Leucostoma canker

Leucostoma auerswaldii is a necrotrophic fungal pathogen belonging to the Ascomycota phylum. It is widely recognized as the causative agent of perennial canker and dieback in various woody hosts, particularly within the Rosaceae family, causing significant economic damage to orchard production.

The disease primarily affects stone fruits such as apricots, peaches, cherries, and plums, as well as several pome fruits. The pathogen targets the vascular tissues and bark, leading to sunken necrotic lesions, which eventually girdle the branches or stems, causing wilting and death of the distal parts of the tree.

The life cycle of this fungus involves the production of both conidia and ascospores throughout the growing season. Infection typically occurs via natural openings, winter injury, sunscald, or pruning wounds. Once established, the mycelium colonizes the cambium, producing pycnidia that break through the epidermis as distinct black bumps.

Environmental conditions such as high humidity, cool temperatures, and physical stress (drought or winter cold) significantly favor the spread and severity of Leucostoma auerswaldii. Weakened trees lack the energy to form a proper callus, allowing the fungus to progress rapidly through the bark and sapwood.

Integrated pest management strategies to control the infection include:

• Strict sanitation by removing and burning infected limbs and debris.
• Ensuring proper pruning practices, avoiding flush cuts and pruning during rainy weather.
• Applying wound dressings to protect entry points from fungal spores.
• Maintaining tree vigor through appropriate fertilization and water management.
• Using copper-based fungicides to reduce the inoculum load on the tree surface.