Chalara Dieback of Ash

Chalara ash dieback, often called ‘chalara’ or ‘ash dieback’, is a fungal disease affecting ash trees of all ages across Europe and some parts of Asia. 

The disease was first recorded in the UK in 2012 and has since spread to most of the country. The widespread prevalence of this disease has led to significant losses of our ash trees, transforming UK landscapes and jeopardizing numerous species that depend on them.   

A characteristic symptom of this disease is the presence of diamond-shaped lesions on the branches and stem of the tree; these tend form around the point that a shoot or branch joins the trunk. Other symptoms include wilting of leaves and shoots and dieback of branches. Later in the season, the small, white, cup-shaped fruiting bodies of the fungus can be seen in the leaf litter around the base of the tree. The fungus grows inside the tree, blocking the essential water and nutrient transport systems, which is often fatal.  

For more information on Chalara dieback of ash, see the resources below.