Apple canker is a disease that affects apple trees, causing damage to the bark and branches, which leads to reduced fruit production and lower quality of the apples. There are a number of different synonyms for apple canker, including bacterial canker, apple scab, and black rot. These diseases are caused by different pathogens, but all result in similar symptoms, including dark spots on the leaves and fruit, necrotic tissue on the branches and trunk, and reduced tree vigor. Careful monitoring and management can help prevent the spread of these diseases and maintain healthy apple trees that can produce high-quality fruit for many years to come.