Chalara Dieback of Ash (Chalara fraxinea)

Ash dieback photo courtesy Andrej Kunca, National Forest Centre – Slovakia,

Chalara fraxinea is being treated as a quarantine pest under UK national emergency measures; it is important to report any suspected cases.

The disease caused by the Chalara fraxinea fungus results in leaf loss and crown dieback in ash trees, which can lead to tree death in affected trees. Ash trees suffering with symptoms from Chalara fraxinea are increasingly being found across Europe and now have been confirmed at sites in the UK.

Chalara fraxinea Symptoms
Chalara fraxinea can be visible on leaves, shoots and branches of affected trees. In severe cases, the entire crown can show leaf loss and dieback, epicormic shoots can also form on the branches and trunk.

The Foliage
Leaves can suffer from wilting and a black-brownish discolouration can occur at the leaf base and midrib. Dieback of shoots and twigs is also very characteristic.

Branches and Stems
Small lesions or spots appear on the bark of the stems and branches and enlarge to form cankers. This can cause wilting and dieback of shoots and branches in the upper crown.

The Tree
Trees with withered tops and shoots are very typical. Heavily affected trees will have extensive shoot, twig and branch dieback and often have extensive epicormic shoots. Chalara fraxinea has also been isolated from the roots of symptomatic trees, as well as from leaves, shoots and branch/stem lesions.

How the disease spreads
How Chalara fraxinea spreads is uncertain, but local spread may be caused via rain splash or insects. Over longer distances the risk of disease spread is most likely to be via the movement of diseased ash plants. Movement of logs or unsawn wood from infected trees may also be a pathway for the disease.

Bartlett Tree Experts in the News
Bartlett staff are often interviewed on topics concerning plant health. Below are links to interviews and reports about Chalara dieback of ash in which Bartlett’s experts were involved.

ITV: Deadly ash tree disease spreads across the UK

BBC Radio 4: Ash dieback ‘beyond containment’

The Telegraph: Ash dieback now beyond containment

If you have ash trees on your property, contact Bartlett to have an arborist come to your property and inspect your trees. In the UK, call 0845-600-9000 or make an appointment online.

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