Oak processionary moth

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Oak processionary moth caterpillar (Photo: WTML)

Oak processionary moth caterpillars feed on the leaves of oaks causing serious leaf loss (Photo: WTML)

This non-native moth has been found in London and Berkshire. It causes a risk to human health as well as seriously damaging trees.

What are oak processionary moths?

The oak processionary caterpillars’ tiny hairs contain a toxin which can lead to itching skin lesions and, less commonly, sore throats, breathing difficulties or eye problems. This can happen if people touch the caterpillars or nests, or if the hairs are blown into contact by the wind. 


  • Caterpillars feed on oak leaves leading to severe loss of foliage but not usually fatal
  • Weakening of the trees can make them more vulnerable to other diseases


  • Caterpillars of the oak processionary moth (Thaumetopoea processionea), a native of central and southern Europe. (See Forest Research guide to distinguishing it from similar native species.
  • Probably entered Britain as eggs laid on young trees imported from Europe for planting here.


  • Found in 2006 in London and now breeding in several locations in south and west London, and in Pangbourne, west Berks.
  • Milder weather and reduced late frosts could enable the moth to survive and breed further north than its traditional native range. Likely that it could survive and breed in much of England and Wales

Report it

If you think you’ve spotted this disease please inform the Forestry Commission using the Tree Alert reporting tool. Three good-quality digital photographs are required to aid identification.

For further information visit the Forestry Commission.

Trees face huge challenges

With more new pests and diseases reaching our shores tackling pests and diseases is now an urgent priority

Learn about the threats