A resident on one of the roads backing onto Putney Heath messaged us a photo of a grey, silky nest low down on an oak trunk, asking whether it was safe to knock off with a broom. It wasn’t, and it still isn’t. South west London sits right in the core zone for oak processionary moth, which has been established here since it first arrived from Europe in 2005, and Putney’s mature oaks along the Heath and around Wandsworth Park are exactly the kind of tree it favours.
The caterpillars carry thousands of tiny hairs containing a substance called thaumetopoein, which causes skin rashes, eye irritation and sore throats in people and pets who come too close — and the hairs stay irritant in old nests long after the caterpillars themselves have moved on. That’s why we don’t recommend anyone without the right training and PPE goes near a nest, however tempting it is to just clear it yourself.
Removal has to be done by someone trained to handle OPM safely: full protective coveralls, respirator, and nests bagged and disposed of as controlled waste rather than left on the ground or composted. We report confirmed finds through to Forest Research as part of the wider monitoring picture, because tracking where the moth is spreading matters as much as dealing with any one tree.
While we’re up assessing an oak for OPM we’ll usually flag any other work worth doing at the same time — crown lifting over a drive, or deadwooding where a limb’s carrying more weight than it should.
We’ve been doing tree surgery across Putney and the rest of south west London for 20 years, and if you’ve spotted a nest or just want a tree looked over before autumn winds pick up, get in touch through putneytreesurgeons.co.uk/.
