Nests removed and destroyed after oak processionary caterpillar found in Watford

Updated: 3 August 2016

Tree pest nests are being removed and destroyed in Watford after oak processionary moth (OPM) caterpillars were found in the area this week...

Tree pest nests are being removed and destroyed in Watford after oak processionary moth (OPM) caterpillars were found in the area this week.

People are being advised not to touch the caterpillars and nests, to keep animals away from the pests, and to report sightings to the Forestry Commission.

OPM can affect trees, people and animals, and was first discovered in England in London in 2005. Tree and public health authorities in Hertfordshire have been preparing for the possibility of its spreading into the county.

The caterpillars shed thousands of their tiny hairs in the nests, and these can cause itchy skin rashes and eye irritations. In extremely rare cases, they can cause breathing difficulties in people and animals. The caterpillars eat oak leaves, leaving infested trees weakened and vulnerable to other threats.

Steve Scott, the Forestry Commission’s East England Director, encouraged local people to help tackle the pest by reporting sightings of the nests and caterpillars, but not to touch or approach them:

“We want to keep our woods, parks and gardens safe for everyone to enjoy, so we are removing the nests immediately, and surveying oak trees in the surrounding area to check whether there are any more. The public can help us by reporting OPM nests and caterpillars to us so that they can be properly removed. However, please don’t try to remove the nests yourself. They need to be removed by people with the right training and equipment, and disposed of properly.”

Mr Scott added that protecting the country from plant and tree diseases is important for our economy, the environment and our health. The Government is committed to protecting our borders from pests and diseases and building the resilience of our trees and plants, and it has invested more than £21 million into tree health research.

Jim McManus, director of public health for Hertfordshire, said: "The key risk to pets and humans is the hairs from the caterpillars, so we strongly support the 'don't touch or approach the nests or caterpillars’' advice from the Forestry Commission. People should also keep their pets and livestock away. We have issued advice to local GPs and health professionals and to accident and emergency departments to help them identify when patients have been affected by the caterpillars, and to advise them on treatment.”

- Health advice is available from the “Insects that bite or sting” area of the NHS Choices website, .

- Sighting reports can be made to the Forestry Commission by email to .

- Anyone having oak trees pruned or felled in the affected areas must contact the Forestry Commission on  or 0300 067 4442 for advice about safe removal of the material. Good practice guidance for tree surgeons and pest control operators is available at