What is it?
Chalara dieback of ash is a fungal pathogen which attacks the leaves of ash trees, causing an infection which spreads from the leaf through the shoots and twigs and into the tree, causing lesions and tissue death. As the infection spreads through the tree, it may cause dieback of the crown, eventually leading to tree death. The infection is spread by airborne fungal spores, released from fungi which grow on the leaf litter of ash trees, which land on the ash leaves. Once these spores have landed, they germinate and enter the leaf as an infection.