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Study sheds light on bee colony losses

Study suggests that the varroa mite, which resembles a tiny crab no bigger than a sesame seed, is the main culprit in bee colony losses in Ontario.

 

The varroa mite attaches to the bee body and weakens it by sucking body fluids.

Over the last three years, winter mortality of honey bee colonies has been higher than normal in several parts of the world.  A recent study led by Dr. Ernesto Guzman-Novoa, at the University of Guelph suggests that fall infestations by a tiny parasite were the leading cause of colony mortality in Ontario. 

The research team looked into the effect of five factors on bee populations: low food reserves; low bee population prior to overwintering; nosema disease; infestations of tracheal mites; and infestations of varroa mites.  They collected samples from a total of 408 randomly selected commercial honey bee colonies in six different regions of southern Ontario. 

The varroa mite, or Varroa destructor, is an external parasite about the size of a sesame seed, which attaches to the bee and weakens it by sucking body fluids. In comparison, this parasite on a human body would be the size of a dinner plate!

The varroa mite was first reported in Canada in 1989. Although infestations are not new in honey bee colonies, the mites have developed resistance to the most common treatments. This explains why they have become more of a threat to honey bees over the recent years.  

In addition to varroa mite infestations, the study showed that fall bee populations and food reserves also had a significant effect on colony mortality.  

The results of the study, combined with the recently published 2010 Recommendations for Honey Bee Disease and Mite Control, will help Ontario beekeepers make management decisions this year and beyond.  The recommendations are prepared each year by the Ontario Ministry of Agriculture, Food and Rural Affairs, in cooperation with the University of Guelph and the Ontario Beekeepers Association.

Contact: Dr. Ernesto Guzman-Novoa
University of Guelph

Watch a video of Dr. Guzman’s presentation.

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