Populations of European ash trees, Fraxinus excelsior, are susceptible to a chronic tree disease called ash dieback. Since 2012, this disease has spread through Europe causing large-scale loss of woodland. • Ash dieback is caused by a fungal pathogen. • Symptoms include stem lesions, death of growing shoots and wilting of leaves. • To limit the spread of the disease, 693 hectares of ash woodland were cleared in the UK between 2012 and 2015. Clearing the woodland involved uprooting the trees and burying them. [Table 2.1] shows the numbers of new cases of ash dieback in a variety of different environments in the UK between 2013 and 2015.