Whatever is behind the high losses in our bee yards, the Canadian bee experts tell us that it is not Colony Collapse Disorder, the disorder that has devastated the US pollination industry and honey producers.

So, what is to blame? It’s too soon to tell for sure… However, apiculturists suspect that unusual winter weather — we’ve all remarked on it — could be the main factor behind this year’s staggering losses of honeybees in Canada.

The numbers for New Brunswick are still coming in, as beekeepers get out into the yards and check their hives, but it looks very much as if our beekeepers have suffered colony losses in the order of 80% or more overall.

Interestingly, the lowest death rate (about 20-30%) occurred among those colonies that were wintered indoors. Beekeepers who wintered their bees outdoors — a method which has traditionally proven more successful in our region — had much higher losses.

This lends some weight to the suspicion that weather played a large part…

Dry weather conditions through Autumn 2006 meant that less nectar was available to the bees, and many colonies would have gone into winter with less than the usual amount of late-season honey they depend on for winter stores.

Meanwhile, relatively mild temperatures through into January may have caused the queen to continue laying eggs later into the season, thus extending the breeding period for Varroa mites as well. By the time the weather suddenly turned very cold, in mid-January, it would have been quite some time since the last Formic or Oxalic Acid treatment was applied. As a result, the Varroa would have had a good chance to rebuild their populations and could have been at very high levels going into the cold weather.

After the middle of January, the increasing length of days is a natural signal for bees to raise the temperature of the hive. Through most of the winter, they keep it at 21°C, but longer days are a signal to prepare for brood raising. The bees tighten up their cluster to raise the temperature to 35°C — and they’ll starve to death rather than leave the cluster.

In the warmer part of winter, the cluster would have been able to spread out to get stores. Once they went into a tight cluster, and the dangerously cold weather hit, they could have found themselves stranded in the middle of some empty frames — there could be plenty of stores in the hive, but just too far away for the bees to get to it.

Not surprisingly, a number of beekeepers have noted clear indications of starvation in dead-out colonies that were quite strong when put away for winter. Trying to maintain the hive temperature would have been even more difficult for weak hives, of course.

At the moment, the unusual weather conditions seem likely to be the major factor behind this winter’s extremely high losses (perhaps in combination with other stresses) — but Canada’s bee researchers and provincial apiarists are continuing to investigate, in consultation with their American counterparts.