Scientists are fighting to stop a poisonous caterpillar from threatening to kill off thousands of oak trees. Source: Mail Online
Efforts to cull the oak processionary moth, which can be toxic to humans, have failed, leaving experts mounting a rearguard action to stop it spreading.
Larvae have been destroying trees around London for the past month after the insect came into the country on infested trees imported from Europe.
Its caterpillars strip leaves from the trees they occupy with their nests, often in such large numbers that the oak is fatally weakened.
Trees are left covered in toxic hairs, which can burn the eyes and skin of anyone touching them. In severe cases, victims can suffer anaphylactic shock.
Scientists admitted that they are unlikely to be able to eradicate the moth. Instead, the best they can hope for is to ‘slow its spread’ by containing it in the areas already infected.
Larvae have hatched across the capital in the last few weeks from Richmond Common and Kew in the west to Croydon and Bromley in the south.
But, in a worrying indicator that the infestation is more widespread, an outbreak has also been found in Pangbourne, Berkshire.
Oaks are the moth’s favoured habitat but it can also eat hazel, hornbeam, sweet chestnut, birch and beech trees.
Tony Kirkham, head of the Kew Gardens arboretum, said gardeners have previously been poisoned by the caterpillars.
Staff are on standby to spray trees with pesticides, which has kept the outbreak there under control in the last five years.
“We have cleared thousands of nests from trees,” said Kirkham. “We hope it is under control in Kew but it looks like it is established in the wider area of London.
“In Belgium, caterpillar infestation became so bad that the army was sent in to incinerate nests.
“The moth earned its name because of the nose-to-tail ‘processions’ the caterpillars form when stripping foliage.
“Their threat to humans comes from 700,000 toxic hairs found on each caterpillar, which contain the irritant chemical thaumetopoein.
“Even people walking near a nest can be affected as the hairs become detached and are carried by wind. There’s every chance it could spread. It’s a worrying pest and it’s a new pest.”
It is thought the moth came to south-west London in 2006 on an infested oak from Italy.
Larvae have been hatching in the area since then, despite eradication efforts by the Forestry Commission. But its entomologists have said they are now focused on slowing its spread.
The outbreaks in Bromley and Pangbourne are believed to have been caused by other infested trees from the Continent. The commission is hopeful these areas can be cleared.
It is thought the growing trade in shrubs and trees has enabled the moth to spread across Europe in the past decade.
Since 2009, Richmond Council has spent £200,000 trying to eradicate the pests.
