The Forestry Commission has warned that a beetle, imported from China, could do "extensive damage" to British woodlands.

The Commission has issued an "exotic pest alert" after finding the Asian Longhorn Beetle in several places in the UK.

Dr Hugh Evans, a senior entymologist at the commission's Alice Holt Research Centre near Farnham in Surrey, says that if the beetle becomes dispersed throughout the country it could prove almost impossible to eradicate.

Dutch Elm disease changed the British landscape in the 1970s by killing large numbers of elm trees. The Asian Longhorn Beetle attacks not only the elm but a range of broadleaved trees.

In China, Japan and Korea it kills elms, horse chestnut, poplars, maples, alders, willows and a range of fruit trees. Dr Evans says there's nothing in the British climate to stop it from thriving here.

"It certainly is a real threat and we are taking it rather seriously" he says. "It's likely to do fairly well in the south of England particularly. Temperatures here are quite suitable for it to develop. It could kill not only forest trees, but street trees as well, so people may well see some of their prime specimens going from their back gardens."

The beetle is already destroying trees in the United States. Increasing trade with China is putting the trees of many countries at risk, and the insect has become well established in Chicago and New York. Precious urban trees are having to be felled to contain the beetle.

Damage to bark caused by larval feeding

Perhaps the greatest threat is to the maple sugar industry. Larry Myott, scientific adviser to the Vermont Maple Sugar Council says the maple is the Asian Longhorn's favourite tree.

"We're very vulnerable", says Mr Myott. "There are interstate highways everywhere and if there are these beetles floating around the country in packing cases they could drop off the truck at some point and these maple forests are all along the highway.

"It would be feasible that some could get established if we allow them into the country. Potentially down the road it could mean devastation to the industry."

The Asian Longhorn is large, more than an inch long, with a shiny black body marked with white patches. It has long striped antennae, after which it is named, sturdy legs, and substantial mandibles, with which it chews through tree bark to lay its eggs next to the wood.

The larvae, when they hatch, do most of the damage, boring large oval holes deep into the wood and eventually killing the tree.

Larvae bore deep into the wood

The best hope of stopping the beetle is to chop down affected trees. It may be possible in the future to use beetle diseases, or insecticide, but if the insects spread far enough that may not be practicable.

They lay up to 60 eggs at a time, in a variety of trees, travelling up to 200 metres from where they emerge from the wood as adults to do so. The life cycle can take two years to complete.

It is now illegal to import wood which shows signs of the beetle, and the public is being enlisted in the effort to keep it out of Britain. People are being asked to look out for the beetle itself when it emerges in the spring.