Diplodia canker

The disease is caused by the fungus Botryosphaeria stevensii (anamorph Diplodia seriata), a serious pathogen known for causing cankers and dieback in a wide range of woody plants. It primarily targets the bark tissues, leading to systemic decline of the tree.

Common hosts affected by this fungus include various fruit crops, most notably apple (Malus domestica) and pear (Pyrus communis). It can also infect other deciduous trees and shrubs, acting as a latent infection that manifests under stress.

Symptoms typically appear as sunken, dark, discolored areas on the branches or trunks. As the infection progresses, the bark may split, revealing the underlying woody tissue, and pycnidia (small black fruiting bodies) often appear on the surface of the dead bark.

The development of Diplodia canker is heavily favored by environmental stress factors such as drought, frost injury, or sunscald. The spores of the fungus are dispersed by rain splash and wind, entering the tree through wounds or pruning cuts, especially during periods of high humidity.

The damage caused by this disease is significant, as it can lead to complete branch death or tree collapse if the canker girdles the main stem. Control strategies focus on pruning out infected limbs, sterilizing tools between cuts, minimizing physical damage to the bark, and applying protective copper-based sprays during the dormant season.