An infestation of caterpillars, which are hazardous to humans, has been discovered in the West Wickham area of Bromley.
The oak processionary moth is not native to this country, although it has already been found in parts of west London.
The Forestry Commission says the new infestation is around nine miles from any other known colony.
The moth caterpillars have toxic hairs which can cause itchy skin, rashes and sore throats. They are also a threat to native plants, because they devour huge quantities of leaves.