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Large-scale study shows reduced losses of European bees

New data from Europe shows that the overall mortality rate of honeybee colonies in the 2013-14 winter averaged 9%, much lower than in recent years.

August 11, 2014

4 Min Read
Large-scale study shows reduced losses of European bees

European bees are much healthier than many recent media publications appear to suggest, according to new field data from nearly 400,000 bee colonies from 21 countries in Europe and the Mediterranean that show that overwintering losses of honeybee colonies — an important indicator of general bee health — were at their lowest level in years in 2013-14, according to an announcement from Bayer CropScience.

"It is great to see that our bees have come out of the 2013-14 winter in the best shape for many years," said Dr. Christian Maus, 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."

The non-profit honeybee research association COLOSS (prevention of honeybee 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 2013-14 winter was, on average, 9% — losses below 10% are considered to be normal. This compares with loss rates of up to 37% that were recorded from individual countries in previous years.

Mite infestations

In winter, honeybees 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 honeybee 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 contributions of many factors which are correlated to colony losses seem to be very dependent on weather conditions," explained Dr. Romee van der Zee, COLOSS Working Group coordinator from the Dutch Centre for Bee Research. "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."


Restrictions on neonicotinoids came into force in Europe in December 2013 as a result of the European Commission's concerns that this group of crop protection products, which is used to control pests that damage field crops such as corn and oilseed rapeseed, might pose a risk to bees.

However, as many scientific studies, field monitoring data and risk assessments have shown, neonicotinoids do not cause harm to bee colonies under real-life field conditions when they are used responsibly and properly, according to label instructions, an announcement from Bayer said.

"It seems that everyone is looking for just one culprit for reduced bee health and colony losses, but you can't point the finger of blame at a single factor. Bees are facing multiple challenges around pests and pathogens, loss of foraging habitat and poor farming and beekeeping practices. Pollination matters to agriculture, hence safeguarding the health of bees is a shared responsibility of all the partners involved: farmers, beekeepers and industry," said Annette Schurmann, head of the Bayer Bee Care Center.

This is underscored by a landmark study published in May 2014 in the Proceedings of the Royal Society. A group of international scientists led by professors Charles Godfray and Angela McLean at the University of Oxford, analyzed the natural science evidence base relevant to neonicotinoid insecticides and insect pollinators. They concluded that "there is poor geographical correlation between neonicotinoid use and honeybee decline."

This is supported by findings outside Europe. A parliamentary report on bee health published by the Primary Production Committee in New Zealand in July 2014 confirms, "There is currently no evidence of the (colony collapse) disorder in New Zealand, although these pesticides (neonicotinoids) are commonly used here as a seed dressing and as foliar sprays. We heard that when anecdotal evidence of losses is investigated, the causes seem to be mainly Varroa or starvation rather than pesticides." The report notes that honey production and exports are rising.

The regulatory authorities in Australia also investigated the potential effect of neonicotinoid seed treatments on bee health. Their report "Neonicotinoids and the health of honey bees in Australia," published in March 2014 confirms that the introduction of neonicotinoids in Australia has brought a number of benefits such as healthy crops and more productivity, noting also that they are considerably more favorable for humans (and other mammals) than the older products they have replaced.

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