As the European Union prepares to restrict the use of neonicotinoid pesticides, suspected by some of at least contributing to the phenomenon of Colony Collapse Disorder (CCD), Bayer is focusing on the parasitic mite Varroa destructor as a primary culprit.

At a recent meeting of beekeepers and bee scientists, the company reported on a five-year field study with 2,500 beehives conducted in cooperation with the Bee Research Institute of Frankfurt University. The results, Bayer said, show that the varroa mite can quickly re-infest bee colonies that were successfully treated, meaning that careful colony management is needed.

In addition to reducing re-infestation in late summer, because the mite is still a moving target, an integrated pest management approach is necessary, Bayer said. It recommends sustained treatment with its own acaricide products containing polymer matrix carriers, along with an annual rotation of products with different modes of action to prevent adaptation of the mites to the active ingredients.

From the upcoming winter planting season, the European Commission has restricted the use of neonicotinoid pesticides, in the main the clothianidin and imidacloprid products made by Bayer and thiamethoxam products made by Swiss rival Syngenta, on all crops except winter cereals and plants not attractive to bees, such as sugar beet.