Ash dieback is not a native disease. It was imported into the country around 30 years ago. As our ash trees did not evolve with this disease, they have limited defences against it. The fungus that causes the disease lives in the woodland floor in infected areas and produces fruit from July to October. The fruits release spores that are carried through the air, causing further infection throughout the ash tree population.
Although trees can fight back and recover to some extent, repetitive infections will eventually kill.