The Forestry Commission today urged the public to report sightings of oak processionary moth (OPM) caterpillars.

Oak processionary moth, which is a tree pest, was first identified in London in 2006 and has since spread to some surrounding counties. The caterpillars and their nests contain hairs which can cause itchy rashes, eye and throat irritations, and should not be touched under any circumstances.

The greatest risk period is May to July when the caterpillars emerge and feed before turning into adult moths.

The pest is established in London and surrounding areas although most of Britain has Pest Free Area status, meaning the pest is not known to be present in much of England.

The Forestry Commission runs an annual programme in place to tackle OPM, and works with partners to monitor, treat and research the pest, in order to slow the spread and reduce the intensity of the pest.

Andy Hall, Forestry Commission Operations Manager, said:

At this time of year, many people are enjoying green spaces and it’s really important for the public to be aware of the risk of tree pests like oak processionary moth and to report any sightings via our TreeAlert website or by contacting the Forestry Commission.

This will help us with our programme of treatment and enables us to slow the spread of this pest. Any sightings should be reported to the Forestry Commission via its Tree Alert online portal. Alternatively, people can email opm@forestrycommission.gov.uk or call 0300 067 4442.

Trish Mannes, Deputy Director for Health Protection for Public Health England South East, endorsed the ‘don’t touch’ advice, saying:

We strongly advise people not to touch or approach the caterpillars or their nests because of the health risks posed by the hairs. Pets and livestock can also be affected and should be kept away as well. The Forestry Commission website has pictures to help identify the pest.

People should 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 animals are seriously affected.

OPM caterpillars feed on oak leaves and can make trees more vulnerable to attack by other pests and diseases, making them less able to withstand adverse weather conditions such as drought and floods. A government programme is in place to limit their spread from areas where they are present.

Since 2012, the government has invested more than £37 million in tree health research; this includes a dedicated programme of research on oaks and the pests that threaten them, such as oak processionary moth.

How to identify OPM caterpillars

  • Nests are typically dome or teardrop-shaped, averaging the size of a tennis ball. They are white when fresh, but soon become discoloured and brown. The caterpillars have black heads and bodies covered in long white hairs which contain proteins which 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.
  • More information on how to identify OPM, including common mistaken species.

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Public urged to report sightings of tree pest oak processionary moth caterpillars

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