People in parts of London and Surrey are being reminded not to approach caterpillars of the oak processionary moth (OPM), which are now emerging in oak trees in these areas.
They are also advised to keep children and animals away from the caterpillars and their nests, because the caterpillars’ hairs can cause itching skin rashes and other health problems. The public is also urged to report any sightings.
Affected areas include boroughs in West and South-West London, Bromley and Croydon and southern parts of Lewisham in South London, and Elmbridge and Spelthorne in Surrey.
OPM caterpillars are a tree pest which was accidentally introduced to Britain. They feed on oak leaves, and in large numbers they can severely defoliate trees and leave them vulnerable to other pests and diseases.
Their tiny hairs contain a protein which can cause itchy skin rashes and, less frequently, eye and throat irritations and breathing difficulties in people and animals. The hairs can be blown on the wind, and left in their nests in and under oak trees. The greatest risk period is May to July, although nests should not be approached at any time.
The Forestry Commission, councils and land managers are tackling the pest with a carefully controlled programme of tree treatment and nest removal. Ian Gambles, the Forestry Commission's Director England,
said the public could play an important role in helping to control the pest by reporting sightings, but advised caution.
“We need reports of the caterpillars or their nests from the public or others, such as gardeners, tree surgeons and ground-care workers, who work or relax near oak trees,” he said.
“However, they should not try to remove the caterpillars or nests themselves. This needs to be carefully timed to be effective, and is most safely done by specially trained and equipped operators.”
Mr Gambles explained that extra surveying last year had revealed a greater outbreak area than was previously known, so the Commission had had to focus its control effort on the outer boundaries of the outbreak areas to limit spread of the pest and protect unaffected areas. He added:
“We are therefore encouraging oak tree owners and local authorities to continue helping to minimise the population and impacts in the core areas by finding and removing infestations.
“Many of them have given us strong support for several years, but we have produced on-line guidance to help those who are dealing with this pest for the first time.”
Dr Deborah Turbitt, Deputy Regional Director for Health Protection, London, 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 can also be affected, and should be kept away as well. The Forestry Commission website has pictures to help identify the pest.
“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 affected.
“We have issued advice to local GPs and health professionals to help them identify when patients have been affected by the caterpillars and to advise them on appropriate treatment.”
Trees are treated by fully qualified operators under strict health, safety and environmental controls to ensure it is safe for people and animals.
Sightings must be reported to the Forestry Commission, preferably with its Tree Alert on-line form available from www.forestry.gov.uk/opm
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