Cytospora canker

Cytospora canker, caused by the fungus Cytospora intermedia, is a destructive bark disease that affects a wide range of fruit trees. It is characterized by the formation of necrotic areas on the bark, leading to the dieback of branches and, if left unchecked, the death of the entire tree. This pathogen is particularly dangerous in commercial orchards due to its ability to spread rapidly under favorable environmental conditions.

The disease primarily targets stone and pome fruits, including apples, pears, peaches, and cherries. The fungus is a wound parasite, meaning it enters the tree through mechanical injuries, winter frost cracks, sunscald, or pruning wounds. Trees that are stressed due to drought, poor soil fertility, or extreme weather conditions are significantly more susceptible to infection by this fungus.

Clinical signs of infection typically include the development of darkened, sunken lesions on the bark. As the disease progresses, the bark may become cracked and pull away from the wood. Small, pin-like fungal fruiting bodies known as pycnidia appear on the surface of the infected areas. In humid weather, these structures release spores that can further infect healthy parts of the tree or neighboring plants.

The development of the disease is highly dependent on environmental factors, particularly moisture and temperature. High humidity facilitates the production and spread of spores, while warm spring and autumn temperatures allow the fungus to colonize wood tissue actively. Poor sanitation practices in the orchard, such as leaving diseased wood on the ground or failing to sanitize pruning tools, accelerate the spread of the pathogen.

Management and prevention require an integrated approach to maintain tree vigor and reduce inoculum levels:

• performing regular pruning to remove infected branches, cutting well into healthy tissue;
• sanitizing pruning equipment between cuts to prevent cross-contamination;
• protecting tree trunks from sunscald and frost damage using white paint or wraps;
• optimizing irrigation and fertilization to minimize tree stress;
• applying copper-based fungicides to protect open wounds and reduce the potential for spore germination.