London - A controversial but widely used pesticide poses a substantial risk to wild bees according to two independent studies.
The largest outdoor field trial yet into neonicotinoid pesticide found it has a significant impact on the ability of wild bumblebees to form colonies, and on solitary bees to build their nests.
A separate laboratory study discovered that bumblebees cannot taste neonictinoid-laced sugar solution and so are unable to avoid the pesticide. The scientists also found that bumblebees seem to prefer toxin-laced nectar to food untainted with neonics, possibly because of the drug-like effects on the insect's brain.
"Bees can't taste neonicotinoids in their food and therefore do not avoid them. This is putting them at risk of poisoning when they eat contaminated nectar," said Professor Geraldine Wright, of Newcastle University, who led the study published in Nature.
"Even worse, we now have evidence that bees prefer to eat pesticide-contaminated food. Neonicotinoids target the same mechanisms in the bee brain that are affected by nicotine in the human brain," Professor Wright said.
"The fact that bees show a preference for food containing neonicotinoids is concerning as it suggests that like nicotine, neonicotinoids may act like a drug to make foods containing these substances more rewarding," she said.
The outdoor experiment on wild bees took place in southern Sweden and involved 16 fields of rapeseed, eight of which were planted with crops where the seeds were treated with Eldo, a pesticide containing the neonicotinoid clothianidin, made by the German company, Bayer.
"The most dramatic result we found was that bumblebee colonies almost didn't grow at all at the clothianidin-treated sites compared to the control sites," said Maj Rundlof, of Lund University in Sweden, the lead author of the study.
The EU ordered a Europe-wide moratorium on the use of neonicotinoids for flowering crops two years ago, which is to be reviewed at the end of this year. The UK, however, has taken a more relaxed view of the pesticide, based on its own scientific advice.
The Independent