People in parts of London, Surrey and Berkshire are being reminded not to touch the nests which oak processionary caterpillars could be building in oak trees in these areas.
They are also being advised to protect animals from contact with the nests, and to report sightings to the Forestry Commission or local Councils.
This is because the nests contain thousands of the caterpillars’ hairs, which contain an irritating substance which can cause unpleasant skin rashes and, sometimes, eye and throat irritations in people and animals. They are also a tree pest because they eat oak leaves: large numbers can strip oak trees bare, leaving them weakened and vulnerable to other threats.
The caterpillars are the larval stages of the pest oak processionary moth (OPM), and in June they build distinctive white, silken, webbing nests and trails on the trunks and branches of oak trees. The nests become discoloured after several days.
There are three separate outbreaks of the pest: one in several boroughs in West and South-West London and the Elmbridge and Spelthorne areas of Surrey; one in the Bromley/Croydon area of South London; and one in the Pangbourne district of West Berkshire. Each outbreak is thought to have begun with a separate accidental introduction as eggs on semi-mature oak trees imported from continental Europe.
Ian Gambles, the Forestry Commission’s Director England, encouraged local people to help tackle the pest by reporting sightings of the nests and caterpillars, but not to touch or approach them: “We want to keep our woods and parks safe for everyone to enjoy, and the public can help us by reporting OPM nests and caterpillars to us or their local council so that they can be properly removed. We also advise people against trying to remove the nests themselves, even if they own the oak tree. To be as effective and safe as possible, this job needs to be timed just right and done by people with the right training and equipment, and the nests must be disposed of properly.”
Dr Deborah Turbitt, London Deputy Director of Health Protection for Public Health England, endorsed the ‘don’t touch’ message, adding: “We strongly advise people not to touch or approach the caterpillars or their nests because of the health risks. Pets can also be affected, and should be kept away as well. The Forestry Commission’s website has pictures to help the public to identify OPM, at www.forestry.gov.uk/opm. “We advise people to 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 pets are affected. We have issued advice to local GPs and health professionals to help them identify when patients have been affected by contact with OPM hairs, and to advise them on appropriate treatment.”