A PLAGUE of wasps could be on the way, a leading York expert has warned.

New research suggests the explosion in wasp numbers may be due to a change in farming methods.

Michael Archer, a former lecturer in animal behaviour and ecology at York St John College, has analysed data from wasps caught nationwide in 2002. He found that numbers of Common and German wasps had increased to levels not seen for more than 20 years.

Wasp numbers in Britain had been falling since 1980. Scientists believed intensive use of pesticides and hedgerow removal were responsible for the decline.

Wasp plagues, when up to 2,000 wasps at a time can pack in to each nest, were once common - but they have not been seen for decades.

Now Dr Archer, who has studied wasp behaviour in North Yorkshire for almost 40 years, believes government policy backing green farming methods could be behind a massive increase. The countryside stewardship scheme offers farmers incentives to set aside strips of arable farmland for diverse vegetation, which encourages insects.

Dr Archer, a trustee of the Yorkshire Naturalists' Union, said: "The recent increase in wasp numbers may be an indication that these schemes are working. From a biodiversity point of view this is a good thing, because it shows that our wildlife is recovering in the countryside."

His findings were backed by pest specialist Stephen Ellis, based at the crop research centre, ADAS High Mowthorpe, Malton.

Dr Ellis said: "I can see where Dr Archer is coming from. It would appear that what he is saying hangs together."

Ben Emmett, an insect specialist for Vitacress Salads, based in Leeds, said: "I would agree that in general the numbers of wasps are increasing, and a number of species have been doing so well that they have been moving northwards through the country.

"For example, some years ago hornets were only found in the south of England. Recently they have moved up into Yorkshire and even on into Scotland."

But Mr Emmett denied that the public had anything to fear from wasps. He said: "Nobody should worry about this. If you stay away from them, they will stay away from you."

Updated: 09:13 Saturday, August 07, 2004