Exposure to pesticides leads to a slowdown in the flight of bumblebees

Bees exposed to a neonicotinoid pesticide only travel a third of the distance that unexposed bees are able to reach.

Flight behavior is crucial in determining the fodder pattern of bees. Therefore, reduced flight performance in the event of exposure to pesticides could result in colony starvation and affect pollination services.

Bees in search of food are essential pollinators for the crops we eat and the wildflowers in our countryside, gardens and parks. Any factor compromising the flight performance of bees could therefore have an impact on this pollination service.

A study by researchers from Imperial College London, published today in the journal Ecology and Evolution, reveals how exposure to a common class of neurotoxic pesticides, a neonicotinoid, reduces individual flight stamina (distance and duration) in bumblebees.

The study shows that bees exposed to the neonicotinoid imidacloprid at doses encountered in the fields travel much shorter distances and last less time than unexposed bees, which could reduce by 80% the area in which colonies can to eat.

Curiously, the exposed bees appeared to enter a hyperactive state in which they initially flew faster than the unexposed bees and could therefore be "exhausted".

The first author of the study, Daniel Kenna, of the Department of Life Sciences at Imperial, said: "Neonicotinoids look like nicotine in the way they stimulate neurons." An intense activity "or a surge of hyperactive activity therefore makes sense.

However, our results suggest that this first rapid flight could have a cost, potentially due to increased energy expenditure or lack of motivation, in the form of reduced stamina.

"Our results are an interesting parallel with the story of" The Turtle and the Hare. "As the famous fable puts it," slowly and steadily wins the race. "Aesop did not know that this motto could be true for bumblebees in agricultural landscapes Just like the hare, being faster does not always mean that you reach your goal faster and, in the case of bumblebees, exposure to neonicotinoids can create a hyperactive "buzz" but ultimately , detract from individual endurance. "

The team tested the flight of bees using an experimental "air mill", a spinning device with long arms attached to magnets. The bees had a small metal disk attached to the back, which allowed the researchers to temporarily attach the bees to the magnetic arm. As bees flew in circles, the team was able to accurately measure distance traveled and speed in a controlled environment.

Lead author, Dr. Richard Gill, also of the Imperial Life Sciences Department, commented: "Previous studies by our group and others have shown that bee-foragers exposed to Neonicotinoid pesticides yield less food to the colony.Pesticide exposure provides a potential mechanism to explain these results.

"The negative effects of pesticide exposure on flight resistance may potentially reduce foraging grounds for colonies." Exposed forage bees may be unable to access resources. previously accessible or unable to return to the nest after being exposed to infected flowers.

"Not only could it reduce the abundance, diversity and nutritional quality of the food available to a colony that would affect its development, but it could also limit the pollination services provided by bees."