but ultimately impair individual endurance.”

Study lead author Dr. Richard Gill is a researcher in the Department of Life Sciences at Imperial.

“Previous studies from our group and others have shown that bee foragers exposed to neonicotinoid pesticides bring back less food to the colony. Our study on flight performance under pesticide exposure provides a potential mechanism to explain these findings,” said Dr. Gill.

“The negative effects of pesticide exposure on flight endurance have the potential to reduce the area that colonies can forage for food. Exposed foraging bees may find themselves unable to reach previously accessible resources, or incapable of returning to the nest following exposure to contaminated flowers.”

“Not only could this reduce the abundance, diversity, and nutritional quality of food available to a colony affecting its development, but it could also limit the pollination service bees provide.”

The study is published in the journal Ecology & Evolution.

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By Chrissy Sexton, Earth.com Staff Writer