Cryptosporiopsis coryli

Cryptosporiopsis coryli is a pathogenic fungus known to cause significant bark damage in hazel trees (Corylus species). It belongs to the group of fungi that thrive by colonizing the cortical tissues of woody plants, causing localized necrosis that disrupts the vascular system and nutrient transport.

The primary host for this disease is the common hazel and various cultivated hazelnut varieties. While often considered a secondary pathogen that exploits plant stress, it can act aggressively in orchards where the trees are already compromised by environmental factors or poor horticultural maintenance.

Symptoms of the infection typically include the appearance of sunken, darkened lesions on the bark of twigs and branches. As the pathogen develops, these lesions enlarge, leading to cracks in the bark and the formation of pycnidia, which are small fruiting bodies of the fungus. Foliage above the affected area often shows signs of wilting or chlorosis.

The development of the disease is heavily favored by cool, wet weather, which promotes the release and dispersal of fungal spores. Rain splashes and wind serve as the primary transmission vectors, carrying the inoculum onto fresh pruning cuts, frost cracks, or sites damaged by insects, where the fungus gains entry into the plant host.

Management and prevention focus on maintaining tree vigor and strict sanitation. Essential practices include:

• Regular pruning of infected branches well below the necrotic area.
• Sterilizing pruning equipment to prevent mechanical spread.
• Applying copper-based fungicidal sprays during dormant seasons.
• Protecting tree trunks from sunscald and frost damage to minimize entry points.

Effective control requires persistent monitoring throughout the growing season. By reducing the volume of fungal inoculum in the orchard environment and ensuring that trees are not subjected to undue physiological stress, growers can successfully manage the impact of this pathogen and maintain healthy hazelnut production.