Popular pesticide leaves honey bees vulnerable to deadly mites

A commonly used class of pesticides may be preventing bees from properly grooming themselves, leaving them vulnerable to deadly mites, according to a new study out of the University of Guelph. This milestone research is the first to associate the behavioral change with neonicotinoid pesticides, highlighting yet another concerning issue that may influence future limitations on the product's use.

Bee-killing pesticides present a substantial risk to pollinators, and so it's no surprise that modern agriculture has been linked to global declines in bee populations. Of particular concern are neonicotinoids, a class of pesticides that first entered development in the 1980s. The products are used due to their lower toxicity to birds and mammals compared to organophosphate and carbamate, but experts have raised concerns about neonics' risk to bees.

According to the new study out of the University of Guelph, neonicotinoid pesticides have been linked to honey bees and an their impaired ability to groom. This behavior is necessary in order to remove varroa mites, which can infect honey bees and potentially transmit deadly viruses to the pollinators.

In addition to potentially transferring viruses, the mites threaten bee colonies by leeching off the insects' blood supply and body fat. Bees are only able to rid themselves of these mites by frequently, and quite enthusiastically, grooming.

Honey bees regularly exposed to low doses of clothianidin, a neonicotinoid pesticide, displayed decreased grooming behaviors, however, revealing a potential factor contributing to global bee colony declines. The bees were exposed to sub-lethal pesticide doses akin to what they may experience in crop fields.

The lowest dose administered was associated with a significant drop in overall grooming, while a medium dose was only found to impact grooming in bees that had been exposed to varroa mites. The research arrives amid Canada's possible new limits on the use of certain neonicotinoids.