A new report on the health of honey bees in Canada says 58 per cent of the colonies in Ontario did not survive the winter, a figure that exceeds the 15-per-cent mortality rate seen as acceptable.
Among the possible causes cited for the colony failures are starvation during a long winter, weak queens, viruses and poisoning from pesticides, said the Canadian Association of Professional Apiculturists (CAPA), which compiled the survey.
The report comes as the Ontario government moves toward a system of restricting or licensing the usage of neonicotinoid pesticides, a widely used class of chemical linked to the losses of bees and other pollinators that are vital to the food supply.
Neonicotinoids are used on all grain corn, canola and some soybean to protect the crops against insects. It is also used by vegetable farmers and growers of ornamental flowers.
The pesticide is systemic, which means it is present throughout the plants, including the nectar and pollen eaten by honey bees and other insect pollinators that are responsible for a third of the food we eat.
Neonicotinoids are temporarily banned in Europe but widely used in North America.
Twenty nine scientists recently reviewed more than 800 scientific studies issued over the past five years and found neonictinoids are "a key factor in the decline of bees." Health Canada's Pest Management Regulatory Agency in September blamed bee deaths in Ontario and Quebec on planting corn treated with neonicotinoids. At Health Canada's direction, seed companies and growers took steps this year to reduce the amount of pesticide-laced dust generated by seeding machines.
But a recent study coauthored by University of Guelph professor Nigel Raine found bumble bees' foraging abilities were impaired by the consumption of neonicotinoids, and that chronic exposure to pesticides is a threat to colony survival.
According to the CAPA report, the Canadian average of overwintering bee losses was 25 per cent, a number that falls to 19 per cent when Ontario is excluded.
"This level of winter loss is considered a high winter loss for most Canadian beekeepers...." said the report. "Clearly the impacts of pest, pathogen and environmental factors continue to be a challenge though the year to beekeepers across Canada."
In 2012/13, wintering losses were 28.6 per cent; 15% in 2011/12; 29% in 2010/11, according to CAPA.
For 2013/14, New Brunswick had the second highest percentage of honey bee losses at 26 per cent. Alberta, which has the largest number of colonies, lost 18.5 per cent of its honey bee colonies.
Here are the 2013/14 overwintering bee colony losses by province:
New Brunswick 26%
Nova Scotia 23%