Larch Canker

The causal agent of larch canker is the ascomycete fungus Lachnellula willkommii. This pathogen is a serious threat to larch plantations, causing necrotic lesions on the trunk and branches that significantly impede the development of the tree and reduce its economic value.

The primary hosts of this pathogen are species within the genus Larix, with European and Siberian larch being particularly susceptible. Younger trees are most vulnerable, and severe infections can result in permanent stem deformation, branch dieback, or even the death of the entire tree under extreme conditions.

Symptoms of the disease are characterized by sunken necrotic areas on the bark. As the fungus progresses, these areas form open wounds or cankers. The tree often attempts to wall off the infection, leading to the formation of callus tissue ridges. During humid weather, small orange or yellowish, cup-shaped fruiting bodies (apothecia) appear on the surface of the infected bark.

The disease thrives in environments with high humidity, frequent fog, and cool temperatures, which allow the fungal spores to germinate and spread efficiently. The pathogen usually enters the tree through cracks, wounds, or frost damage on the bark. Trees planted in frost-prone hollows or areas with poor air circulation are at a significantly higher risk of infestation.

Management of larch canker involves integrated forest health practices. Key strategies include the removal and destruction of severely infected trees to reduce the inoculum level, avoiding planting larch in high-risk frost pockets, and ensuring proper spacing to promote air movement. Monitoring young stands is critical for early detection and mitigation of potential outbreaks.

• Regular monitoring of plantation health.
• Sanitary removal of infected trees.
• Selection of resistant larch varieties for new plantings.
• Maintenance of good stand hygiene and ventilation.