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NEWS RELEASE No: 1374223 JUNE 2010

Public help sought again in bid to rid West London of pest moth

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Oak Processionary Caterpillars

Efforts to eradicate oak processionary moths from West London are moving into a new phase, and local people are once again being asked for help.

Local residents and people who are out and about among trees in the area are being asked to report sightings of the species’ distinctive silken nests in oak trees.

The caterpillars have begun building this year's nests in oak trees in the Ealing, Brent, Hounslow, Richmond Upon Thames and Hammersmith & Fulham areas. They will retreat into the nests over the next few weeks to pupate and re-emerge as adult moths, which would then lay eggs ready for hatching next spring. The nests, typically about the size of a tennis ball, are usually white when new, but quickly become discoloured to match the colour of the tree’s bark over time. They can be found anywhere in the tree from the trunk to the main branches.

This is the last good opportunity this year for authorities led by the Forestry Commission to reduce the pest’s population. It is a forestry pest because it strips oak trees of their leaves, and it is a health hazard because the caterpillars shed toxic hairs which can cause unpleasant rashes and skin or eye irritations in people and animals.

The Commission and its partners working to eradicate the species are therefore appealing for reports of nest sightings. They will follow up the reports by arranging to have the nests removed and destroyed by specially trained and equipped operators, preferably while the larvae are pupating inside the nests.

Roddie Burgess, head of the Forestry Commission's Plant Health Service, said,

"We've done very well to contain oak processionary moth within the same general area and stop it from spreading further into Britain since it was first identified there in 2006. We’re very grateful for the help we’ve had from the public and people such as professional gardeners, tree surgeons, park staff and others who have reported sightings. We're once again asking them to help us in this way.

"We strongly advise people not to touch or try to remove the nests themselves. They can be full of the toxic hairs that the caterpillars shed, and these are a real health hazard. Children and pets should also be kept away from affected trees.

“Also, to be most effective the work needs to be done at just the right time by specially trained and equipped people, and the nests must be disposed of properly.”

Mr Burgess also asked people who were having oak trees pruned or felled in any of the affected boroughs to contact the Forestry Commission’s Plant Health Service beforehand on or 0131 314 6414 for advice about safe removal of the material.

Sighting reports should include a precise description of 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 photographs may also be sent as an aid to identification.

Sighting reports and photographs can be sent to Forest Research, the scientific research arm of the Forestry Commission, on 01420 22255 or, or to the local council or Royal Parks staff (see Notes to Editor for contact details).

Health advice - Anyone who is worried by an itching skin rash or eye irritation, and who might have been near oak trees infested with oak processionary caterpillars and their nests, should consult their GP or call NHS Direct on 0845 4647. Health information is also available from

Owners of affected oak trees can contact the Forestry Commission on 0131 314 6414 or, or their Council (see Notes to Editor), for a list of suitably qualified local pest control operators who can deal with them.

Further information is available from the Forestry Commission’s website at


1. Nest sightings can be reported to, and lists of suitably qualified pest control operators obtained from, the relevant Borough Councils as follows:

2. Oak processionary moth (Thaumetopoea processionea) gets its name from the caterpillars' habit of moving about in nose-to-tail processions. A native of southern and central Europe, it was first identified on oak trees in west London in 2006. It most likely came into Britain as over-wintering eggs on semi-mature trees imported for planting in landscaping projects. It began breeding in several locations there, including the Royal Botanic Gardens, Kew, and Richmond Park.
3. The caterpillars and their nests are always dangerous to approach because of the presence of toxic hairs, which can remain present and harmful in old nests for some years. However, the peak danger period for human health is from mid-May to the end of July.
4. 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.
5. The caterpillars do not necessarily kill trees - they usually recover - but they 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.
6. Although a native of central southern Europe, it has become established as far north as The Netherlands over the past 20 years. Climate change might have been a factor: 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.
7. The species will attack other broadleaved trees such as hornbeam, hazel, beech, sweet chestnut and birch, but usually where they are close to severely defoliated oaks where their preferred food of oak leaves is limited.
8. About 700 nests were destroyed in 2007, 500 in 2008, and 2500 last year. Last year’s increase might have been due to the very favourable conditions for caterpillars of all species in 2009, and surveyors’ growing expertise in finding them. Despite last year’s numbers, no evidence was found that the moth had spread beyond the five boroughs, and there was no significant change on 2008 in the numbers of adult males caught in pheromone traps after the nesting phase.


  • Forestry Commission / Forest Research - Charlton Clark, 0131 314 6500 or 07810 181067;
  • Ealing Council – Claire Parker, 020 8825 6551;
  • Richmond upon Thames Council - Pete Leriche, 020 8891 7160;
  • Brent Council - Peter Kendall, 020 8937 5321 / 3054;
  • Hounslow Council - Jini Amarasekara, 020 8583 2186;
  • Hammersmith & Fulham Council – Jonathan Weisgard or Rob Mansfield, 020 8753 2163;
  • Health Protection Agency - Tycie West or Emily Collins, 020 7759 2834;
  • Royal Botanic Gardens, Kew - Anna Quenby, Bronwyn Friedlander or Bryony Phillips, 020 8332 5607,;
  • The Royal Parks – Katy Murray, 020 7298 2128.