Moths on Oaks - OPM vs Green Oak Tortrix

For many years we have been advising you to be careful around Oak trees, particularly when the caterpillars of the Oak Processionary Moth (OPM) start to appear in early spring. We are really pleased that the message is getting out there and visitors do call us to to let us know when they find a nest that we might have missed - on a site this size, your eyes and ears on the ground are a really big help to our staff.

Aside from OPM, there are several species of moth that feed on the Oak trees and this year there has been a mass emergence of a second species that favours the Oak - the Green Oak Tortix - and many of you have called or e-mailed us with concerns about these moths, believing them to be the Oak Processionary Moth.

Please be assured that the Green Oak Tortrix moths are harmless.  They are a very common moth in many parts of Britain and although the larvae can become a pest, they have never become a problem for our Oak trees here on the Commons.  You will recognise the larvae as the small green caterpillars that always seem to hang at head height during March/April and tangle themselves in your hair!

The reason for this mass emergence is unclear but it could be weather-related or perhaps a lack of parasites/predators last year, or a combination of factors.  But shake an Oak tree and you will be surrounded by a cloud of this beautiful little moth!

 

A few OPM facts: 

Whilst we're talking about Oak Processionary Moth, there has been a lot of press about them recently, some of it slightly sensational, with headlines such as "Toxic caterpillar outbreak across southern England" and "An outbreak of toxic caterpillars have descended on London".

Here are a few facts to clear that up:  

  • OPM arrived in London at least 10 years ago, so it's been here a while and hasn't just "landed"..
  • It is not toxic, that would indicate it is poisonous which it isn't. What it has are urticating hairs which are an irritant, but they won't poison you.
  • Do you still need to take care?  Yes.  You, your children and your pets should be careful around oak trees as the hairs of the caterpillars can cause irritation if touched or inhaled. The caterpillars started to appear in mid-April and will be present until they pupate into moths around July time. 
  • You will not usually see the moths as they will generally only fly at night and, if you do, they are not dangerous.
  • The hairs and pupae cases that the caterpillars leave behind can still be irritating so if you do see any that you believe are a hazard to the public, please call us and let us know.  Do not try to remove them yourself.

 

 

If you have any concerns or queries about any wildlife you see on the Commons, do call us on 020 8788 7655