Oak Processionary Moth

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Gristwood and Toms are the UK leading provider of OPM control services and we have developed ground breaking ways to treat and restrict its spread. We have a team on quick response to deal with nests as they are spotted. If you have any concerns that the Oak Processionary Moth might be affecting the trees in your area, then now is the time to act. The earlier they are spotted, the better chance there is of containment. Contact Gristwood & Toms for immediate help and advice

What is Oak Processionary Moth?

The Oak Processionary Moth (OPM) is a major defoliator of oak in Europe. The larvae (caterpillars) feed on the foliage of many species of oaks, including English, Sessile and Turkey oaks (Quercus robur, Q.petraea and Q.cerris). Hornbeam, Hazel, Beech, Sweet Chestnut and Birch are also reported to be attacked, although mainly when growing next to severely defoliated oaks.

Screen Shot 2014-09-10 at 14.07.25Oak Processionary Moth is also a risk to human health. The larvae (caterpillars) are covered in irritating hairs that contain a toxin and contact with these hairs, or their inhalation, can result in skin irritation and allergic reactions. These problems are significant because the Oak Processionary Moth is often most abundant on urban trees, along forest edges and in amenity woodlands.

Oak Processionary Moth is a native species of central and southern Europe, where it is widely distributed, but its range has been expanding northwards, presumably in response to climate change. It is now firmly established in northern France and the Netherlands, and has been reported in southern Sweden. Since 2006, OPM has been found in at least 11 London Boroughs, Surrey and Berkshire. It has spread radially from the 2 initial infestation locations in West London

OPM was first discovered in the UK in Richmond in 2006. A high incidence of rash amongst residents on housing estates led to an investigation by Environmental Health Services. A second site was identified on Hanger Lane near the A40, where imported oak trees had been planted at around the same time.

Health Risks

Risks To:

  • Skin – causing irritating rash.
  • Eyes – irritation and reddening of eyes.
  • Upper respiratory tract – causing sore throats and occasionally breathing difficulty Symptoms include vomiting, dizziness, fever, constant itching and general malaise.

It is a danger to humans, pets and livestock (particularly dogs and horses who tend to sniff or chew grass around the base of trees where toxic hairs have fallen).

Health Issues

  • Each caterpillar or larvae has approximately 700,000 toxic hairs from L4 stage (see life-cycle section).
  • The urticating (stinging) hairs can remain active in the environment for  over five years.
  • The urticating hairs and the shed skins can stay in a tree for years.
  • The urticating hairs spread by wind and tree or branch removal work

How Health Problems Arise

  • Problems arise through direct contact with nests or larvae and through indirect contact with urticating (stinging) hairs in the air.
  • From May through to July the urticating hairs swarm in the air in the areas around the larvae.
  • From May until August the urticating hairs drift in the wind from the nests. They can spread quite a distance over a short period as they become airborne.
  • The hairs are invisible to the human eye. They will get caught on skin and on any fabric and become very difficult to wash off. Therefore they will stay on clothing, canvass and laundry left on washing lines to dry.

Risk Groups

Tree workers and inspectors are at risk all year round from contact with old nests. Others who climb trees or sit at the base of the trees between May and August (when hairs fall to the ground) are also at high risk.

All those who use public outdoor spaces near to where trees are infected are at risk, including joggers, sportspeople, hikers and ramblers, dog walkers and so on.

Pets, especially dogs and horses are also at risk.

How it could affect Public lifestyle

OPM is relatively new to this country and outbreaks have not reached epidemic proportions. However in parts of Europe, where OPM is a major problem, communities have been severely disrupted. Based on what has happened elsewhere it’s possible that parks and play areas will need to be closed, sporting and community events cancelled and pet owners advised to keep their pets on leads or indoors.

Children may be advised to stay indoors and it may be necessary to keep doors and windows shut during the summer months. We need to do all we can to contain the spread and minimise the disruption to day to day life and that is why it is essential that any outbreak is detected at the earliest possible stage.