Bees: Overwintering losses are significant concern
Wednesday, May 14, 2014, 11:19 -
Pollinators are an extremely valuable resource. At least one third of the human food supply from crops and plants depends on insect pollination, most of which is done by bees. There are over 600,000 colonies of honeybees in Canada and they contribute as much as $2 billion annually in food production, in this country alone.
History has taught us, however that the Canadian winter is generally not friendly to bees and after the winter we have just experienced, that trend can be expected to continue. Colder than normal temperatures across the country will mean beekeepers are likely to find high levels of dead bees in their apiaries this spring.
According to Statistics Canada, bee populations in Canada are higher than they have ever been. There has been an increase of approximately 40 percent in the number of bee colonies in Canada since the 1950s. However, the health of colonies has been a concern for a number of years.
Extensive colony losses are not unusual and have occurred over many centuries and parts of the globe. For example, in 1906, beekeepers on the Isle of Wight noticed that many of their honeybee colonies were dying. Years later, scientists determined that a combination of factors caused the “Isle of Wight Disease”. The bees were infected by chronic bee paralysis virus (unknown at the time) and a tracheal mite. In addition, they lacked sufficient food since bad weather inhibited foraging and too few flowers were available. The disease spread quickly, nearly wiping out Great Britain’s entire honeybee population.
Overwintering losses of honey bee colonies fluctuate from year to year, and do not occur uniformly across the country. Hives may die off naturally during the winter due to a variety of factors, such as starvation or stress caused by diseases. Average winter mortality of 15 percent is considered normal. However, this number can and does fluctuate significantly. For example, bee experts have pointed to losses in Ontario as well as other parts of Canada that have fluctuated from a high of more than 40% in 2011 to a low of about 12% in 2012, both of which were driven by abnormal weather patterns (i.e. long, cold winter-like conditions in 2011 versus the warm weather, early spring experienced in 2012).
Canadian and international bee researchers agree that the overwintering success of bee hives is impacted by a variety of factors, including stress caused by parasitic mites, viruses, disease and starvation due to weather and/or management practices. While overwintering losses do naturally occur, the scientific community is looking at ways to preserve and enhance the strength of bee colonies throughout the winter in an effort to reduce these losses.