Oak processionary moth (OPM)

About the moth

The oak processionary moth (Thaumetopoea processionea) is a pest that was introduced into the UK upon imported Oak trees. It was first identified at a private development in the borough in 2006 and is now established in south and south west London and has now been confirmed within Buckinghamshire. 

Health risk

The caterpillars of this pest feed almost exclusively on oak trees and pose a risk to human and animal health. They emerge from minute egg plaques in April of each year, following hatching the larvae feed upon oak leaves, and go through several stages of growth which are known as instars.

As the caterpillar reaches its third growth stage it begins to develop urticating hairs. These hairs contain an irritating substance which can cause skin rashes, eye problems, sore throats and breathing difficulties for people who come into contact with them. Animals are also at threat and can suffer blistering, tongue irritation and eye problems.


We take a responsible approach towards the management of this pest and will work within the guidance set by the Forestry Commission. This will mean licensed pesticides will be applied by properly qualified and trained operators  to target the young oak processionary moth caterpillars, and prevent them from developing into a hazardous state. Only trained operators  will carry out physical nest removal when necessary.

What to do if you see Oak processionary moth

Do not approach, do not touch.

It is important to be aware of this pest. Children are particularly vulnerable as the caterpillars can be seen moving around in nose to tail processions which attracts attention. Children should therefore be taught not to approach or touch them.

Pets should be restrained from approaching the caterpillars or fallen nests.

Report it

If you see any Oak processionary nests or caterpillars (OPM) you should report them immediately.

If they are on a privately owned oak tree, report them to the Forestry Commission using their Tree Alert online pest reporting form.

If you cannot use Tree Alert, you may report them by telephone on 030 0067 442 or by email at [email protected]

If they are on a council owned tree, report it to us on 01494 732058 or please use our online contact us form.

What to do if people or animals come into contact with Oak processionary moth

It is important not to come into contact with the caterpillars, hairs or nests. The Forestry Commission has produced a leaflet with further information on how to protect yourself and what to do if you or others are affected. Further guidance can be found at Forest Research guidance.

If you think you may have been exposed and have an itching skin rash, conjunctivitis or other symptoms, see a pharmacist to relieve the symptoms. If you have a more serious allergic reaction, contact your GP or call NHS Direct on 111. The call is free from any phone. Similarly, consult a vet if your pet has a serious reaction.

Find out more about the oak processionary moth on the Forestry Commission website.