Residents of north-west and south-west London are once again being asked to help eradicate the pest oak processionary moth from the area and prevent it from spreading further.
They can do this by reporting sightings of the caterpillars or their nests to their Council or the Forestry Commission's Forest Research agency.
Oak processionary caterpillars - the larval form of the moth - threaten Britain's oak trees by eating the leaves, sometimes completely stripping them of foliage.
In addition, their hairs contain a toxin that can cause painful and sometimes serious symptoms in people and animals. For this reason people are advised not to touch the caterpillars or their nests, and to keep pets, horses and livestock away from infested trees.
This year's caterpillars have now hatched from eggs laid on oak trees last autumn. The Forestry Commission and its local partners want the public, as well as people out and about among trees in the area, such as gardeners and tree surgeons, to help by reporting sightings of the distinctive, hairy caterpillars or their equally distinctive white, silken nests in oak trees. Caterpillars and nests can then be treated and removed by suitably equipped and trained operators.
About 500 nests were destroyed last year, and more than 700 in 2007. Operators will be deployed again over the next few weeks, following up reports of sightings by treating caterpillars. Then, later in the summer, they will remove and destroy nests when any remaining caterpillars will be pupating in them before re-emerging as moths.
Roddie Burgess, head of the Forestry Commission's plant health service, said,
"The good news is that our surveys have not found any evidence that the species has spread further afield. We also believe the population has been significantly reduced, so we continue to be optimistic that we can eventually eradicate it from Britain.
"We cannot afford to relax our efforts, so now that the treatment season is here again we're asking the public once more to help us by contacting us if they think they've seen any caterpillars or nests.
"However, we do urge people not to try to deal with the caterpillars or nests themselves. Contact with them is dangerous to human health, and effective treatment requires specialist equipment and careful timing by trained operators."
Dr Brian McCloskey, regional director of the Health Protection Agency in London, added,
"If the oak processionary moth becomes established here, a lot of people might get a very itchy skin rash, and a few will get 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 efforts of the Forestry Commission and local authorities to try to eradicate this threat, and we are working closely with them.
"Advice on symptoms and treatment of people is being issued to local GPs and other health professionals.
"Anyone with a severe reaction, or who is uncertain what has caused their rash, should consult their GP."
Suspected sightings can be reported to one of the authorities below, with 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 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. Otherwise, they can be reported to the relevant Council as follows:
- in Ealing Council area, call 020 8825 5000 or e-mail trees@ealing.gov.uk;
- in Richmond upon Thames, call 08456 122660 or e-mail trees@richmond.gov.uk;
- in Brent Council area, call 020 8937 5050 or e-mail gary.rimmer@brent.gov.uk; and
- in Hounslow Council area, call 020 8583 5555 or e-mail streetcare@hounslow.gov.uk.
Meanwhile, controls on imports of oak trees to the UK have been relaxed to permit trees less than two metres tall to be imported, even if they come from areas with oak processionary moth. This relaxation follows scientists' observation that the species almost never infests trees less than two metres tall, so they can be imported provided they have been grown in a nursery, inspected before shipping, and declared free of the moth or its eggs and larvae. Previously only oak trees from nurseries free of the species, located in areas free of it, could be imported after inspection.
Further information, including pictures, and a "tree pest advisory note", is available on the Forest Research website, www.forestresearch.gov.uk/oakprocessionarymoth , and the Forestry Commission website at 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) - a native of southern and central Europe - was first idnetified on oak trees in north-west and south-west London in 2006. It most likely came into Britain as over-wintering eggs on semi-mature trees imported for planting in "instant landscaping" or screening projects. It began breeding in several locations there, including Kew Gardens.
- Nests are always dangerous to approach because of the presence of toxic hairs in them. Otherwise, the peak danger period for human health is from mid-May through June, when the hairs are most numerous.
- The caterpillars pupate in their nests in late June and early July and emerge as moths between one and four weeks later. The moths lay their eggs in oak trees in July and August, and the eggs hatch caterpillars the following spring. The caterpillars feed in groups, and at other times congregate in communal nests made of matted, white silk webbing - typically about the size of a tennis ball. The species gets its name from the caterpillars' habit of moving about in nose-to-tail processions.
- It does not necessarily kill trees - they usually recover - but it would add another unwelcome stress to Britain's oak trees, which in some areas are already suffering from other stresses such as acute oak decline and drought.
- Although a native of central southern Europe, it has become established as far north as The Netherlands over the past 15-20 years. It is possible that climate change has been a factor in its spread: milder winters and, in particular, fewer and less-severe late spring frosts which could kill emerging caterpillars, might have improved its chances of survival in more northern latitudes.
- The species will attack other broadleaved trees such as hornbeam, hazel, beech, sweet chestnut and birch, but usually only where these exist close to severely defoliated oak trees where the preferred food supply (oak leaves) is limited.
NEWS MEDIA CONTACTS:
Forestry Commission / Forest Research - Charlton Clark, 0131 314 6500 or 07810 181067; Ealing Council - Helen Mathers, 020 8825 9294; Richmond upon Thames Council - Pete Leriche, 020 8891 7136;Brent Council - Peter Kendall, 020 8937 5321 / 3054;Hounslow Council - Jini Amarasekara, 020 8583 2186;Health Protection Agency in London - Tycie West or Emily Collins, 020 7759 2834 / 24;Royal Botanic Gardens, Kew - Anna Quenby, Bronwyn Friedlander or Bryony Phillips, 020 8332 5607, pr@kew.org.