The tree disease, Chalara fraxinea, emerged in Eastern Europe 20 years ago, and experts say it could change the British landscape in a way not seen since the height of the Dutch elm disease in the 1970s and 1980s.
Tens of millions of elm trees were killed or destroyed during the period.
Ash trees have covered Britain since the last ice age and can live for up to 400 years.
They are a key element of the ecosystem, providing homes and food for birds and other species.
Some say saving the ash is already a lost cause while others advocate selective felling and chemical applications as a last-ditch effort to save the iconic trees.
A nursery forced to destroy 50,000 ash trees after the disease was found in its stock announced on Monday that it may take legal action against the government for failing to block imports of potentially infected trees.
Photo: Woodland Trust