Research from the UK Food and Environment Research Agency (FERA) has cast doubt on links between bee population declines and a class of insecticides called neonicotinoids.

‘Neo-nics’ have been a controversial topic of late. In January, Europe’s food-safety body said that they may pose a risk to honeybees, but an attempt to ban the use of three such compounds — clothianidin, imidacloprid and thiamethoxam — across the European Union hit roadblocks this month when it was rejected in a vote by member states. Campaigners hope that ending the use of these compounds could help to arrest declines seen in some bee populations across the globe.

Now, a field trial run by FERA, based in Sand Hutton, has failed to find any “clear consistent relationship” between neonicotinoid residues and the size of bumblebee colonies or the number of new queens they produce. “The absence of these effects is reassuring but not definitive,” says the FERA study, which involved assessing the health of colonies near crops grown from seeds that were treated with clothianidin and imidacloprid.

A related publication, also released this week, by the UK Department for Environment, Food and Rural Affairs (DEFRA), which funds FERA, summarizes the data and concludes that there is a “growing body of evidence” that neonicotinoids do not exert an effect under conditions where bees can forage naturally. This suggests that studies in the laboratory that have linked the insecticides to an impact on bee health at less-than-lethal doses “did not replicate realistic conditions, but extreme scenarios”, says the DEFRA report, which summarizes evidence on the purported link.

DEFRA’s conclusion is likely to prove highly controversial. Campaigners have been pushing for Europe to enact a ban on neo-nics and have condemned the UK government for not supporting this.

In a recent World View in Nature, Lynn Dicks, a conservation researcher at the University of Cambridge, UK, wrote: