The Oak Processionary (Thaumetopoea processionea)

We provide recommendations for Tree Officers and others who manage trees and woodlands in London, to help them formulate search and treatment plans and to understand the background to this serious pest.

The area affected by OPM is growing steadily. It seems possible that attempts to eradicate the pest may fail. Our Guidance Note also describes the reasons why, despite the hard work and effort put in by many organisations and individuals, we may be on the brink of failure.

At present this is generally considered as an issue of plant health. Should eradication fail and the pest continue to spread, the LTOA believes that the human health problem will belatedly have to be recognised at considerable potential cost.

At present, eradication may still be possible. The time to deal with the pest is now.

Dave Lofthouse, Chair of the LTOA, said “We are providing our members with the best tool we can devise to help them plan front-line action but resources will be the other key to success".

Click here to view or download the OPM Guidance Note from our document repository


Latest News

Oak Processionary Moth Programme Update, 2 November 2015

OPM surveillance and control work has been completed for the year. More than 250 sites known to be infested in the control zone were treated with insecticide during the spring, and more than 50,000 trees were surveyed for nests and caterpillars during the summer.

A total of 359 Statutory Plant Health Notices (SPHNs) requiring removal of infestations were issued in the control (outer) zone, and most of this work was done under the Defra-funded pilot programme.

Thank you to those who have provided reports of survey and control work in the core (inner) zone, and we would still appreciate any outstanding reports. Having as full a picture as possible is a real aid to monitoring and planning effective control programmes.

OPM was found in new areas during the year, including North-East London and the Guildford District of Surrey (see attached map), but we remain confident that the control programme has continued to limit its population, impacts and rate of spread.

Pheromone trapping

An extensive pheromone trapping programme followed in late summer around the peripheries of the London/Surrey outbreaks, in the Pangbourne area of west Berkshire, and along a ‘corridor’ between the West London and Pangbourne outbreak areas. About 900 traps were deployed. The traps catch mature male moths, and the results (see attached document) can provide useful intelligence about changes in the distribution of the species.

Programme review

A well attended meeting of many of the partners involved was held in London on October 13 to review the 2015 programme, and to identify what worked well and what needs to be changed. The results will inform our programme planning for 2016. Speakers included the Chief Plant Health Officer, Professor Nicola Spence, and we are very grateful to Professor Spence and all those who attended and contributed to this useful event. We are now planning the 2016 programme, and Defra and the Forestry Commission have briefed the government minister with responsibility for tree health.

Tree surgery

May I remind everyone that if you are planning tree surgery on Oak trees during the Winter, please be sure to follow the Good Practice Guide to avoid accidentally spreading Oak processionary moth.

The guide can be found at the following here

Keeping you informed

This will be the last OPM Update for 2015, and we expect to resume them in Spring 2016, or earlier if there are developments in the meantime which we would like to share with you. Thank you everyone who has contributed time, skills and resources to this year’s programme – OPM can only be effectively controlled by strong partnership working, and your contributions are much appreciated. Meanwhile, please do contact us at any time at the email address below if there is anything you wish to know or discuss.


Pheremone Traps - Results

Nest Survey Status


Andrew Hoppit

OPM Project Manager

This email address is being protected from spambots. You need JavaScript enabled to view it.

The LTOA website is sponsored by:

How to Become a Member

Members can attend, for free, the LTOA meetings which are held four times a year and cover a wide range of tree related matters.

Click here to find out how to become an associate member