Fungus fights deadly bee mites in a two-pronged attack

Oct 22, 2012
A Varroa mite on a honey bee pupa. Credit: Gilles San Martin

(Phys.org)—A fungus normally used to control insect pests may help honey bees protect themselves from a destructive mite by both infecting the mites and preventing suppression of the bee immune system, says a team of bee researchers at the University of Guelph.

The is a devastating bee pathogen that, if left untreated, can kill an entire . Beekeepers typically treat their colonies with miticides to control the mites, but resistance to these chemicals has become widespread. The Varroa mite is believed to be a leading factor in the high winter mortality experienced in Canadian in recent years.

"Beekeepers have an urgent need for effective, bee-friendly Varroa treatments. Naturally-occurring entomopathogenic fungi could be an effective, biologically-based control method. They are non-toxic to humans and can be mass-cultured," explains Mollah Md. Hamiduzzaman, a post-doctoral researcher in the School of Environmental Sciences and lead author of the study.

Hamiduzzaman and colleagues looked at in larvae exposed to regular mites and mites inoculated with fungus. Infection with Varroa typically leads to lower expression of genes involved in the bee immune response, leaving bees less able to fend off the parasite. When mites were first inoculated with the fungus, however, expression of three important immunity genes jumped 2-3 fold over normal levels. "The results suggest that the fungi could reduce damage from Varroa mites by both infecting the parasites, and preventing the mites from suppressing the bee's natural immune response," says Hamiduzzaman.

Because the fungi are natural insect pathogens, however, the honey bees can also be vulnerable to infection from the fungus. According to Ernesto Guzman, an entomologist and collaborator on the study, "the trick is to find a fungus that kills Varroa at doses that are relatively harmless to the bees". The team looked at several strains of fungus and identified one strain of Metarhizium anisopliae that causes high mite mortality (over 90%) and relatively low bee mortality (24%). Guzman says it may be possible to find other strains that are just as effective against mites but less harmful to honey bees.

Another interesting possibility, adds Guzman, is to isolate the factors that trigger the enhanced bee from the fungus. "These compounds could potentially then be applied to hives to trigger a natural defense against Varroa infections."

Graduate student Alice Sinia and pathologist Paul Goodwin also collaborated on the study. The results have been published in the most recent issue of the Journal of Invertebrate Pathology.

Explore further: Meteorite that doomed dinosaurs remade forests

More information: Hamiduzzaman, M.M., A. Sinia, E. Guzman-Novoa and P. Goodwin. 2012. Entomopathogenic fungi as potential biocontrol agents of ecto-parasitic mite, Varroa destructor, and their effect on the immune response of honey bees (Apis mellifera L.). Journal of Invertebrate Pathology 111(3) 237-243. (published online: dx.doi.org/10.1016/j.jip.2012.09.001 )

add to favorites email to friend print save as pdf

Related Stories

Fungus Foot Baths Could Save Bees

Jul 28, 2008

One of the biggest world wide threats to honey bees, the varroa mite, could soon be about to meet its nemesis. Researchers at the University of Warwick are examining naturally occurring fungi that kill the varroa mite. They ...

Bees Throw Out Mites

Sep 11, 2009

Honey bees are now fighting back aggressively against Varroa mites, thanks to Agricultural Research Service (ARS) efforts to develop bees with a genetic trait that allows them to more easily find the mites ...

'Swindon Honeybee' could save Britain's bees

Aug 27, 2010

(PhysOrg.com) -- Honey bee numbers have been declining almost everywhere due to a pesticide-resistant mite called Varroa. Now a beekeeper in Britain claims to have discovered a strain of bee that destroys ...

Bee scientists force killer mites to self destruct

Dec 22, 2010

The blood-sucking Varroa is the biggest killer of honey bees world-wide, having developed resistance to beekeepers’ medication over the past decade. It particularly thrives in cold winters when colonies ...

Recommended for you

Slimy fish and the origins of brain development

15 minutes ago

Lamprey—slimy, eel-like parasitic fish with tooth-riddled, jawless sucking mouths—are rather disgusting to look at, but thanks to their important position on the vertebrate family tree, they can offer ...

Global importance of pollinators underestimated

18 minutes ago

(Phys.org) —Declines in populations of pollinators, such as bees and wasps, may be a key threat to nutrition in some of the most poorly fed parts of the globe, according to new research.

Meteorite that doomed dinosaurs remade forests

19 hours ago

The meteorite impact that spelled doom for the dinosaurs 66 million years ago decimated the evergreens among the flowering plants to a much greater extent than their deciduous peers, according to a study ...

User comments : 0