Oak Processionary Moth Treatment

Oak processionary moth (Thaumetopoea processionea, OPM) is a native of southern Europe accidentally introduced into Britain in 2005 due to the trade of live plants.

The outbreak was contained within London for some years however, they are now moving remorselessly outwards into the Home Counties. The OPM caterpillars feed on oak leaves and cause significant damage to the integrity of the tree.

The caterpillars have distinctive long white hairs emerging from reddish warts along their bodies, a single dark stripe down their backs and a whitish line along each side. Their hairs are irritating and can cause skin problems, conjunctivitis, respiratory congestions and asthma in humans, wildlife and pets. Contact with dead larvae, cocoons, nests and debris-infected oak trees can cause dermatitis and other symptoms.

Effective treatment includes cutting out, vacuuming or burning of nests during the day when most caterpillars are in the nest. Chemical applications can also be effective.

Treatment of Oak processionary moth, or OPM, should only be carried out by an appropriately trained professional.

What to do if you see a nest?



  • Touch or approach OPM nests or caterpillars
  • Let children or animals touch or approach nests or caterpillars
  • Try and remove nests of caterpillars yourself


  • Immediately call Maydencroft. We will be able to confirm and remove infestation or point you in the right direction for additional help.
  • Report the sighting to the Forestry Commission Tree Alert System (
  • Keep a safe distance from the tree and other trees in the vicinity and encourage others to follow suit.