Ash Dieback Disease (Chalara Fraxinea)

Ash Dieback Disease was first identified in Poland in 1992. Since then it has spread across Europe with Norway, the Netherlands, Germany and Denmark particularly affected. In Denmark it is reported that some 90% of their Ash trees may have been killed or been infected by the fungus causing the disease.

In the UK evidence of the disease was found early in 2012 in tree nurseries and sites recently planted with young Ash trees. However it was not until October that the disease was found in established trees, in East Anglia. A recent survey has now revealed affected trees in Kent.

It is not yet fully understood how the disease is transmitted. Initially the disease was carried on young trees imported from Europe and these infected new planting sites. It is now thought likely that spores of the fungus have also been carried by winds blowing from Europe, infecting established trees and woodlands.

The presence of the disease does not make an infected tree any more hazardous or likely to fail. It can take a number of years to kill a mature tree and there is evidence of a natural resistance amongst the Ash population. It is therefore premature to consider felling trees. It will be difficult over the winter months to assess whether trees have been infected as the most obvious visible symptoms affect the leaves.

Additional information, including guidance on how to identify the disease and how to formally report suspected outbreaks is available on the Forestry Commission website.

Details of new restrictions on the importation and movement of Ash trees (including seeds and seedlings) can be found on this page of the forestry commssions website.

The Forestry Commission have just published a new Chalara helpline, which can be used to report suspected cases of Chalara fraxinea infection.

Chalara helpline: 08459 33 55 77 (open 8am – 6pm every day)


To report any suspected cases of Chalara please complete the form on the Forestry Commission website and include photographs.

Updated: 19th December 2012