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Public reminded not to touch Oak Processionary Moth caterpillars


Monday, 11 May, 2020

The first sighting of the Oak Processionary Moth (OPM) of the year has been confirmed in the Borough. Residents are being reminded to avoid all contact with this hazardous tree pest.

The caterpillars have black heads and bodies covered in long white hairs, which contain proteins that can cause itchy rashes, eye, and throat irritations. They can also occasionally cause breathing difficulties in people and pets, so should not be touched under any circumstances.

Oak Processionary Moths have been present in the UK since 2012 with infestations found in London and parts of the South East in recent years. They can be identified by their dome or teardrop-shaped nests, which range in size from a ping pong ball to as large as a rucksack. They are white when fresh, but soon become discoloured and brown.

The greatest risk period is May to July when the caterpillars emerge and feed before pupating into adult moths, but nests, even old ones, should not be touched at any time. The caterpillars feed on oak leaves, which can leave the trees vulnerable to other pests, diseases and drought.

Craig Harrison, the Forestry Commission’s South-East England Director, said: “Now more than ever people are appreciating the value of their local woods, parks and gardens for daily exercise and wellbeing. We want them to be safe places for everyone to enjoy, and the public can help us by reporting OPM nests and caterpillars to us.

“However, please don’t try to remove the nests yourself. To be as effective and safe as possible, this job needs to be done by people with the right training and equipment, and the nests must be disposed of properly.”

Cllr Kevin Davis, Woking Borough Council’s Portfolio Holder for the Environment, said: “Where the caterpillars or their nests are identified on public land, the Council follows Forestry Commission guidance to deal with the infestation. Meanwhile, we continue to urge residents not to touch the caterpillars if they believe they have found a nest and to make sure you look after your pets as they can also be affected.

“All sightings of caterpillars and nests on either public or private land need to be reported to the Forestry Commission, which has a programme in place to tackle the pest.”

What to look out for:

  • OPM moths, the adult form of the species, are undistinctive brown moths similar to other species, and are difficult to accurately identify. They are not a health hazard and do not need to be reported unlike their junior forms.
  • OPM caterpillars have a distinctive habit of moving about in late spring and early summer in nose-to-tail processions, from which they derive their name. They live and feed almost exclusively on oak trees and can sometimes be seen processing across the ground between oak trees. They have very long, white hairs which contrast markedly with the much shorter, almost undetectable irritating hairs; have a grey body and dark head. Older larvae have a central dark stripe with paler lines down each side.

To report a sighting of OPM visit, email  or call 0300 067 4442. You will need to give a precise location as to where the infestation was sighted and, if possible, provide a photo.

OPM nest are built in early summer on the trunks and branches of oak trees. They are made of distinctive, white, silken webbing and are accompanied by white, silken trails. These become discoloured after a short time and more difficult to see as a result. Several nests can occur on the same tree or branch, anywhere from ground level to high in the oak tree.