Ash tree affected by ash dieback disease

A common ash tree (Fraxinus excelsior) in Ashwellthorpe Wood, Norfolk, UK, May 2017. The picture shows a mature ash tree shortly after leaf break. The tree shows severe symptoms of ash dieback infection, a disease caused by the fungus Hymenoscyphus pseudoalbidus (formerly Chalara fraxinea). The upper branches have died, and in many cases fallen, leaving the tree with little remaining of its former spreading crown. Such leaves as are visible occur on scattered small still living side branches lower down. This tree is dying. Smaller trees in the background are as yet showing fewer symptoms. Ash dieback was first noticed in the UK in 2012 at Ashwellthorpe Wood. This picture illustrates the extent of damage that has been caused over a period of 5 years. The current outbreak of the disease is expected to kill the majority of UK ash trees.