People are being urged to watch out for dangerous caterpillars during the warm weather.

With temperatures set to reach 26C this weekend, sunseekers enjoying the outdoors have been asked to keep an eye out for the tree pest oak processionary moth caterpillars.

These creatures contain hairs which can cause itchy rashes and eye and throat irritations. They should avoid being touched in all circumstances.

They can be identified by their nests that are typically dome or teardrop-shaped, averaging the size of a tennis ball.

The creatures are white when fresh, but soon become discoloured and brown.

They feed on oak leaves and can increase trees’ vulnerability to attack by other pests and diseases, making them less able to withstand adverse weather conditions such as drought and floods.

The greatest risk period is May to July, when the caterpillars emerge and feed before pupating into adult moths.

Three Rivers District Council has urged anyone who sees the creatures in the district to report sightings to the Forestry Commission.

The Forestry Commission, working in partnership with others, has an annual programme in place to tackle the pest, with an ongoing programme of surveillance, treatment and research.

Andrew Hall, Forestry Commission operations manager, said: “At this time of year, many people are enjoying green spaces and it’s really important for the public to be aware of the risk of tree pests like oak processionary moth and to report any sightings via our TreeAlert website or by calling the Forestry Commission. This will help us with our programme of treatment and enables us to slow the spread of this pest.”

Cllr Chris Lloyd, lead member for leisure at the council, added: “Our award-winning open spaces and parks are very popular with local communities and visitors. People use them for exercising, relaxing and picnics too. Controlling these pests will help preserve our woodlands and communities can keep enjoying using these open spaces.

“Please help reduce the impact of OPM caterpillars on human health by reporting any sightings immediately. Do keep alert, stay safe, keep healthy, and observe the social distancing rules currently in place by keeping two meters apart.”

You can report any sightings to the Forestry Commission via its Tree Alert online portal, email opm@forestrycommission.gov.uk or you can call them on 0300 067 4442 with a precise description of the tree’s location.