Residents advised to be aware of caterpillar pest on oak trees

NewsUpdated: 26 July 2023Trees and Landscapes

Residents of Three Rivers are being advised to be alert to the caterpillar pest Oak Processionary Moth (OPM) on oak trees.

OPM was first identified in London in 2006. The caterpillars and their nests contain hairs which can cause itchy rashes, eye and throat irritations, and should not be touched under any circumstances at any time.

You can identify their nests which are typically dome or teardrop-shaped, averaging the size of a tennis ball. They are white when fresh, but soon become discoloured and brown.

The caterpillars feed on oak leaves and can increase trees’ vulnerability to attack by other pests and diseases and can, in some circumstances make them less able to withstand adverse weather conditions such as drought and floods. A government programme is in place to limit their spread from areas where they are present.

The Forestry Commission, local authorities and landowners are working to control this pest so that residents can continue to safely enjoy local parks, gardens, and woodlands.

Cllr Chris Lloyd, Lead Member for Leisure, added: “I urge anyone who spots these OPM caterpillars to help reduce the impact of they have on human health by reporting any sightings. We are lucky in Three Rivers to have such beautiful parks, open spaces and woodlands – and we want to ensure people can go on enjoying them, so it is essential we do not allow these moths to become too prevalent.”

Report any sighting to the Forestry Commission using its Tree Alert on-line reporting form at; e-mail it to, or call 0300 067 4442.

Report any sightings on TRDC woodland and open space to TRDC at: telephone: 01923 776611

For more information on how to identify OPM, including common mistaken species, visit: