Ash dieback and other pests and pathogens of fraxinus on the island of ireland

The common ash (Fraxinus excelsior) is one of the most important native tree species in Ireland but is threatened by the spread of ash dieback (also known as Chalara disease). The disease is caused by the fungal pathogen Hymenoscyphus fraxineus, which is decimating ash in Europe.The first part of this review summarises the scientific discoveries on H. fraxineus, focusing on its origin and infection cycle as well as its impact on Irish forestry. In addition to directly damaging ash, the action of H. fraxineus makes ash trees more vulnerable to attack by other opportunistic secondary pathogens, which accelerate their death. Ireland, as an island, has a natural barrier which slows the spread of pathogens compared to many other countries in the European mainland, but the threat of further pathogen introduction remains real and likely. The second part of this review focuses on the spread of other pathogens of ash, and on their incidence and importance in Ireland.