Valsa canker

Valsa canker is a serious fungal disease caused by the pathogen Valsa ceratosperma, which primarily attacks the bark and cambium of woody plants. As a destructive necrotic disease, it progressively destroys the vascular system of the tree, often resulting in severe dieback and eventual death of the affected plant if left untreated.

The primary hosts for this pathogen are pome fruit trees, specifically the domestic apple (Malus domestica) and the common pear (Pyrus communis). The fungus frequently targets stressed trees, exploiting physiological weaknesses to colonize the host tissues and establish long-term infection sites within the orchard.

Symptoms initially appear as reddish-brown, slightly sunken lesions on the bark. As the disease advances, these areas become necrotic and dry out, often leading to deep cracking. During the reproductive stage, the fungus produces numerous tiny, pimple-like structures on the surface of the bark, which release spores that can spread to healthy parts of the tree or adjacent plants.

The development and spread of Valsa canker are highly dependent on environmental conditions, particularly high humidity and temperature fluctuations. The fungus enters the tree through physical wounds such as frost cracks, sunburn, or poorly healed pruning cuts. Once inside, the pathogen proliferates during periods of high moisture, utilizing rain splashes and wind for secondary dissemination.

Management strategies focus on a combination of cultural and sanitary practices to reduce disease pressure. Key protective measures include:

• Pruning and destroying infected branches to eliminate the inoculum source.
• Surgical removal of cankered bark down to healthy wood, followed by fungicide application.
• Protecting tree trunks from sunscald and frost damage to prevent entry points.
• Maintaining tree vigor through proper fertilization and irrigation to improve natural defense systems.