Oak trees are threatened by the caterpillars because they eat the leaves, potentially defoliating the entire tree
A new infestation of a non-native moth which is hazardous to human and animal health and trees has been identified, the Forestry Commission has said.
The oak processionary moth has been discovered in the West Wickham area of Bromley, south-east London, around nine miles from the nearest known infestations that are part of an established outbreak in west London.
But the Forestry Commission believe that the new discovery of infested oak trees is a separate outbreak rather than a natural spread from west London.
The caterpillars of the oak processionary moth, which is thought to have arrived in the UK from the Continent on imported trees, have toxic hairs which can cause itchy skin rashes and eyes and a sore throat in people and affect pet animals.
Oak trees are also threatened by the caterpillars because they eat the leaves, potentially defoliating the entire tree and leaving it vulnerable to other threats such as disease.
A group of infested oak trees in an area open to the public was reported to the Forestry Commission on July 4 by Bromley Borough Council.
The area was cordoned off to protect the public and pet animals and pest control operators were called in to remove the caterpillars and the silken webbing nests they weave at this time of year to pupate in. Other oak trees nearby are being surveyed.
Alison Field, south-east England regional director of the Forestry Commission, said: "It's extremely disappointing that oak processionary moth has been found in this part of London so far from the existing outbreak in west London, where they have become established since being accidentally introduced from Continental Europe in about 2005.
"The distance away from the west London outbreak suggests this is a separate outbreak, although we will be investigating the pathway by which it got to Bromley. We are working with Bromley Council and others involved to eradicate the outbreak as quickly as possible."
The Forestry Commission warned tree owners not to try and remove nests themselves as they can be full of the toxic hairs, and said people having oak trees pruned or felled in the affected areas should contact them first for advice.