The control of infestations by the parasitic mite Varroa destructor in honey bee colonies can significantly reduce the spread of the deformed wing virus (DWV) among other wild pollinators, according to a study published by the Royal Society.
The researchers followed 27 apiaries with varying levels of infestation by Varroa destructor and analyzed nearly 1,000 pollinators and 350 flowers around the colonies, looking for the presence of DWV. According to the results, reducing the number of mites to levels below the threshold recommended for treatment allowed the viral load in the bees to be reduced by more than 100-fold.
The effect also extended to the surrounding environment. The prevalence of the virus on flowers dropped by more than 35%, while among wild pollinators, including bumblebees and hoverflies, the reduction ranged from 39% to 85%.
Varroa destructor is a parasitic mite specialized in honey bees and also constitutes an important vector of viruses. Among these is the deformed wing virus, which can cause the development of deformed wings in bees and compromise their behavior and foraging ability.
According to Phil Lester, professor of Ecology and Entomology at Victoria University of Wellington, cited by the Science Media Centre, the study led by Kaitlin Deutsch demonstrates that effective management of Varroa can influence not only the health and infection levels of honey bees but also those of other nearby pollinating insects.
The researchers found significantly lower levels of DWV in bumblebees and hoverflies near apiaries where Varroa infestations were kept under control. Flowers appear to play a role in transmission, since the viruses can be deposited and subsequently collected by different pollinators visiting the same flowers.
The flowers nearest to the hives and those located near apiaries with less effective mite control showed a higher likelihood of carrying the virus.
The work also draws attention to the presence of viruses associated with honey bees in a diversity of other insects. Studies conducted in New Zealand identified the DWV and other bee viruses in bumblebees, spiders, weevils and wasps, as well as invasive Argentine ants living near apiaries.
For Phil Lester, these results suggest that the viruses associated with honey bees are disseminated across New Zealand ecosystems and may infect a considerable diversity of insects. The researcher notes, however, that little is known about the long-term consequences of these infections and about their potential contribution to the decline of insect populations observed in various regions around the world.
The study is presented by the Royal Society as the first to demonstrate that the management of honey bee colonies can reduce the prevalence of pathogenic agents in the broader pollinator community.
