Dick Rogers and Klemens Krieger

A New Contribution to Sustainable Varroa Management

The Varroa destructor mite is a parasite which weakens honey bee colonies, by transmitting viruses which cause fatal diseases, making it particularly challenging for them to survive the colder months in the temperate climate zones in, for example, Europe and North America.

Poor preparation of colonies for winter and failure to control against pests like the Varroa mite provides for the perfect storm to harm honey bee colonies during these winter months. This may then lead to overwintering colony losses which is a good indication of the health of honey bee colonies in these regions.

“The mite is a key problem in Europe and North America where the Western honey bee prevails and has not built up a defense against the invasive pest from Asia and, as a result, losses have hit beekeepers the hardest”, says Dick Rogers, Principal Scientist and beekeeper at the Bayer Bee Care Center in North America. “Varroa populations in a beehive can double every three to four weeks during their breeding season, growing from 50 up to some 3,200 mites from the beginning of February to the end of August. The threat becomes more prevalent in late summer and fall in these temperate climate zones when breeding activity and number of bees in the hive starts to decline while the infestation with mites continues to increase.”

Dick Rogers
Dick Rogers
Dick Rogers, Principal Scientist and beekeeper for the Bayer Bee Care Program in North America

A recent report on preliminary honey bee colony loss data for 2016-17 in the USA, published by Bee Informed Partnership (BIP), in collaboration with the U.S. Department of Agriculture (USDA) and the Apiary Inspectors of America (AIA), indicates that US overwintering colony losses this last year, estimated at around 21 percent, represent an improvement on the previous year. “This latest report may be seen as evidence that beekeepers are doing a better job of managing the many factors that can lead to successful wintering and this brings a ray of hope to everyone who cares about bee health in the USA. The losses are still very high compared to the average EU overwintering losses, of around 9 – 17 percent seen in recent years” continues Rogers, “There is still much work to be done to improve the US situation so Bayer continues to be actively involved and committed to research and development of strategies to control the Varroa problem here in the USA and worldwide.”

Taking up the theme, Klemens Krieger, Global Head of Special Projects/Bee Health within Bayer Animal Health Development based in Germany, continues. “At Bayer, we’re working with bee experts on new approaches to control Varroa, which they also see as a major pest, as this will improve overall honey bee health. The search for new varroacides with a different mode of action to replace those long-standing older, currently registered chemistries is not easy. Even today, after 30 years of intense research effort, only four synthetic active ingredients are approved for Varroa control, two of which were developed by Bayer. If beekeepers don’t rotate these types of synthetic products selection of resistant Varroa mites can lead to treatment failure. This means they need a filled “toolbox” of different options they can use but the regulatory situation, which makes new product development long and costly, can be a major impediment to finding new varroacides,” he explains.

Klemens Krieger
Klemens Krieger
Klemens Krieger, Global Head of Special Projects/Bee Health within Bayer Animal Health Development
Varroa destructor mite
Varroa destructor mite
Varroa populations in a beehive can double every three to four weeks during their breeding season in temperate climate regions, growing from 50 up to some 3,200 mites from the beginning of February to the end of August.

All is not lost, however, and there is hopefully good news as a new technology has just been registered to go to market in many European countries to help combat the Varroa mite. The “Varroa Gate” is a plastic strip carrying the active substance installed as a gate at the beehive entrance so that all bees have to crawl through one of the holes in the strip to leave and enter the beehive. Bees pick up small doses, enough to control mites which are attached to them and inside the hive, but pose no risk to the bees themselves. This not only controls newly arrived mites, but also the mites hatched inside the hive. After installation in late summer, the new technology should last until the end of flight activity, between nine weeks and four months. This prevents re-infestion of the hive through drifting or robbing bees.

“Preliminary data from Germany suggest relatively high overwintering losses in many areas of the country may be seen in 2017 due mainly to the long, warm fall late in the 2016 season and humid weather in some regions hampering effective Varroa control treatments. It will be interesting to see how this compares to the fuller picture on honey bee colony overwintering losses across Europe when the latest COLOSS results are published soon”, Klemens says.

One thing is clear though, no matter what the losses reveal for beekeepers across Europe, they now have one new technology which they will soon be able to implement as part of their “Integrated Varroa Control Management” going forward.

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