OPM spreading North of London

Oak Processionary Moth

The oak processionary moth (OPM) is increasing in abundance throughout Hertfordshire and we are getting increasing enquiries here at Maydencroft. Here is everything you need to know about OPM and what to do if you find it on your land.

What is OPM?

The oak processionary moth is a non-native species whose caterpillars feed on oak leaves and cause significant damage to the integrity of the tree. The species was accidentally introduced to the UK in 2005. Larvae follow each other nose to tail in a long processionary line between the nest and feeding areas which give them their name. 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.

Allergic reactions to mature caterpillar hairs are frequent as they contain a harmful chemical causing rashes, conjunctivitis and respiratory problems. Health problems can even occur when there is no direct contact with the caterpillars as their hairs fall off very easily. Abandoned nests will contain lots of hairs and shed skins and should be treated with due care.

Treatment for OPM

Effective treatment includes cutting out, vacuuming or burning of nests during the day when most caterpillars are in the nest. Chemical application can also be effective but only at early stages when larvae are constantly feeding. Treatment of OPM should only be carried out by an appropriately trained professional.

What to do if you see a nest? ‘SPOT IT, AVOID IT, REPORT IT’


Touch or approach OPM nests or caterpillars; Let children or animals touch or approach nests or caterpillars; Try and remove nests or caterpillars yourself.


Immediately call an arborist or pest control expert to confirm and remove infestation; Report the sighting to the Forestry Commission.

Maydencroft Limited have extensive knowledge of OPM and have successfully removed several OPM nests from the local area. If you find any evidence of OPM on your land and need the nest confirming and removing then please ring Patrick Venables, our tree pests and diseases expert on 01462 658764.