Europe's largest field research on pesticides has proven that neonicotinoids used for agricultural purposes may be detrimental both to honey and wild bees. The monitoring has lasted for 2 years, encompassing 33 agricultural sites in the territories of Great Britain, Hungary and Germany.
The research was described in detail in Science scientific magazine, having clearly shown that insecticides may, in some cases, be toxic not only for pests, but also bees. "We learn again: It's complicated", comments Tjerd Blacquiere, a biologist of Wagenigen University in the Netherlands.
Neonicotinoids have recently become very popular, making up the world's most preferably used class of pesticides. Such popularity of these compounds had been contributed to by the increasing resistance to other substances of this kind demonstrated by insects. Neonicotinoids form coats on seeds, protecting them from pests that are present in soil. Finally, they also run across to nectar and pollen which poses risks to pollinators.
Lab tests have shown that even low doses thereof cause diorientation in bees, while the European Union precautionary put a moratorium on 3 types of neonicotinoids in 2013. In order to confirm the harmfulness of these compounds in natural environment, there were trials on rapeseed exposed to clothianidin and thiamethoxam, conducted in three countries. While there was no permanent effect on bee colonies determined in Germany, the case of Hungary has shown that the number of workers became 24% lower on average with regard to the rapeseed protected by clothianidin there a year after these trials had been conducted. Trials carried out in Great Britain have yielded similar results. However, Richard Pywell, an ecologist, is of the opinion that the German bee colonies might have been more pesticide-resistant due to the fact that the presence of wildflowers surrounding the fields there could influence their immunity by providing them with more nutritional diversity. At the same time, it is claimed that wild bees are more vulnerable to pesticides than honey bees. The decline in their number has been correlated with the level of chemicals found in their nests. It has also been noticed that neonicotinoids have a tendency for retention in natural environment, as well as that they may have negative effects on it later on. Similar research was also conducted in Canada, having lasted for 4 months overall. "The risks of neonicotinoids have been understated in the past and the benefits have been overstated", concludes Jeremy Kerr of the University of Ottawa.
The lead researcher dealing with the bee care at Bayer CropScience company does not consider it as any reason for immediate concern, holding that the products utilised are safe for bees. Nevertheless, Health Canada proposed the withdrawal of imidacloprid from sale last year, as based on the risk to acquatic insects it could pose, while the European Commission is considering to extend the moratorium with regard to all extra-greenhouse grown crops. This clearly indicates the doubtful safety of use of the pesticides of this kind.