Warning: Oak processionary moth dangerous to the touch

Members of the public have been advised not to touch emerging caterpillars of the oak processionary moth for fear of irritation caused by toxin-containing hairs. The Forestry Commission has issued the following alert:

People in parts of London and Berkshire are being reminded by the Forestry Commission, Public Health England and local authorities not to touch caterpillars of the oak processionary moth, which are beginning to emerge in oak trees in these locations.

They are also advised to keep children, pets and livestock away from the caterpillars and their nests, and to report any sightings.

The affected areas are several boroughs in West and South-West London, Bromley and Croydon in South London, and Pangbourne in West Berkshire.

Caterpillars of the oak processionary moth (OPM), which was accidentally introduced to Britain from mainland Europe in 2006, are a tree pest and pose a threat to human and animal health.

They are a tree pest because they damage oak trees by feeding on the leaves, in some cases leaving the trees severely defoliated and vulnerable to other pests, diseases or drought.

They pose a risk to human and animal health because they have tiny, toxin-containing hairs which, on contact, can cause itchy skin rashes in people and animals. Eye and throat irritations have also been reported as symptoms.

The hairs can be blown on the wind, and left in the silken, web-like nests which the caterpillars build in oak trees. They pose the greatest risk from May to July, although nests should not be approached at any time.

The Forestry Commission is working with local authorities and land managers to tackle the outbreaks with a carefully controlled programme of tree spraying and nest removal.

Forestry Commission England director Ian Gambles said: ""We need, and welcome, reports of the caterpillars or their nests from the public or others, such as gardeners and tree surgeons, who are out and about in areas with oak trees.

"However, the public should not try to remove the caterpillars or nests themselves. This task needs to be carefully timed to be most effective, and is best done by specially trained and equipped operators."

For more information, visit the Forestry Commission website.