Scientists Discover Pesticide Impacts Bumblebee Size

Pesticides may be able to fend off irritating insects, but they can also impact helpful ones--like bumblebees. Now, scientists have discovered that exposure to a widely used pesticide causes worker bumblebees to grow less and then hatch out at a smaller size.

The pesticide in question is called the pyrethroid pesticide. It's widely used on flowering crops to prevent insect damage. In order to find out exactly how this might affect bumblebees throughout their lives, though, the researchers worked with colonies of bumblebees in their laboratory. They exposed half of the bees to the pesticide and left the other half alone. Then, they tracked how the bee colonies grew over a four month period. They recorded their size and weighed the bees in micro-scales. In addition, they monitored the number of male bees and queens produced by each colony.

"We already know that larger bumblebees are more effective at foraging," said Gemma Baron, one of the researchers, in a news release. "Our result, revealing that this pesticide causes bees to hatch out at a smaller size, is of concern as the size of workers produced in the field is likely to be a key component of colony success, with smaller bees being less efficient at collecting nectar and pollen from flowers."

Currently, there's an European Union moratorium on the use of three neonicotinoid pesticides. This means that the use of other classes of pesticide, including pyrethroids, is likely to increase. Needless to say, this could greatly affect bumblebee colonies' ability to survive.

"Bumblebees are essential to our food chain so it's critical we understand how wild bees might be impacted by the chemicals we are putting into the environment," said Mark Brown, one of the researchers, in a news release. "We know we have to protect plants from insect damage but we need to find a balance and ensure we are not harming our bees in the process."

The findings are published in the Journal of Applied Ecology.