A key phase is under way in the campaign to tackle the oak processionary moth pest in West London.
Following up on reports of sightings, pest control operators are removing and destroying nests of the oak processionary caterpillar - the moth's larval stage - from oak trees in the area while the caterpillars are congregated in their nests to pupate into moths.
This is one of the best times to deal with the pest, because the caterpillars spend up to four weeks in the nests in oak trees before emerging as moths. If any do emerge as moths, they will mate, the females will lay eggs in oak trees during the late summer, and another generation of caterpillars will emerge from the eggs next spring. The nests are typically about the size of a tennis ball, but can be larger, and are found on oak trees' trunks and branches, especially on the undersides of branches.
The species, which is believed to have arrived in Britain from Europe four years ago, is a forestry pest because the caterpillars eat oak leaves and can seriously defoliate and weaken the trees. They also pose a human and animal health problem because their tiny, barbed hairs, which can be blown about by the wind, contain a toxin called thaumetopoein that can cause breathing problems and unpleasant and potentially serious irritations to skin, ears, eyes, noses and throats. In the most serious cases they can cause anaphylactic shock.
The Forestry Commission is leading a partnership including the west London Boroughs of Ealing, Richmond Upon Thames, Brent and Hounslow, Defra, the Health Protection Agency London, The Royal Botanic Gardens, Kew, and the Royal Parks that is working together to eradicate the species before it has a chance to spread further into Britain. Roddie Burgess, head of the Commission's Plant Health Service, explained,
"A team of surveyors has been out and about since the early spring, mapping the presence of caterpillars and nests from their own observations and from reports fed to us by local and other authorities and the public.
"A number of caterpillar infestations were treated with insecticide during the spring, and now we're going after the nests while the remaining caterpillars should all be concentrated inside them to pupate.
"We continue to encourage anyone who thinks they have seen the caterpillars, or their distinctive nests of white silken webbing, to report them to our Forest Research agency or to their Council so we can arrange to have them treated.
"We found and destroyed more than 700 nests last year, and there is no doubt that this helped to limit the population of caterpillars that emerged this year. Nevertheless we do still have a major task ahead of us, with hundreds of nests mapped and due to be destroyed in the area this year."
Dr Roger Gross, Regional Director of the Health Protection Agency London, added,
"If it becomes established here, 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 it does become an on-going problem, 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 has been issued to GPs and other health professionals to help them to identify when patients have been affected by the caterpillars' 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 authorities caution that the public should not try to deal with the nests themselves because even old, disused nests can be hazardous because they can be packed with the hairs and shed skin, making their removal a specialist task for properly equipped and trained people. People should also keep their pets away from nests and caterpillars, because animals can be affected in the same ways.
Anyone who thinks they have found the caterpillars or their nests should report their sightings to Ealing, Richmond upon Thames, Hounslow or Brent Council, or Forest Research, giving as precise details as possible about the location. An Ordnance Survey grid reference is ideal, otherwise an accurate postal address, including the full postcode, and/or a clear description of the position, is helpful. Digital photos sent with emailed reports can help experts to confirm the sighting.
Sightings anywhere can be reported to Forest Research by telephoning 01420 22255 or by e-mail to christine.tilbury@forestry.gsi.gov.uk , or they can be reported to the relevant Council as follows:
Findings in Richmond Park can also be reported to the park office, 020 8948 3209.
Further information, including pictures and a tree pest advisory note, is available from www.forestresearch.gov.uk/oakprocessionarymoth and www.forestry.gov.uk/planthealth. Further health information is available from NHS Direct, 0845 4647, www.nhsdirect.nhs.uk.
NOTES TO EDITOR:
- Oak processionary moth (Thaumetopoea processionea) gets its name from the caterpillars' habit of moving about in long, nose-to-tail processions. It is a native of central southern Europe, although it has been found further and further north over the past 15-20 years, including southern Sweden, Germany, France, Belgium and The Netherlands.
- Apart from the continuing danger posed by nests full of hairs, the peak danger period for human health is from April to June, after the eggs have hatched. Nests are dealt with by being carefully removed from the trees into sealed bags and burned. Residual hairs on the tree trunks are then burned off to reduce the on-going risk of exposure.
- Oak processionary moth will attack a wide range of species of oak trees and oak hybrids. It will also attack other broadleaved trees, such as hornbeam, hazel, beech, sweet chestnut, birch and woody plants, although usually only where these exist close to severely defoliated oak trees. It does not necessarily kill trees, but it would add another stress to Britain's oaks, which in some areas are already under stress from conditions such as oak decline and drought. So from woodland owners' point of view, it makes sense to try to prevent its spread while this is still possible.
- The west London outbreak is almost certainly the result of trees infested with eggs being imported from the Continent for landscaping purposes. As a result an amendment to the Plant Health (Forestry) Order 2005 came into effect in March requiring that all oak trees imported from EU Member States be accompanied by a plant passport confirming that the trees have been nursery grown and that they come from an area where the place of production and its immediate vicinity are free from oak processionary moth. Meanwhile 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".
NEWS MEDIA CONTACTS:
- Forestry Commission / Forest Research - Charlton Clark, 0131 314 6500 or 07810 181067;
- Ealing Council - Verity Adams, 020 8825 5462;
- Richmond upon Thames Council - Ivor Jones, 020 8891 7136;
- Brent Council - Michelle Hyland, 020 8937 5321, ext 1066;
- Hounslow Council - Jini Amarasekara, 020 8583 2186;
- Health Protection Agency London - Claire Kennedy or Emily Collins, 020 7759 2824 / 34;
- Royal Botanic Gardens, Kew - Bronwyn Friedlander, Anna Quenby, or Catherine Owen, 020 8332 5607; out-of-hours press officer - 020 8332 5000.
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