A new large-scale study of neonicotinoid-based insecticides has demonstrated that the use of this common pesticide is causing damage to honeybee colonies. This is the first in-field study of the effects of the substance on bees, with previous studies being lab-based.

This new study was conducted across 33 farmland sites in the UK, Germany and Hungary, where the health of honeybees, bumblebees and solitary bees living by rapeseed fields both treated and untreated by insecticides were measured. Bee colonies in the UK and Hungary were affected by the insecticides, while bees in Germany saw less of an impact: it was found that the German bees were foraging less in the affected fields, collecting only about 15 percent of their food from there, compared to the 40-50 percent gathered by their UK and Hungarian counterparts. Overall, reproductive difficulties within the colonies increased along with their level of exposure to the pesticides. The research team also found that the bees were being affected by pesticides that weren’t part of the study, but were residues left over from past treatments of the fields.

"We showed significant negative effects at critical life cycle stages," explains research team member professor Richard Pywell, with the UK’s Centre for Ecology and Hydrology (CEH). "If the bees are foraging a lot on oil seed rape, they are clearly at risk. This is a large and important piece of evidence, but it is not the only evidence regulators will look at."

Interestingly, the study was funded by Syngenta and Bayer, companies that sell the two neonicotinoid compounds –a product that makes up a quarter of the multi-billion dollar pesticide market — although the companies were not involved in the design and execution of the study. Both companies are dismissing the study’s findings, claiming that they’re too simplistic and show inconsistent results, but CEH researchers, and the scientific community involved in peer-reviewing the study, stand by their findings. According to Pywall:

"We stand by our peer-reviewed paper. We undertook the statistical analysis and reported the findings as we saw them and those are underpinned by the data. We are absolutely independent."