European bees are at their best health level in years
European bees are much healthier than many recent media publications appear to suggest. New field data from nearly 400,000 bee colonies from 21 countries in Europe and the Mediterranean show that overwintering losses of honey bee colonies – an important indicator of general bee health – were at their lowest level in years in 2013/2014.
“It is great to see that our bees have come out of the 2013/2014 winter in the best shape for many years,” said Christian Maus, Ph.D., global pollinator safety manager at Bayer CropScience. “These results are also very telling since the data relate to a season during which neonicotinoid-based crop protection products were still in common use throughout Europe. This offers further evidence that these important components in the toolbox of farmers do not impact the survival of honeybee colonies during overwintering under real-life field conditions,” Maus adds.
The non-profit honey bee research association COLOSS (prevention of honey bee COlony LOSSes), which comprises more than 360 scientific professionals from 60 countries, has published new data showing that the overall mortality rate of bee colonies in the 2013/2014 winter was on average 9 percent – losses below 10 percent are considered to be normal. This compares with loss rates of up to 37 percent that were recorded from individual countries in previous years.
Mite infestations impact overwintering
In winter, honey bees are generally not active outside the hive; they are very busy inside taking steps to ensure the colony's survival. They continue to access stored food – honey and pollen – and generate heat within the hive to protect the colony. If adequate provisions have not been made during the summer and fall, e.g. by the beekeeper, then a colony may not survive the winter season because of starvation.
Another major factor affecting honey bee colonies in the winter is Varroa mite infestation, often linked with secondary infestations by viruses. Adult winter bees that were infested with Varroa as immature bees within the brood cells do not fully develop the physiological characteristics of a long-lived winter bee. This makes them less likely to withstand the grueling environmental stressors associated with winter conditions and survive until the spring.
The coordinator of the COLOSS Working Group, Romée van der Zee, Ph.D., from the Dutch Centre for Bee Research, explains, “The contributions of many factors which are correlated to colony losses seem to be very dependent on weather conditions. Colonies built their brood nests late because of the relatively cold spring in 2013. This may have decreased the number of reproductive cycles of the parasitic Varroa mite, producing fewer mites. Good weather in the summer then provided excellent foraging opportunities.”
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