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Ash Dieback Disease

A new disease affecting Ash trees has recently been found in Britain. The disease has already caused large losses of Ash trees in mainland Europe, and could be a major threat to Ash trees in the UK.

If you think that you have identified ash dieback disease on an Ash tree, then you should contact the Forestry Commission.

Report Ash Dieback Disease to the Forestry Commission online

What causes ash dieback disease?

Ash dieback disease is caused by the fungus Chalara fraxinea. It was found in the UK for the first time in 2012 in young Ash plants in tree nurseries and recently planted sites.

The disease is characterised by the premature loss of leaves from the outer parts of the crown (top and sides). It is 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.

What is being done about the disease?

The government has implemented a ban on the import of Ash plants into the UK. There is also a ban 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.

Government bans imports of Ash trees (DEFRA)

What are the signs of the disease?

The Forestry Commission have produced the following video showing how to identify the disease.

View further information on Chalara, produced by Forestry Research.

Because one of the symptoms of Chalara fraxinea is leaf loss, identifying the disease will be difficult in Autumn when trees naturally lose their leaves.