In 2013, the ash dieback became widely apparent, with trees suffering from a disease. Chalara dieback of ash is a serious disease of ash trees caused by a fungus called Chalara fraxinea, including its sexual stage, Hymenoscyphus pseudoalbidus. The disease causes leaf loss and crown dieback in affected trees, and usually leads to tree death. This issue is still trying to be contained but continues to cause problems to this day, and ash tree populations are dwindling due to the severity of the problem.