The Canadian Association of Professional Apiculturists survey found that 58 per cent of Ontario bees died during what was an especially long winter, while other provinces lost on average about 19 per cent of their swarm.
While the report fingers the weather as the main culprit for the bee deaths, hive-minders in Ontario and Quebec also cited acute and chronic pesticide damage or insufficient recovery from pesticide exposure last year as contributing factors.
Ontario Beekeepers' Association president Dan Davidson says bees' exposure in the hive to pollen contaminated by pesticides "almost guarantees they will not survive the winter."
The group is calling on the governing Liberals to fast track a plan looking at permits restricting the number of plant seeds treated with neonicotinoids, a widely used pesticide that some scientists and environmentalists say are killing bees and other insects.
The apiculturists association states Canada's overall winter mortality rate averaged 25 per cent, well above what it says beekeepers deem the "acceptable" loss limit of 15 per cent.
The Ontario bee group says nearly all corn seeds and about two-thirds of soy seeds sold in the province are pretreated with neonicotinoid coatings, though only a minority of the crops are at risk from pests the insecticide is meant to stop.
It did its own winter survey earlier this year and found more than a quarter of beekeepers lost 75 to 100 per cent of their colonies.
"Beekeepers cannot sustain these losses and many will have to leave the business if these losses continue," group vice-president Tibor Szabo said in a release Wednesday.
"The government of Ontario must immediately take the initiative to ensure this permit (system) is in place for the 2015 growing season if we are to have a sustainable industry as well as the pollinators we need for our fresh fruits and vegetables."
An international panel of 50 scientists working as the Task Force on Systemic Pesticides said last month the use of neonicotinoids and another popular insecticide called neonics should be phased out.
The panel said its study of 800 research papers provides conclusive evidence that the pesticides are causing the mass deaths of insects that are essential to the process of pollinating most crops.
A Health Canada report has suggested that seeds treated with neonicotinoids contributed to the majority of the bee deaths in Ontario and Quebec in 2012, likely due to exposure of the pesticide-laced dust during planting.
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