Chalara dieback of ash trees (Chalara Fraxinea)

Chalara dieback is a disease caused by a fungus called Chalara fraxinea (C. fraxinea). It causes leaf loss, lesions on the bark and dieback of the crown of affected ash trees and may lead to the death of the tree. The disease is spread by spores from the fruiting bodies of the fungus on dead leaves.

Until recently, all cases of the disease were thought to be linked to imports of infected nursery stock used at tree planting sites. But signs have now been found in young and mature trees in the wider environment.

It is not yet clear what its current distribution is, or how it will affect our stock of native ash trees. Current indications are that, while generally fatal to younger trees, older trees may be more resistant or take longer to succumb.

On 29 October 2012 the UK government passed emergency legislation restricting imports into, and movements within, Great Britain of ash seeds, plants, and trees.

Monitoring the distribution of the disease and implementing measures to control it is the responsibility of Government agencies; the Food and Environment Research Agency (FERA) and the Forestry Commission.

Detailed information on the disease, symptoms and distribution can be found on the Forestry Commission - chalara (ash) dieback disease website. 

If you think you have spotted the disease please look at the pictorial symptoms guide on the Forestry Commission - chalara (ash) dieback disease website. 

In autumn and winter, native ash trees will naturally be shedding their leaves making it very difficult to identify the disease. There are also other causes of ash dieback, so it is important to distinguish them from Chalara.

Suspected cases should be reported  to the dedicated Forestry Commission Chalara Helpline which is open 8.00am - 6.00pm every day.