NOTICE - The address of this website has changed. Please update your bookmarks.
Chalara (Hymenoscyphus fraxineus) - infections confirmed in the Wider Environment as at

What is Chalara?

Chalara dieback of ash is a serious disease of ash trees caused by a fungus which was previously called Chalara fraxinea, now known as Hymenoscyphus fraxineus. The disease causes leaf loss and crown dieback in affected trees, and is usually fatal.

What does the Viewer show?

The Chalara Viewer opposite shows England, Scotland and Wales and a grid of 10km squares ('hectads'). The shaded squares show areas where Chalara dieback has been confirmed to be affecting ash trees in the natural environment, and the colour of the square shows which year the first record in that area was made. You can zoom in/out and find a UK address or postcode using the controls on the map. Clicking on the map within a Grid Square will display information for that Grid Square in a pop-up window.

Where can I find out more?

For more information on Chalara dieback of ash please see the Chalara pages of the Forestry Commission Website

How do I report Chalara?

We would encourage all members of the public to report the disease in new (unshaded) areas. If you suspect you have found a new infection, please report it by using Tree Alert on the Forestry Commission website.


This web map is run by a Defra project team including Fera, Natural Resources Wales and Forestry Commission.

This responsive website has been designed to work with most modern browsers including IE7+, FireFox, Chrome and Safari.

If you experience problems viewing the map, please contact

Infected Square Opacity
  1. Less
  2. More