Health information about oak processionary moth

14 May 2008

The Health Protection Agency is informing people about the health effects of the caterpillars of the oak processionary moth. This follows an appeal by the Forestry Commission and, local and health authorities for residents of west and south-west London to look out for these caterpillars.

Oak processionary moth (Thaumetopoea processionea) - a native of southern and central Europe – was discovered breeding in England for the first time in 2006. It has been found on oak trees in west and south-west London, including in Kew Gardens.

The oak processionary caterpillar is in its last stages of development in late May and early June before becoming a moth; this is when it poses the most risk to human health. The caterpillar has tiny sharp barbed hairs and a toxin which can cause irritation and allergic reactions in people and animals.

Contact with the toxin-containing hairs most commonly causes intensely itchy or painful skin rashes, but can also produce sore throats, eye problems and breathing difficulties. These can happen because people touch the caterpillars or their nests, and because the wind can blow the hairs into contact with people.

Dr Roger Gross, regional director of the Health Protection Agency London, said,

"If these moths become established here, as they have in other European countries, a lot of people might get a very itchy skin rash, and a few will get more-troublesome symptoms such as itchy eyes and breathing problems.

"If they do become an on-going problem here, we would have to advise people to avoid affected oak trees during the peak months. So we welcome the work of the Forestry Commission and the local authorities to try to eradicate this threat, and we are working closely with them.

"Advice is being issued to local GPs and other health professionals to help them to identify when patients have been affected by the caterpillar hairs, and to advise them about appropriate treatment.

"Anyone with a severe reaction, or who is uncertain what has caused their rash, should consult their GP."

The Forestry Commission, working with Defra, Ealing, Richmond, Brent and Hounslow Councils, the Royal Botanic Gardens Kew, and the Health Protection Agency London, launched an action plan last year to reduce or eliminate caterpillar populations to prevent the infestation spreading out of London and becoming permanently established in Britain.

Anyone who thinks they have found oak processionary caterpillars, or their nests, should not touch them, but should report their sightings to Forest Research or Ealing, Richmond, Brent or Hounslow Council, giving as precise details as possible about the location. An Ordnance Survey grid reference is ideal, otherwise an accurate postal address with the full postcode, and/or a clear description of the tree's exact position, is helpful. Digital photos sent with emailed sighting reports can help experts to confirm the sighting. Members of the public should not attempt to deal with the caterpillars or nests themselves.

Sightings anywhere can be reported to Forest Research by telephoning 01420 22255 or by email to christine.tilbury@forestry.gsi.gov.uk. Otherwise, they can be reported to the relevant Council as follows:

In Ealing Council area, call 020 8825 5000 or email trees@ealing.gov.uk;
In Richmond Upon Thames, call 08456 122 660 or email commercialeh@richmond.gov.uk;
In Brent Council area, call 020 8937 5050 or email gary.rimmer@brent.gov.uk;
In Hounslow Council area, call 020 8583 5555 or email streetcare@hounslow.gov.uk.

Further information, including pictures and a 'tree pest advisory note', is available on Forest Research's website, www.forestresearch.gov.uk/oakprocessionarymoth, and the Forestry Commission's website at www.forestry.gov.uk/planthealth. Further health information is available from NHS Direct, 0845 4647, www.nhsdirect.nhs.uk.

NOTES TO EDITOR:

An emergency measure to protect Great Britain against further introductions of oak processionary moth came into force on the 31st March 2008. It takes the form of an amendment to the Plant Health (Forestry) Order 2005, and requires that all oak trees imported from European Union (EU) Member States are accompanied by a "plant passport". The plant passports will confirm that the trees have been grown in a nursery and that they come from an area where the place of production and its immediate vicinity have been free from oak processionary moth since at least the beginning of the last cycle of vegetation. The Forestry Commission has also asked the European Commission to draft measures to protect against further introductions, and this is likely to result in the designation of Great Britain, at least, as a "protected zone". However, because it is likely to be some time before the new EU measures can be adopted, Britain's Forestry Ministers agreed to put the amendment to the Plant Health Order in place as quickly as possible to prevent further infested oak trees entering Great Britain in the meantime.
Oak processionary moth is a native of central southern Europe, although active infestations of caterpillars have been found further north, including northern France, Belgium and The Netherlands, over the past 15-20 years. It is most likely to have entered Britain as over-wintering eggs on trees imported for planting here.
It is possible that climate change has been a factor in the expansion of its range. Milder winters and, in particular, fewer and less-severe late spring frosts, which could kill significant numbers of emerging caterpillars - might have improved its chances of survival in more northern latitudes.
The species will attack other broadleaved trees as well as oaks, such as hornbeam, hazel, beech, sweet chestnut and birch, although usually only where these exist close to severely defoliated oak trees.
The moths' populations can be very cyclic, so that a severe infestation one year can be followed by a population collapse for a number of years before the population builds up again. This has been observed in The Netherlands, where the population was very high in 1996, 2001 and 2007, but significantly lower between those years.
For further information contact the Health Protection Agency London - Claire Kennedy or Emily Collins, 020 7759 2824/2834.

Other organisations can be contacted on:

Forestry Commission / Forest Research - Charlton Clark, 0131 314 6500 or 07810 181067;
Ealing Council - Verity Adams, 020 8825 5462;
Richmond Upon Thames Council - Christian Marcucci, 020 8487 5049;
Brent Council - Michelle Hyland, 020 8937 5321, ext 1066;
Hounslow Council - Jini Amarasekara, 020 8583 2186;
Kew Gardens - Anna Quenby or Catherine Owen, 020 8332 5607.

FAQs on oak processionary moths

Last reviewed: 8 January 2009