Mites called biggest honeybee enemy

The varroa mite is emerging as the leading culprit in the death of Ontario honeybees, researchers say.

Scientists at the University of Guelph monitored colonies in six southern Ontario counties from fall 2007 to summer 2008, counting the bees, weighing the colonies to gauge their food reserves and testing the bees for various mites and the Nosema fungus.

Varroa mites were associated with more than 85 per cent of colony deaths, according to the findings published online in the international journal Apidologie.

Other factors contributing to the death of bees included too sparse beehive populations in the fall and insufficient food reserves for the winter, researchers found.

There's been suspicion that the varroa mite was a major culprit for the losses we've been experiencing," said Ontario Beekeepers' Association president Tim Greer.

"I believe that the Canadian beekeeping industry maybe underestimated the effects the varroa mite would have on beekeeping here in Canada, when we knew that it was inevitable that it would sooner or later arrive to our Canadian bees."

The industry does treat for the varroa mite, but with varying degrees of success, Greer said.

He saidthat the presence of the mite contributes to weakening the condition of the bees and making them susceptible to other diseases, pests and viruses.

Ontario beekeepers have experienced three years of higher-than-average losses in the 30 to almost 40 per cent range, he said.

The majority of the province's 2,200 beekeepers are hobbyists, Greer said.

Ontario has about 80,000 hives, each one containing approximately 30,000 to 80,000 bees.