Larch canker fungus

Lachnellula pseudofarinacea is a pathogenic fungus that causes necrosis of the bark and cambium in coniferous trees. As a member of the genus Lachnellula, it is recognized as a causative agent of canker diseases, which specifically impact the structural integrity and health of trees by impeding the transport of nutrients and water.

The primary host for this fungus is the Larch (Larix) species. The pathogen typically establishes itself in trees that have sustained mechanical damage, frost cracks, or insect wounds. Once the fungus enters the inner bark, it begins to proliferate, gradually killing the surrounding healthy tissue and creating lesions that grow year after year.

Visible symptoms include sunken patches on the bark that often become fissured as the tree attempts to callus over the infection. The hallmark of this disease is the presence of small, saucer-shaped apothecia, which appear on the surface of the cankers. These fruiting bodies are often covered in white, fuzzy hairs, giving them a distinct appearance during humid weather conditions.

The spread of Lachnellula pseudofarinacea is highly dependent on environmental factors, particularly high humidity and moderate temperatures. Spores are dispersed through the air and splashing water. Dense forest stands or crowded nursery settings with poor airflow provide perfect conditions for the pathogen to thrive and jump between individual trees.

The economic and ecological impact involves the stunted growth, deformity, and eventual mortality of the affected branches or stems. Management focuses on rigorous sanitation and prevention. This includes the removal and burning of infected branches, disinfecting pruning tools to prevent cross-contamination, and maintaining healthy tree vigor through proper site selection and spacing to ensure adequate light and air circulation.