Aug 15 2019

OPM – UK wide spread, Safety bulletin – please read

Oak processionary moth (Thaumetopoea processionea) was first accidentally introduced to Britain in 2005 initially it only effected the South east of England, however by July 2019, OPM can now be found in woods across the UK. The larvae or caterpillars of OPM are a pest because they can affect the health of oak trees, people and animals. 


OPM caterpillars are most easily recognized by their distinctive habit of moving about in late spring and early summer in nose-to-tail processions from which they derive their name, and the fact that they live and feed almost exclusively on oak trees.



They can sometimes be seen processing across the ground between oak trees and clustering together as they feed on oak leaves.



The caterpillars have thousands of tiny hairs which contain an “urticating” or irritating substance. Contact with the hairs can cause itching, skin rashes and less commonly, sore throats, breathing difficulties and eye problems. The symptoms can be serious enough to hospitalize an adult.


This can happen if people or animals touch the caterpillars or their nests or if the hairs are blown into contact by the wind. The caterpillars can also shed the hairs as a defence mechanism and lots of hairs are left in the nests, which is why the nests must not be touched.


The nest may persist for years after the caterpillars have left them and must always be approached with caution.


Image from Fera Science Limited (Fera)


Woodland Trust staff & volunteers are at risk of exposure when working on or around infested oak trees.  Any Trust worker must be vigilant for caterpillars and their nests – before beginning work on or under oak trees check carefully for infestations.


Some people can become sensitized by repeated exposure to the hairs meaning that the symptoms become worse.


Health precautions

People can take these simple precautions to help minimise the health risks:



  • Touch or approach nests or caterpillars
  • Let children touch or approach nests or caterpillars
  • Let animals touch or approach nests or caterpillars
  • Try removing nests or caterpillars yourself



  • Keep any children on site away from infestations – teach them not to touch the nests or caterpillars
  • Keep pets away
  • If the Trust has cattle or other livestock in affected areas remove them as soon as possible.
  • See a pharmacist for relief from skin or eye irritations after suspected OPM contact;
  • Call NHS111 or see a doctor if you think you or someone in your care has had a serious allergic reaction – tell the doctor you suspect OPM contact;


If you find nests or caterpillars while working suspend operations immediately and move away from the area – Volunteers are asked to report any suspected sighting to the Woodland Trust Site manager.


Affected counties in England 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.


The Welsh Government have confirmed three cases in Glamorgan and Flintshire.


The Scottish Government have confirmed five cases in Angus, Edinburgh, Fife, Inverness and Lanarkshire.


To see the distribution in map form click below:



Contact your GP immediately if you have been in contact with OPM and begin to suffer symptoms – especially if you have had contact in the eye area.


Contact a vet if you believe pets or livestock may have been affected.


Any sighting of OPM must be reported to the Forestry Commission – you can do so here:


The above information can be found in PDF form here:


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