Ash Dieback is a serious tree disease caused by the fungus Hymenoscyphus fraxineus. It primarily affects ash trees, leading to leaf loss, crown dieback, and eventually tree death. The disease spreads through spores and can be transmitted by wind, rain, or contaminated equipment. First identified in Europe in the early 1990s, Ash Dieback has since spread to many countries, including the United Kingdom. Efforts to manage the disease include monitoring affected areas and promoting the planting of resistant tree species to help preserve biodiversity in forests and woodlands.