A group of infested oak trees in a public area was spotted and reported to the commission last Wednesday by Bromley Borough Council, which immediately cordoned off the area and called in pest controllers.
The caterpillars eat oak leaves and in severe cases can defoliate whole trees leaving them vulnerable to other threats, said Alison Field, south-east England regional director of the Forestry Commission.
"It’s extremely disappointing OPM 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 about 2005," she said.
"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 the council and others to eradicate the outbreak.
"Tree owners should not try to remove nests themselves, as they can be full of the caterpillars’ toxic hairs. To be as effective and safe as possible this job needs to be done by trained and equipped operators, and the nests must be disposed of properly."
Sightings of caterpillars or nests can be reported to the Forestry Commission's Forest Research agency on 01420 22255; email:
firstname.lastname@example.org; or to Bromley Council's tree team on 0208 313 4471, or to the local council.
People who are having oak trees pruned or felled in affected areas must contact the Forestry Commission’s Plant Health Service beforehand on email@example.com or 0131 314 6414 for advice.