Oak Processionary Moth

Oak Processionary Moth Pest

The caterpillar of the oak processionary moth is highly poisonous, is causing a severe threat to thousands of our oak trees, along with also being potentially toxic to humans, pets, livestock and other animals.

Tremendous efforts have been made to cull the oak processionary moth without success and unfortunately the oak processionary moth also has very little in the way of any natural predators in Great Britain.

Having first being identified back in 2006 in Richmond (who have,  incidentally, spent £200,000 plus trying to eradicate them), they have now managed to establish themselves successfully in several parts of London. In particular the boroughs of Richmond, Wandsworth, Hounslow, Ealing and Brent and due to the unsuccessful culling attempts, this has left the experts with having to result to containment as the only other method of control to try and prevent the moth from spreading to other areas of the country.

Oak tree species affected include English, Turkey, and Sessile.


Oak Processionary Moth Description & Background Information

A native of central and southern Europe it is thought the oak processionary moth was imported, most probably as eggs laid on oak trees, brought over from the continent back in 2006.

Oak processionary moth caterpillars have a brown body and a dark coloured head when first hatched but this colour lightens as they start to grow.  They are also covered in thousands of tiny hairs, along with very noticeable, long white hairs making for a marked contrast.  The hairs contain a toxin called thaumetopoein which may cause an irritating rash on the skin and in extreme cases can also cause eye problems, sore throats and even difficulties in breathing, particularly to people with breathing problems such as asthma, so do avoid even touching one.

The hairs are shed as a defence mechanism. The oak trees then becoming covered in these tiny, unnoticeable hairs, posing a potential risk to anyone touching the trees and because the hairs are also easily dispersed by the wind and then carried further afield. Of course, you do not need to be that close to an oak tree to be at risk of coming into contact with the hairs, including inhaling them.

The caterpillars also cause untold damage to oak trees, feeding rampantly on their foliage thereby causing devastating defoliation, this, in turn, weakens the trees thus making them vulnerable to becoming infected with various other diseases and even possible death.

Oak processionary moth caterpillars can easily be recognised in about early spring to early summer when they start moving around in a nose to tail procession (hence the name) and you may also notice their nests on the branches and trunks of oak trees.   These nests usually start to appear in early summer and when newly built are white and silky, along with white silky trails to be found in the trunk and branches, although they soon become discoloured making them harder to see.

If you see a nest under no circumstances should you touch or try to remove it yourself.  Apart from causing a potential health risk to yourself or others around you, you may also cause the problem to be spread.  These nests need to be removed and destroyed by qualified professionals.

Should you see one in a public place, then please do report it immediately to your local authority. If you see one in an oak tree in your garden then get in touch with a local tree surgeon, many are used to dealing with them as they come across them when pruning oak trees and lots also offer nest removal as one of their services.  In any event, they will certainly be able to advise you as to what steps you need to take.

As for recognising the adult moth, they are a very undistinctive brown colour and look just like any other harmless moth.  You may be able to identify them better when they start to become active from the middle to late summer, hovering around oak trees looking for suitable places on branches and twigs where they will lay their eggs.

It should be noted that, as the name suggests, the oak processionary moth tends to contain itself to only oak trees and the caterpillars, unlike other species of caterpillar which can often be seen on walls, fences, various trees and bushes along with other structures, is generally only found on oak trees.

Although, having said that, when large populations completely defoliate oak trees in their local vicinity they will start feeding on other trees when running out of oak foliage to eat and they have now been seen on birch, beech, hazel, hornbeam and sweet chestnut trees.

It is important if you have oak trees in your garden, particularly if living in or near the infected areas of Richmond, Wandsworth, Hounslow, Ealing and Brent, that you keep an eye on your tree/s for signs of the caterpillars and their nests which can be spotted on trunks and branches.   Any nests you may see in the leaves almost certainly do not belong to the oak processionary moth but will be those of another species of harmless moth.

Should you be unfortunate enough to spot any oak processionary moth caterpillars or their nests in your oak trees, then keep yourself, other people, children, pets and livestock away from the infected tree or trees and do not be tempted to try and remove them or any nests yourself.

Report your sighting of these caterpillars to your local council, who may also advise that you should report your sighting to the forestry commission.  The councils of all infected areas, along with the forestry commission are all working very hard to keep the oak processionary moth under control.

Your local council may also be able to provide you with telephone numbers of suitable pest control operators that can remove the nests for you or contact a local, fully qualified and reputable tree surgeon, as many now also offer an oak processionary moth nest removal service.


Article Source: http://www.graftingardeners.co.uk/oak-processionary-moth/

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