Cytospora canker

Cytospora canker is a serious fungal disease caused by various species of the Cytosporaceae family. It primarily acts as a wound parasite, invading the bark of weakened trees. This disease causes localized necrosis of the inner bark and cambium, eventually girdling branches or entire trunks.

The host range for this pathogen is extensive, encompassing a wide variety of deciduous trees. Fruit trees such as apples, pears, cherries, and plums are highly susceptible. Furthermore, it causes significant economic damage to poplar, willow, and mountain ash populations in forest nurseries and urban plantings.

The primary symptom is the formation of cankers, which appear as depressed, discolored areas on the bark. As the disease progresses, the bark becomes brittle and may crack, while the underlying wood often shows reddish-brown staining. In humid conditions, small pimple-like structures, known as pycnidia, erupt through the bark surface and release spores.

Environmental stress is a critical factor for the development and spread of Cytospora. Factors like drought, frost damage, sunscald, and improper pruning facilitate the entry of the fungus. The pathogen is disseminated by splashing rain and contaminated pruning tools, making it particularly difficult to manage in neglected or high-density orchards.

Control strategies emphasize prevention and rigorous sanitation.

• Remove and destroy all infected branches, cutting well into healthy wood.
• Disinfect pruning shears regularly to prevent pathogen transmission between trees.
• Maintain tree vigor through proper fertilization, irrigation, and avoiding physical damage to the trunk.
• Protect trees from sunscald and winter injury using light-colored trunk wraps or reflective paint.