Neonectria obtusispora

Neonectria obtusispora is a pathogenic fungus belonging to the Ascomycota division, recognized as a significant agent of canker diseases in various woody plants. Unlike some more aggressive species in the genus, this pathogen often exploits wounds and natural openings in the bark to establish its mycelial colony within the host's conductive tissues.

The host range of this fungus includes a variety of hardwood species, most notably beech, maple, and birch. It tends to colonize trees that are already suffering from environmental stress, such as frost cracks, sunscald, or improper pruning wounds, turning minor injuries into persistent, damaging canker sores that disrupt nutrient flow.

The primary symptom of infection is the development of sunken, necrotic lesions on the trunk or branches. As the tree attempts to wall off the infection, a prominent callus ridge often forms around the margin of the canker, resulting in a distorted, lumpy appearance. During humid conditions, the fungus produces clusters of small, bright red perithecia on the affected bark surface.

Environmental conditions play a decisive role in the disease cycle, as the fungus relies on high atmospheric moisture for the dispersal of its ascospores and conidia. These spores are easily spread by wind and splashing water, making rainy spring and autumn seasons periods of high infection risk. The fungus can persist in the bark throughout the year.

Effective management requires a proactive approach centered on sanitation and wound care. Removing infected branches and debris is critical to reduce the spore load in the immediate environment. Protective treatments, including the application of copper-based fungicides to pruning wounds and maintaining tree vigor through proper fertilization, remain the most effective preventive measures.

• Regular inspection of bark for sunken lesions.
• Disinfection of pruning tools between trees.
• Application of wound sealants to prevent pathogen entry.
• Sanitary removal and disposal of infected wood.