Mites might be the biggest threat to bee health

October 11, 2013

From: Farmers Weekly (U.K.)

Many scientists believe the varroa mite is more important than pesticides in hitting bee numbers, so one big agrichemical group is looking at ways to control the pest. David Jones reports.

Bayer is close to launching a product to improve bee health as the well-being of these pollinators has taken centre stage with a ban on neonicotinoid pesticides.

The two-year curb on some of these chemicals due to a possible link with bee health has left many oilseed rape growers in a quandary on how to control autumn pests.

Despite the ban, many scientists believe the varroa mite is the biggest single threat to bee health as its carries a number of viruses and diseases which hit bees.

In response, the German agrichemical giant is hoping to launch a remedy within three years which will kill mites and restore bees to a healthier state.

This so-called varroa gate is a device which forces bees entering a hive to pass through a narrow aperture which will brush insecticides across their bodies.

“This is proving very promising in controlling mites and producing healthier bees,” Annette Schurmann, head of the Bayer Bee Care Centre says.

Trials over the past two years have been positive and the first full-scale field trials are now being undertaken in Germany and France looking at different insecticides and dose rates.

“This product could be available in 2016 or 2017, as the early signs are that the bees look healthier,” Ms Schurmann adds.

Her goal is to devise a system whereby different insecticides could be used in rotation over a number of years to prevent resistance building up.

Bee decline

Bee numbers have been declining in Europe for a number of years and the European Commission earlier this year moved to ban three neonicotinoid pesticides.

These are largely used in Britain as seed treatment in oilseed rape, and Bayer CropScience and Syngenta, which make the two main products Modesto and Cruiser, are challenging the ban.

These products have been in use for more than two decades and Bayer believes the varroa mite – rather than these pesticides – is the main reason for the decline in bee numbers.

It points to the experience in Australia and France which has highlighted the importance of the varroa mite, rather than these pesticides, in affecting bee health.

“Australia is the only place on earth without varroa, and Australia has the healthiest bees in the world,” Ms Schurmann says.

This is despite the wide-spread use of neonicotinoids used in oilseed rape in the southern continent.

In addition, Bayer adds that despite some neonicotinoid products being restricted in France over the last 10 years, there has been no significant improvement in bee health.

The varroa mite first appeared in Europe in the late 1970s, arriving from Asia, and over the last 25 years Bayer, utilising its interests in animal health and crop protection, has been looking at bee health.

Neonicotinoid ban

The European Union is banning the use of three neonicotinoid pesticides for two years, starting on 1 December 2013.

These include imidacloprid, clothianidin and thiamethoxam as used in seed treatment products such as Bayer CropScience’s Chinook and Modesto, and Syngenta’s Cruiser.

As nearly 10% of the world’s food production – largely edible oilseeds, fruit and vegetables – need to be pollinated by bees, Bayer saw that declines in bee numbers would hit its grower customers.

To control mites, Bayer introduced Bayvarol more than 10 years ago in the form of strips impregnated with a pyrethroid pesticide to hang within bee hives.

Despite some success, the group has moved to look at a more precise method of applying pesticides to bees with minimum disruption within the bee hive.

The bee centre at Bayer CropScience’s Monheim headquarters just south of Dusseldorf has been working on improving bee health for a number of years.

Manuel Tritschler, Bayer’s bee health expert, says varroa mite levels have been lower this year due to the late spring and the delay in bee breeding which restricted the buildup of mites.

This season he is using pesticide strips in the hives at the group’s bee centre, but is upbeat about the prospect for the varroa gate.

“The trial has been positive and it is clear that controlling mites produces healthier bees,” he says.

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