Currently Effected Counties

  • OPM is established in most of greater London and surrounding counties.
  • Affected English counties include Cambridgeshire, County Durham, Devon, Dorset, Essex, Gloucestershire, Greater Manchester, Hampshire, Hertfordshire, Kent, Lancashire, Leicestershire, Lincolnshire, London, Merseyside, Middlesex, Nottinghamshire, Oxfordshire, Southampton, Staffordshire, Suffolk, Surrey, Warwickshire, West Midlands, Wiltshire and Yorkshire.

Wales & Scotland

  • The Welsh Government confirmed three cases in Glamorgan and Flintshire,
  • The Scottish Government confirmed six cases, in Angus, Edinburgh, Fife, Glasgow and Inverness

Mainland Europe

  • OPM is established in southern, central and Western Europe, northern Germany and The Netherlands.

Its effect on trees

  • The caterpillars of OPM feed on the leaves of several species of oak trees.
  • Serious infestations of OPM caterpillars can strip whole oak trees bare,
  • Serious damage can cause severe stress in times of drought. Also leaving trees more vulnerable to other pests and diseases.

Threat to people

  • Older caterpillars develop tiny hairs.
  • The hairs can cause itching skin rashes and eye irritations, sore throats, breathing difficulties and, rarely, allergic reactions in people and animals.
  • The risk of exposure to these hairs is highest in May and June.
  • The caterpillars will shed their hairs when disturbed/threatened.
  • The caterpillar’s hairs can be blown by the wind.

Vulnerable people and animals

  • Curious children and pets;
  • People who work on or close to oak trees;
  • People spending time close to infested trees.
  • Grazing/browsing livestock and wild animals – close to infested trees.


  • The actual moth is brown.
  • The caterpillars have very long white hairs with a grey body and dark head.
  • Caterpillars move around in processions during late spring and early summer.
  • The caterpillars can be seen on the ground between oak trees.
  • The caterpillars feed in clusters.
  • The nests are made of white silk webbing and can be found at ground level or very high up in the tree.
  • A Silk trail along the trunk of an Oak tree is a sign of OPM infestation.

What can be done?

  • The Forestry Research encourages the following mantra:
  1. Spot it
  2. Avoid it
  3. Report it