Cytospora canker

Cytospora canker, caused by the fungus Cytospora ceratosperma, is a destructive bark disease that affects a wide range of fruit and ornamental trees. It is characterized by the development of necrotic lesions on branches and trunks, which disrupts the flow of nutrients and often leads to the death of the tree.

The disease primarily targets stone and pome fruits, including apples, pears, peaches, and cherries. Trees that are weak, stressed by drought, poor nutrition, or physical injuries are significantly more susceptible to infection by this opportunistic pathogen.

Symptoms typically include the formation of discolored, sunken areas on the bark. As the fungus colonizes the inner bark, small, pimple-like structures called pycnidia appear on the surface of the lesions. Infected branches often show premature wilting, foliage yellowing, and eventually, the entire branch may die back.

The development of the disease is highly dependent on environmental conditions, particularly moisture and temperature. Spores are released during wet weather and enter the tree through pruning wounds, sunscald cracks, or areas damaged by insects. Once inside, the fungus spreads rapidly, especially in poorly maintained orchards.

Effective management requires an integrated approach. The most critical step is the removal and destruction of all infected wood to reduce spore load. Key preventive strategies include:

• Avoiding unnecessary pruning during wet or humid weather conditions.
• Maintaining tree vigor through proper irrigation and fertilization.
• Protecting trunks from sunscald using white latex paint.
• Sterilizing pruning tools between cuts to prevent cross-contamination.