Chalara ash dieback : Observatree guides

Ash dieback is caused by the fungus Hymenoscyphus fraxineus and is commonly
referred to as Chalara ash dieback. Once a tree is infected the disease is usually
fatal. The disease can kill a tree host directly through the actions of the pathogen, or
indirectly by weakening it to the point where it succumbs more readily to attacks by
other pests or pathogens. Ash dieback only affects ash trees (Fraxinus spp.) and ash
trees of all ages can be affected.