Diseases

New Ash tree disease arrives in Britain

Over the last few years I have written articles on diseases affecting Oak trees and Horse Chestnut trees, we now need to add Ash trees to this list.

Damage to the trunk

The disease is caused by a fungus called Chalara fraxinea which has been tracked across Europe from Denmark through Germany, France and the Netherlands. The disease has wiped out 90% of the Ash trees in Denmark in just 7 years. When we consider that these trees make up around 30% of our native species it could have a real impact in the UK similar to the devastation caused by Dutch elm disease to Elm trees in the 1970’s.

The disease was first detected in tree nurseries from imported Ash trees arriving from EU countries. A ban on imports is now in place but it may be a little too late as the disease has been identified in Norfolk and Suffolk including on a wildlife trust site.

The disease has a number of symptoms for you to watch out for:

Damage to the stem
  1. Leaves wilt and turn a black brown colour
  2. Twigs and shoots dieback
  3. On the branches and trunk lens shaped lumps and black spots appear
  4. The upper crown of the tree starts to die back
  5. The tree develops growth on the lower braches to try and survive (epicormic growth)

There is uncertainty of how Chalara spreads from the obvious transmission via imports in nurseries to longer distance transmission via spores in the wind, insects and movement of infected timber.

Damage to the foliage

We must hope that the belated restrictions in place and increasing public awareness of the problem will mean that suspected cases are dealt with quickly. If you think your garden ash tree may be infected we advise a qualified arborist is contacted and if the disease is confirmed it is reported to the Forest Research Disease Diagnostic Advisory Service.