Ash dieback

Ash dieback

© M J Richardson

A fatal fungal disease of ash trees

First confirmed in the UK in 2012, ash dieback, also known as 'Chalara' or Chalara ash dieback, is a disease of ash trees caused by a fungus called Hymenoscyphus fraxineus.

Ash dieback has already caused the widespread loss of ash trees in continental Europe and is now affecting countless woodlands, parks and gardens across the U.K, including several of our reserves.

Ash dieback symptoms

The main symptoms of ash dieback are:

  • Blackening of leaves which often hang on the tree
  • Discoloured stems, often with a diamond-shape lesion
  • Black and shrivelled shoots
  • The death of twigs and branches in the crown of mature trees
  • Small white fruiting fungal bodies on blackened stalks in early autumn

The disease causes ash trees to die
Young ash trees die quickly, whilst mature trees can be killed by a yearly cycle of repeated infection. Diseased trees may also get honey fungus, causing branches or whole trees to collapse.

Identifying ash dieback

Learn how to spot the tell-tale signs of ash dieback in the following video from the Forestry Commission.

More information about ash dieback

© Forestry Commission