Toxic caterpillar nests should be avoided by people and their pets as the pests enter their peak nesting season this month, authorities have warned.

Residents in some areas across Surrey and southwest London are being reminded not to touch the nests of the oak processionary caterpillar that makes its home in oak trees, especially during June.

People are also being advised to protect animals from contact with the nests and to report sightings to the Forestry Commission or their local council.

The warning has been issued because the nests are filled with the caterpillars’ hairs containing an irritating substance that can cause unpleasant skin rashes and, occasionally, eye and throat irritations in people and animals.

The caterpillar is the larval stage of the moth and is a tree pest that, in large numbers, can strip oak trees bare of leaves, leaving them weakened and vulnerable to other threats.

In June it builds distinctive white, silken, webbing nests and trails on the trunks and branches of oaks.

Councillor Tim Godfrey, Croydon Council's cabinet member for culture, leisure and sport, said: “It’s important that people pay heed and don’t touch – and keep their children and pets away from – these nests.

“Council teams have been out with Forestry Commission officers removing nests as they’re reported, but people should remain vigilant, particularly around Shirley and Ashburton, where the nests have been seen in the past.

“Anybody who sees nests or caterpillars should report them to us, on 020 8726 6200, or the Forestry Commission, so that they can be dealt with properly.”

Ian Gambles, of the Forestry Commission, encouraged people to help tackle the pest by reporting sightings of the nests and caterpillars, but not to touch or approach them.

He said: “We advise people against trying to remove the nests themselves, even if they own the oak tree.

"To be as effective and safe as possible, this job needs to be timed just right and done by people with the right training and equipment, and the nests must be disposed of properly.

"The Forestry Commission is working with local authorities and tree owners to eradicate or contain the pest under a Defra-funded programme.”

People are advised to see a pharmacist for relief from milder skin or eye irritations following possible OPM contact, or consult a GP or NHS111 for more-serious reactions. Contact a vet if pets are affected.

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