Oak processionary moth (OPM)

Summer update on Oak Processionary Moth (OPM) - July 2020

OPM has spread significantly across the borough in the last few years and is now firmly established in northern Surrey and will be for the foreseeable future. 

What does OPM look like?

OPM is a tree pest. Its caterpillars feed on the leaves of several species of oak trees. They generally affect only oak trees as they cannot complete their development on other tree species. They have long, white hairs, a grey body and dark head. Older larvae have a central dark stripe with paler lines down each side. They build white silk-type nests in the branches or trunks of trees (not in the leaves). They can be spotted on tree trunks moving about in late spring and early summer (May, June and July) in nose to tail processions – hence their name. Lines of caterpillars are often arrow headed. They can sometimes be found on the ground moving between trees in this procession.

What should you do if you spot an OPM nest or caterpillars?

  • Make sure you have correctly identified the species: information is available on YouTube or on our OPM webpage

  • Stay away for your own safety. OPMs can cause skin and eye irritations, sore throats, breathing difficulties and, in some very rare cases, allergic reaction in people and animals who come in contact with them.

If the sighting is on private land:

It is the responsibility of the land owner to look at individual trees and decide what is the appropriate management needed.

If you spot an OPM case on council-owned land:

  • The case might have already been reported: look out for posters displayed at affected sites. Do not ignore them. Stay away for your own safety.

  • Report it to us on 01372 474825, 01372 474579 or by email at opm@elmbridge.gov.uk

What can the council do about OPM?

We aim to manage the risk posed to visitors and residents on our own tree stock (i.e. located on council-owned land), as it is not possible to manage OPM for eradication from the borough. We will risk assess trees which show signs of infestation and, depending on the hazard posed, we may arrange nest removal during June/July/August. Not all nests will be removed in an area where contractors are engaged, especially if they are away from direct contact with the public. Currently we are working with contractors to remove nests which are seen as posing a high risk, particularly those on boundaries with residential gardens.  

For further information or to report any sightings, email opm@elmbridge.gov.uk or call 01372 474579.

Date published: 6 July 2020

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