Oak Processionary Moth (OPM)

Oak Processionary Moth (OPM) Caterpillars
OPM caterpillars

Oak Processionary Moth (OPM) was accidentally introduced and first discovered in the borough of Richmond, London back in 2006.  From there, it has slowly spread out from London and now threatens the Guildford and Waverley Areas.

OPM has become a major invasive defoliator of Oaks in the South East.  The caterpillars feed on a variety of Oak species throughout the summer months.  As the caterpillars develop, they produce thousands of tiny urticating hairs that cover their body, these hairs contain toxins.  As the caterpillars grow, they amass in nests throughout the crown of a tree.  These nests ultimately accumulate huge quantities of these toxic hairs.  Nests vary in size and can be difficult to spot at times.

Oak Processionary Moth (OPM) Caterpillars Nest
OPM Nest


Contact with the hairs can cause itching skin rashes, sore throats, breathing difficulties and severe eye irritations.  In some cases, contact with the hairs can cause life-threatening allergic reaction.

Physical contact with a nest and the caterpillars should be avoided at all cost.  It is not only people that are at risk, but dogs and cats will suffer the same effect if they are exposed.

Oak Processionary Moth (OPM) Caterpillars contact with skin
OPM skin irritant

If you spot or suspect a nest in your tree, DO NOT:

  • Touch or go near nests or caterpillars.
  • Let children or animals touch or go near the nests or caterpillars.
  • Try to remove nests or caterpillars yourself.

Instead, DO:

  • Call in a suitably qualified arborist or pest control expert to remove infestations from your trees. Dryad are suitable qualified to carry out this task.
  • Inspect your Oak trees regularly for signs of OPM presence.
  • Teach children not to touch or go near the nests or caterpillars.
  • See a pharmacist for relief from skin or eye irritations after possible OPM contact. Tell the pharmacist you suspect OPM contact.
  • Call NHS111, go to an accident and emergency clinic, or see your GP if you think you or someone in your care has had a serious allergic reaction. Tell the doctor you suspect OPM contact.
  • Alert any neighbours who have Oak trees in case they also have an OPM infestation.


Our operatives are fully trained and experienced professionals.  Before removing OPM nests, operatives will dress in full Personal Protective Equipment (PPE) including Hazmat suits, high-efficiency respiratory protection and eye protection.  It is essential that the operator is fully protected and safe during the removal of these toxic pests.

To remove the majority of the nests from a tree, we use high capacity, powerful industrial vacuums with HEPA grade filters.  This significantly reduces potential exposure from the toxin and removes more traces of the nest from the tree.  Where the vacuum cannot be used, we resort to manual removal of the nests using hairspray to first “fix” the nest and hairs together, and then physically remove the nest into a plastic bag where it is sealed and then double bagged.

Once the nests have been removed from a tree or site, the client will be provided with a consignment note stating where the hazardous waste will be taken.

The nests and all contaminated arising waste is disposed of responsibly.  The waste is destroyed by incineration using a licensed third party waste carrier.


If you have concerns regarding possible OPM in your trees, please contact us today for advice.


For further information on this topic please visit the Forsrety Commission Website.


Dryad Tree Specialists Ltd, Hesters Yard, Oak Hill, Wood Street Village, Guildford, Surrey, GU3 3ET.