Forest disease

Forest disease


What is Ash Dieback disease?

Chalara ash dieback disease is a relatively new serious disease of ash caused by fungal pathogen Chalara fraxinea. It has spread rapidly across much of Europe, with the majority of European countries where ash is present now reporting dieback. The organism has relatively recently been identified, but its origin remains uncertain and its biology is not yet fully understood. The disease is only known to be present in Europe.

What are the symptoms?

Common ash (Fraxinus excelsior) is susceptible to Chalara ash dieback disease as are a number of other species of ash. The disease can affect ash trees of any age and in any setting. Deaths can occur with younger trees (less than 10 years old) suffering mortality more rapidly, while the infection can be chronic in older trees. The wide range of symptoms associated with Chalara ash dieback disease includes:

The wide range of symptoms associated with Chalara ash dieback disease includes:

  • Necrotic lesions and cankers along the bark of branches or main stem
  • Foliage wilt
  • Foliage discolouration (brown / black discolouration at the base and midrib of leaves)
  • Dieback of shoots, twigs or main stem resulting in crown dieback
  • Epicormic branching or excessive side shoots along the main stem
  • Brown / orange discolouration of bark

Note: The symptoms described above are not exclusive to Chalara fraxinea and may be attributable to a number of other causal agents or factors, e.g. frost.


Teagasc Watch Our for Ash Dieback Graphic

What to do if you suspect your plantation has the disease?

Forest and land owners are asked to be vigilant for the disease and to report (with photographs, if possible) any sites where they have concerns about unusual ill health in ash, to the Forest Service, Department of Agriculture, Food and the Marine: by email (; or, by phone (01-607 2651).

Please do not remove any plant material from a site containing suspect trees.

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