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Ash dieback disease

Ash dieback disease, also known as Chalara fraxinea, can be a serious threat to ash trees across the UK.

Advice on preventing or reporting the disease

There is no need to fell ash trees unless Chalara is confirmed in the tree, and the precautionary felling of trees is not recommended at this time.

Only purchase trees from reputable suppliers and make sure that they are certified disease free stock.

The disease does not give any exemptions from legal requirements to seek permission to do works to protected trees, and to give notice of any works to trees in conservation areas. If you need advice on whether your tree is protected please contact your local council's tree protection department.

If you're concerned by a possible case, you should:

  1. Approach the owner of the tree concerned.
  2. Contact the government helpline on 03459 335577.

Frequently asked questions


What is ash dieback?

Ash dieback is caused by a fungal organism called Chalara fraxinea. The disease causes leaf loss and crown dieback in affected trees, and can lead to tree death. The fungal disease is carried on the wind and by transportation of infected trees.

Which ash trees are at risk?

All ash trees are vulnerable; it is not known to spread to any other type of tree. It is particularly destructive to young trees. Older trees can survive initial attacks, but tend to succumb eventually after several seasons of infection

The disease does not cause rapid or catastrophic failure of trees. Any danger from dead or dying trees is likely to be gradual and obvious over a period of year. Chalara fraxinea is not fatal to all ash trees. The older infected trees may be able to survive indefinitely, although may be at increased risk of other infections

For more information, visit the  Forestry Commission - Chalara website.

How serious is ash dieback?

The disease is a potentially serious threat to ash trees across the UK.

Ash dieback is a new disease affecting ash trees (Fraxinus sp.) and has recently been found in Britain.

The disease has already caused extensive loss of ash trees in mainland Europe, and could be a major threat to wild and planted ash in the UK if it takes hold here.
Chalara dieback of ash, caused by the fungus Chalara fraxinea, was found in the UK for the first time in early 2012 in young ash plants in tree nurseries and recently planted sites, including a car park, a college campus, and a new woodland.

The disease has not yet been found in the South West.

There is a government ban on the import of ash plants into the UK and on the movement of ash plants, seeds and trees into and around the UK. The ban does not extend to the movement of ash timber or firewood except from sites where the disease has already been found.

What are the signs of the disease?

The disease is is not always easy to identify so check  Forestry Commission for videos and guides which explain the symptoms and identification of the disease.

It is characterised by the premature loss of leaves from the outer parts of the crown (top and sides), accompanied by long diamond-shaped lesions or areas of sunken and discoloured bark on twigs.

These lesions girdle twigs and small branches, starving the leaves above of water and nutrients and causing whole branches to die. In mature trees, it is the new growth that is affected.

You can get more information on the Food and Environment Research Agencys (FERA) video which shows how to identify ash dieback disease.

Se also the  guide to the symptoms of Chalara.

Because one of the symptoms of Chalara fraxinea is leaf loss, identification of the disease will be difficult in the autumn when the trees are losing their leaves.

What should I do if I think I have found Chalara disease?

The disease has been classified as 'notifiable' by DEFRA, which means that any suspected cases of the disease must be reported to the appropriate plant health authorities.

If you think that you have identified Chalara fraxinea on an ash tree, then you should contact one of the following bodies:

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