While some beekeepers reported losses of less than 25 percent, others experienced 75 percent mortality
DRESDEN, Ont. — Over-wintering colony losses are down in Ontario and the United States, but concern for honeybee health continues.
A recent U.S. Department of Agriculture survey found that the yearly loss from April 2014 to April 2015 rose to an unsustainable 42 percent and last year, summer colony losses of 27.4 percent were higher than winter losses for the first time.
“If beekeepers are going to meet the growing demand for pollination services, researchers need to find better answers to the host of stresses that lead to both winter and summer colony losses,” said Jeff Petis, a senior entomologist with the USDA’s Agricultural Research Service.
A beekeeper survey in Ontario puts over-winter losses at 30 percent, which is down from last year’s staggering 58 percent loss.
However, Lorna Irwin of the Ontario Beekeepers Association said the 30 percent figure is an average, and outcomes for individual beekeepers varied widely.
“It’s all over the map,” Irwin said.
“Some beekeepers had devastating losses and some fared quite well.”
Forty-five percent of beekeepers reported losses of less than 25 percent and 22 percent reported losses of more than 75 percent.
The top three suspected causes were colonies being too small, normal winter losses and pesticides. Of less concern to those surveyed were varroa mites, queen problems and insufficient food stores.
Seventy percent of respondents said “some” or “most” of their colonies were located within three kilometres of corn or soybean fields.
Factors other than varroa mites were said to be at play in both Ontario and the U.S,. given the aggressive action that most commercial beekeepers take to control the parasitic insect.
A report released a few weeks ago by Paul Kozak, Ontario’s provincial apiarist, refers to multiple “in-season” mortality reports from Ontario beekeepers for last year. These were characterized by the mass disappearance of worker bees, dead and dying bees at the colony entrances, loss of queen bees and the failure of colonies to thrive.
Fifty-two Ontario beekeepers reported in-season mortality incidents at 322 bee yards to the federal Pest Management Regulatory Agency, Kozak said. The incidents continue to be investigated.
Reported incidents during the planting season were lower last year than in 2013. However, mortality reports came later in the season.
“Overall, it is difficult to make conclusions based on a single field season, and it is important to track the issue over several years to understand the impact of weather, the routes of neonicotinoid exposure and the factors that influence bee health,” Kozak said.
He said Ontario beekeepers are also reporting high levels of queen loss and supersedure, which is the replacement of queens by the colony. Queen concerns were especially worrying in southern Ontario.
Challenges facing beekeepers are viewed as a threat to the industry’s ability to deliver pollination services.
The demand for such services is growing in Ontario, and beekeepers operated 112,000 colonies by the end of last year, thanks to rebuilding efforts.
As well, 30,800 colonies were sent out of the province last year.
“Since 2010, the number of Ontario colonies used for pollination in other provinces has … more than doubled,” Kozak said.
Up to 100,000 additional colonies may be needed in another 10 years because of the growing demand for blueberry pollination, he added.
Neonicotinoid insecticides have been cited as a major concern for beekeepers and other pollinators, but according to an article published recently in the Ecologist, it’s not the only concern connected to modern agricultural practices.
“Those of us who study bees are agreed that bees face many problems, of which neonicotinoids are just one,” said Dave Goulson, a biological science professor at the University of Sussex in the United Kingdom.
“There are few flowers, new bee diseases and parasites have invaded from abroad, and they are exposed to cocktails of many different pesticides throughout their lives.”
Goulson also cited a large one-year field study from Sweden that was recently published in Nature.
It found that honeybees were not significantly affected by canola grown with a neonicotinoid seed treatment containing clothianidin, but bumblebees fared poorly and solitary bees failed to reproduce next to treated fields.
“New work suggests that bees may be the canary in the coal mine, and that the environmental impacts of neonicotinoids go far beyond bees,” Goulson said.
“The pesticides accumulate and persist in soils for many years, routinely turn up in fresh water systems and are also found in wild plants growing in field margins.”