Ash Dieback (Chalara)


Chalara fraxinea, known as ash dieback disease, is a relatively newly described fungal disease of ash which was first named in 2006 although dieback symptoms in ash had been first noted in Poland in the early 1990s. The harmful reproducing stage of the fungus, a new species Hymenoscyphus pseudoalbidus, was later discovered in 2010. The disease has spread rapidly across much of Europe, with the majority of European countries where ash is present now reporting the disease.

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. Death of the trees can occur, with younger trees (less than 10 years old) succumbing more rapidly.

It is likely that plants for planting that are imported from other European countries are the highest risk pathway for spread into Ireland. Wood, including firewood, is also likely to be a pathway.


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.)

For more on symptoms see the Information Note on Chalara fraxinea ash dieback disease, below.


On 12th October 2012, the Department confirmed Ireland’s first case of Chalara fraxinea infection in a young forestry plantation in County Leitrim which had been planted with imported trees. The trees on this site and on all ten other sites planted with the same batch of trees were subsequently destroyed under Department supervision. Following this first finding, the Department has undertaken a major survey of ash. The table below describes the current situation regarding confirmed findings. The Department continues to survey for this disease in forestry plantations, nurseries, roadsides, farms, etc.


Chalara fraxinea is not a regulated disease under the EU Plant Health Directive (Council Directive 2000/29/EC).

A Ministerial Order was introduced on the 6th November 2012 to restrict the movement of ash plants and seed into Ireland. The provisions also include restrictions on ash wood imports. A copy of the legislation, S.I. 431 of 2012 is provided below. This order provides for measures to prevent the spread of Chalara fraxinea in the genus Fraxinus L. Similar legislation was introduced in Northern Ireland at the same time.


Forest owners, forest nursery staff and members of the public are asked to be vigilant for the disease and report (with photographs, if possible) any sites where there are concerns about unusual ill health in ash, to the Forest Service, Department of Agriculture, Food & the Marine, by e-mail or by phoning 01-607 2651. Your report will be followed up by a Forestry Inspector.

In addition, nursery stock producers should direct queries to your local Plant Health Inspector immediately. Alternatively, queries can be sent by e-mail to, by fax to 01-627 5994, or by contacting the Department’s Offices on 01-505 8885.