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Consequences of a warm winter

Winter losses of honey bee colonies in 2014 differ significantly between countries.

Aug 31, 2015
Honey bee overwintering losses across Europe is quite heterogeneous

Honey bee overwintering losses across Europe is quite heterogeneous

The current report of the organization COLOSS (Prevention of honey bee COlony LOSSes) reveals how honey bee colonies in Europe, Egypt, Russia and the Ukraine survived the winter 2014/15. In total, it summarizes data from 31 different countries. Out of 469,249 managed honey bee colonies, 67,914 did not survive the winter. This translates as 17.4 percent which is roughly twice as high as in the previous year.

In contrast, there were significant differences between individual countries: Bee losses ranged from between five percent in Norway and more than 36 percent in Belgium. “The situation in Europe is quite heterogeneous”, says Peter Trodtfeld, apiarist and bee expert at the Bayer Bee Care Center in Germany. One important reason for the regional differences is the weather. Norway and other Scandinavian countries usually have a long wintertime and lower temperatures in spring. “When it’s cold, the bees’ breeding season starts later. That also has a big impact on the reproduction of the Varroa mite”, explains Trodtfeld. Bee colonies in cold regions were less infested with the parasite.

On the other hand, the warm winter in some countries increased the mites’ reproduction: Where the bees’ breeding season started sooner, the mites were also able to nest in the honeycomb cells and had more time to reproduce themselves. Bayer’s expert thinks that this is the main reason for the high bee mortality in some regions: “Compared to recent years, many beehives where highly infested earlier in the year. The scheduled Varroa treatment was then too late to save damaged colonies.”

In Germany 21 percent of the bee colonies did not survive the winter season – this was lower than had been initially predicted in spring, when experts expected about 30 percent of the colonies to perish. “It looks like we were lucky to get away fewer losses. Nevertheless, the winter losses are twice as high as last year”, says Trodtfeld about the results of the COLOSS study. “This shows that we still have to work on our overwintering strategy, to have more success in protecting our bees, next year.”

Preparations for winter 2015/16 have already begun and the work of beekeepers plays an important role: Particularly important is an effective anti-mite treatment with so-called varroacides. But also a good nutrition can help keep bees healthy and fit.

You can read the full results of the international COLOSS study here.

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