Canadian honeybee colonies experienced a second straight year of higher than usual losses during the winter.

Pesticides designed to protect honeybees are losing their effectiveness, say agricultural researchers, leading to a second year in a row of heavy colony losses across Canada.

With the reduced effectiveness of pesticides, two varieties of parasitic mites, one called the varroa mite, the other called the tracheal mite, have again played havoc with bee colonies. Other factors, including a longer winter and wetter spring in some regions and a failure to control a newly introduced virus called Nosema ceranae have led to widespread colony losses.

British Columbia was the hardest hit this winter, said Rob Currie, a honeybee expert and associate professor of entomology at the University of Manitoba in Winnipeg. Beekeepers in Alberta, home to the largest honey bee population in the country, as well as New Brunswick and P.E.I. also reported colony losses of 30 per cent or higher.

"Every year it's getting more and more difficult," Currie told CBC News. "There's no question it's a challenge right now for colonies to survive."

In total, about 26 per cent of the over 600,000 colonies across the country were lost over the winter, according to a June 4 report from the Canadian Honey Council, the industry group representing both commercial and hobby beekeepers. Normal losses during wintering are usually around 15 per cent.

It's bad news not only for honey producers but also a host of farmers who rely on the bees to help pollinate their food crops. Around the world, honeybees pollinate apples, cucumbers, alfalfa, blueberries, almonds, squash, watermelons, cantaloupes and a huge variety of other fruits and vegetables — an important contribution to an industry worth tens of billions of dollars.

Alberta is particularly reliant on the insects for production of hybrid canola, while provinces like British Columbia and Ontario rely on them for berry pollination. In situations where the bees are unable to meet the pollination demands it can lead to less food production and higher prices for consumers. The Canadian Honey Council said the price of honey itself is at $1 per pound, or 20 per cent higher than a year ago.

The Council has asked federal Minister of Agriculture Gerry Ritz to provide $50 million in immediate relief and $10 million in research to assist the industry in recovery.

No Colony Collapse Disorder yet

The experience of Canadian beekeepers echoes that of those in the U.S., where 36.1 per cent of the nation's commercially managed hives have been lost since last year, according to a survey commissioned by the Apiary Inspectors of America and released in May.

Paul Laflamme, head of Alberta Agriculture and Food's pest management branch, said that while many U.S. losses have been blamed on a mysterious ailment called Colony Collapse Disorder, no cases of CCD have been confirmed in Canada.

Instead the two parasitic mites that started infesting bee colonies in the mid-1980s are seen as the primary reason for the failure of colonies across the country. The tracheal mite, believed to have entered the U.S. from Mexico, sucks blood from honeybees by burrowing into a bee's windpipe. The larger varroa mite lives on the outside of bees and destroys the insects' reproductive cycle.

Beekeepers have been using pesticides and other more labour intensive methods to deal with the mites, but now it appears the pesticides have lost their effectiveness, said LaFlamme.

"There are only two miticides registered in Canada to control these mites, and the mites have developed a resistance to both of them," said LaFlamme.

John Gibeau, the president of the British Columbia Honey Producers Association, said there are natural treatments for dealing with the mites that don't require pesticides, including the use of formic acid, thyme oil and a process called drone brood trapping, which isolates the most likely place for mite infestation from the rest of the hive.

But he said these measures are most effective when alternated with pesticide use, and Currie said natural methods and practices such as drone brood trapping require far more intensive management.

Mites are 'sophisticated' pest

Paul van Westendorp, the provincial apiculturist at the B.C. Ministry of Agriculture and Lands, said the problem with the varroa mites in particular is that they are vectors for a host of diseases and viruses, including the Kashmir Bee Virus, which was first diagnosed in Canada in 2004 in the Fraser Valley, where it had a devastating effect on the honeybee population.

"We're talking about the most virulent pest known to bees. It's a pretty sophisticated creature on its own and now its transmitting viruses," said van Westendorp. "To find a product that's virulent to mites but harmless to the bee is a tall order."

Beekeepers deal with colony losses by either importing colonies from countries like New Zealand or splitting their existing colonies. But many of the colonies still functioning are already very weak, say experts, putting a further strain on the industry.

This can often accelerate the exit from the industry of many commercial beekeepers, said van Westendorp, putting a further strain on those who are left to travel further afield to pollinate. In British Columbia that's already begun to happen, with 30,000 colonies from Alberta transported every year to the South Okanagan and Fraser Valleys to help pollinate blueberries and other fruits there.

The stress of transport is a growing concern for beekeepers, particularly since many of the U.S. colonies that were wiped out from CCD were migrant colonies, travelling across the country to pollinate different crops in different states.

But tracking CCD here is more difficult in Canada than in the U.S., since some of the key indicators of CCD occur during early-season pollination, a time when much of Canada is still under a foot of snow, said van Westendorp.

Van Westendorp said the cause of colony deaths could be mites, CCD, viruses, weather, stress or beekeeper error, or a combination of any number of these factors. He said the only protection is constant vigilance.

"I'd love to have the recipe, but the best thing beekeepers can do is be knowledgeable, particularly in the field of mite management. This isn't something where you can take a tablet and the problem is solved."