Euro-moth devastates conker trees

by Adam Blenford

They have marched relentlessly across continental Europe, leaving devastation in their wake.

Legions of tiny moths smaller than a human fingernail have declared war on the horse chestnut tree - and the invading army has now arrived in Britain.

It has caused nothing less than panic in the ranks of conservationists and could spell an end to thousands of the trees producing their familiar crop of conkers each autumn.

The marauding insect is the horse chestnut leaf miner, Latin name Cameraria ohridella, whose larvae eat thousands of the leaves in the space of only a few weeks.

It has already attacked the whiteflowering trees in Croatia, the Czech Republic, Greece, Hungary, Poland, Italy, Austria and France. Serious outbreaks were detected in Brussels and in the beer gardens of Munich.

In an effort to raise awareness of the damage the five millimetre-long pest could cause to Britain's 432,000 horse chestnut trees, the Forestry Commission has issued an Exotic Pest Alert to tree officers in every London borough.

But as it stands, the commission is at a loss over how to tackle the problem directly.

Pest control officers are reluctant to use insecticides in urban areas for fear of polluting the water supply and little is known about whether wasps which eat the moth's larvae in foreign countries can be introduced in Britain.

Ron Melville, chief conservator for the Forestry Commission in London, where the moth has been discovered, said the only active control was regularly to brush away fallen leaves - in summer and winter - in an effort to clear any remaining larvae.

"Hopefully then by the time it comes around to the hatching season again, there will be far fewer of them in the area," said Mr Melville. But he added: "I'm afraid that once you've got it, there is no real cure."

While the insect does not actually kill the trees, experts fear that left unchecked, the leaf miner could spread across Britain, turning leaves an autumnal shade of brown before forcing them to shed their foliage months earlier than usual. Traditional autumn pursuits could also suffer as nature's lifecycle is disturbed: conkers, the horse chestnut's famous hard-shelled fruit, can have their growth stopped or stunted by the leaf miner. In Wimbledon, the tree on which the moth was discovered has not grown any conkers this summer.

Mr Melville said: "The first eggs hatch in April or May, and from then on the moths can reproduce every two or three weeks, meaning that several generations can appear in a very short space of time. Once the moth and larvae take root in the tree, they can reproduce and spread very quickly. Plant hygiene is very important."

The discovery of the moth is so significant that Elliot Morley MP, the minister responsible for forestry, has written to Marian Comfort, a 79-year-old woman from Wimbledon, thanking her for spotting the insects in her garden.

Mr Morley wrote: "As a result of Mrs Comfort's swift actions, the Forestry Commission has been able to carry out a survey in the Wimbledon area to assess the scale of the infestation. It is always important to detect new invasions as early as possible so there is no doubt Mrs Comfort's interventions have been very helpful."

It was Mrs Comfort's decision to wrap a suspect leaf in foil and send it to the Royal Horticultural Society which prompted concerns among British gardeners.

Today, Mrs Comfort said: "When I saw the leaf, I thought the only way to find out what it was would be to send it off. Now I realise they are taking it very seriously indeed. In our garden, it looks like autumn came early."

© Associated Newspapers Ltd.

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