The studies did not link the pesticides to the collapse of whole bee colonies, but did raise enough issues to lead to a vote last month for a two-year precautionary ban by the European Commission (EC). The ban was blocked, temporarily, by Germany, Britain and seven other countries, citing evidence that neonicotinoids were not the sole or likely the primary culprit, and their impact still is unclear. The EC plans an appeal.

Last year, one study showed that bumblebees exposed to high doses of the neonicotinoid imidacloprid in the laboratory, then released to forage in the field, had sharply reduced colony growth rates and produced 85 percent fewer queens to found new colonies.

In another study, more than 30 percent of free-ranging honey bees whose brains were doused with the neonicotinoid thiamethoxam — which is not the way bees encounter the chemical in the real world — got confused, failing to return to the hive.

The results were so dramatic and so contradictory of real life experience of some beekeepers in Canada, Europe and Australia who use neonicotinoids and where many bee colonies are thriving that the United Kingdom’s Department for Environment, Food and Rural Affairs (DEFRA) decided to re-evaluate existing research.

The agency pointed to the problem with much of the laboratory-based data — it measures doses and application methods not used by farmers.

“The risk to bee populations from neonics, as they are currently used, is low,” DEFRA concluded in March.

“Laboratory-based studies demonstrating sub-lethal effects on bees from neonics did not replicate realistic conditions, but extreme scenarios … While this assessment cannot exclude rare effects of neonicotinoids on bees in the field, it suggests that effects on bees do not occur under normal circumstances. Consequently, it supports the view that the risk to bee populations from neonicotinoids, as they are currently used, is low.”

As the British Bee Keeper Association recently warned, rushing to ban neonicotinoids, when the evidence remains contradictory, could well do more damage than good, as other pesticides, some known to be more harmful to bees, would of necessity be re-introduced.

The Forbes article is at www.forbes.com/sites/jonentine/2013/04/11/science-collapse-disorder-the-real-story-behind-neonics-and-mass-bee-deaths.