Cytospora canker is a fungal disease that primarily affects trees, particularly willows, poplars, and fruit trees. It is caused by the fungus Cytospora, which invades the bark and cambium layer, leading to dieback and cankers on the branches. Symptoms include sunken, discolored areas on the bark, and the tree may exhibit wilting or yellowing leaves. The disease often occurs in stressed trees, making them more susceptible to infection. Management strategies include proper tree care, such as watering and pruning, to reduce stress. In severe cases, affected branches may need to be removed to prevent the spread of the fungus.