Ash dieback

Ash dieback is caused by a fungus.

recognize ash dieback
Ash dieback, photo: Fera – Fera – OGL v1.0

Ash dieback is caused by the fungus Hymenoscyphus fraxineus. The fungus affects ash trees. The fungus lives off the tree’s wood, branches and leaves.
Hymenoscyphus fraxineus is an exotic species and is native to East Asia. Ash dieback was first spotted in Poland and Lithuania in 1990. By 2012, the fungus had spread over large parts of Europe, including the United Kingdom.
Hymenoscyphus fraxineus affects both old and young trees.
Not all ash trees are susceptible to this fungus: the Manna ash (Fraxinus ornus), the American ash (Fraxinus americana) and the Green ash (Fraxinus pennsylvanica) are less susceptible.

Where to find

  • Common ash (Fraxinus excelsior)
  • Narrow-leaved ash (Fraxinus angustifolia)
  • Black Ash (Fraxinus nigra)


Once affected by the fungus, ash dieback cannot be reversed. No fungicides or control methods have yet been found.


Since control is not possible, efforts are being made to grow resistant trees. It’s not that far yet.