The disease caused by the fungus Chalara fraxinea causes leaf loss and crown dieback in affected trees, and it can lead to tree death. It is a significant threat to one of our widespread native trees. Ash is the third most common broadleaf native tree species in Great Britain after oak and birch and is the predominant tree species in approximately 129,000 hectares of woodland in Britain.
The fungus has caused widespread damage to ash tree populations in continental Europe and has the potential to kill millions of ash trees if it becomes widely established in Great Britain. The spread of this disease would pose a serious threat to associated biodiversity, including bats, and measures to prevent its spread are imperative. However, the potential for large-scale destruction of mature ash trees has raised concerns about the impact on roosting bats.