Pyrethroid Pesticide Use Linked with Reduced Size of Worker Bumble Bees

Pesticide use is shrinking worker bumblebee size, according to a new study.

Royal Holloway University of London researchers have found that worker bumblebees are getting smaller and hatching earlier than they should, thanks to increased use of pyrethroid pesticide. The chemical is used to prevent bugs from damaging flowering plants.

For the study, researchers exposed half of a bumblebee population to the pesticide. The team then tracked the growth of these bees over a four-month period. Microscales were used to measure the weight of a bee. Also, researchers kept a track of all the new bees produced in the colony.

"We already know that larger bumblebees are more effective at foraging. 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," said researcher Gemma Baron from Royal Holloway, according to a news release.

Pyrethrins are a class of botanical insecticides derived from chrysanthemum flowers. These chemicals work by altering nerve function of insects. Pyrethroids are synthetic insecticides that have the same structure and function as pyrethrins.

The study is published in the Journal of Applied Ecology.

Why Worry About Bees?

The current study shows the effects of a chemical over the entire life cycle of bumble bees. The research will be presented at a national Bee Health Conference that will take place in London from 22 to 24 January 2014.

"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. 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," Mark Brown, Royal Holloway researcher.

There are about 4,000 species of bees in North America. These insects are known for their role in pollination - about 90 percent plants require bugs to pass their pollen.

There has been a recent decline in the bee population around the world and experts say that loss of bees could threaten global agriculture. A recent study had showed that loss of just one species of bees can reduce the reproduction success of plants.