Honeybees are avoiding any significant damage from neonicotinoid insecticides according to an academic review of all in-field research carried out so far.

With the European Commission’s two-year ban on neonicotinoids to be reviewed soon, and new trial data about to be published, a number of academics were asked to study the current data.

“The evidence so far points to a lack of effect on honeybee colonies from neonicotinoids,“ Professor Charles Godfray, Oxford University Professor of Entomology, told a news briefing.

See also: Four counties to be granted access to neonicotinoids

He and his colleague Prof Angela McLean were two of the academics asked by the UK’s chief scientific adviser, Sir Mark Walport, to review the data as the European Commission (EC) considers whether to extend the ban.

The EC imposed a ban in December 2013 on three neonicotinoids that were used as seed dressing on bee-attractive crops such as oilseed rape, due to their perceived harmful effect on bees.

Prof Godfray said although there was no field data so far to show neonicotinoids had any effect on honeybee colonies, a Swedish study led by Dr Maj Rundlof had shown they have a harmful effect on bumblebees.

But as regards to neonicotinoids having a damaging effect on honeybees in the field, Prof Godfray said so far they had found “no smoking gun” linking the two.

He points out that neonicotinoids can give sub-lethal doses to honeybees in the field, but it is unclear whether this is pushing down honeybee numbers.

A major factor behind the decline in bee numbers is habitat changes, and the role of neonicotinoids is unclear, he added.

He and Prof McLean are members of the Oxford Martin School, a research arm of Oxford University, and they were asked to review more than 400 scientific papers on the topic. Prof McLean said they looked to act as an “honest broker” to give a summary.

The EC ban covers three neonicotinoids – clothianidin, used in Bayer CropScience’s Modesto, thiamethoxam, used in Syngenta’s Cruiser, and also imidacloprid.

The seed dressings were used to control cabbage stem flea beetle and without the treatment, 3.5% of the nation’s oilseed rape crop was lost to the pest in autumn of 2014, according to an AHDB survey.

This season, growers in four flea beetle hotspot counties – Suffolk, Cambridgeshire, Bedfordshire and Hertfordshire – were allowed to use neonicotinoids on up to a maximum of 30,000ha or about 5% of the national crop.

The UK government has always opposed the EC ban, as has the agrochemical industry, which has agreed to fund an independent trial run by the Centre for Ecology and Hydrology, due to be published before Christmas.

The summary of recent evidence surrounding neonicotinoids and bees is published in the journal Proceedings of the Royal Society B.