Oak processionary caterpillar nests warning

Residents and visitors in west London are being reminded not to touch the nests which oak processionary caterpillars are building in oak trees.


They are also being advised to protect animals from the nests, and to report sightings to the Forestry Commission or Ealing Council.

This is because the nests can contain thousands of the caterpillars’ hairs, which have an irritating substance called thaumetopoein, which can cause painful skin rashes and, sometimes, eye and throat irritations in people and animals.

The caterpillars are the larval stages of the pest oak processionary moth (OPM), and June is the time of year when they build their distinctive white, silken, webbing nests on the trunks and branches of oak trees. They also make long, white trails of silken webbing on the trees. They retreat into the nests between feeding sessions, and, later in the summer, to pupate into adult moths.

They are also a tree pest because they eat oak leaves, and large populations can strip trees of their leaves, leaving them weakened and vulnerable to other threats.

Councillor Bassam Mahfouz, Ealing Council’s cabinet member for transport and environment, said: “Residents are encouraged to report sightings of nests or caterpillars in their garden or in a public area. We also urge residents not to attempt to remove the pests themselves as it requires a specially trained and equipped team to do it at the right time and to dispose of them correctly.”

Dr Yvonne Doyle, London regional director of Public Health England, endorsed the ‘don’t touch’ message. She said: “The nests can be full of irritating hairs, even after the moths have emerged, and the irritating substance in the hairs can remain active for a long time. The hairs can be blown about by the wind, so it’s important that people and animals do not touch or go near the nests.

“Anyone who experiences an itchy or painful skin rash or a sore throat and irritated eyes after being near oak trees in these areas should consult their GP or NHS 111, who have been given advice about recognising the symptoms and appropriate treatment.”

The nests are typically about the size of a tennis ball. They are usually white when new, but become discoloured to match the colour of the tree’s bark, and can be found anywhere in the tree from the trunk to the main branches. However, they can fall to the ground, where they can be accessible to children and inquisitive animals such as cats and dogs.

Guidance on identifying OPM is available on the Forestry Commission’s website at www.forestry.gov.uk/opm

* Sighting reports – can be sent to the Forestry Commission using the Commission’s Tree Alert app or on-line form, available from the above website page, or to Ealing Council by emailing trees@ealing.gov.uk or phoning 020 8825 6611.

* Health advice – Anyone who is worried by an intensely itchy or painful skin rash, sore throat or irritated eyes, and who might have been near oak trees infested with OPM, should consult their GP or NHS 111. Health information is also available from the Public Health England website (http://www.hpa.org.uk/) under ‘Oak Processionary Moth’. Anyone concerned about their pets should contact a vet.

* Pest control – A list of local operators who can deal with OPM is available from the Forestry Commission on 0131 314 6414 / plant.health@forestry.gsi.gov.uk

* Working on oak trees – Anyone having oak trees pruned or felled in the affected areas must contact the Forestry Commission’s Plant Health Service beforehand on plant.health@forestry.gsi.gov.uk or 0131 314 6414 for advice about safe removal of the material.