Lachnellula

Lachnellula is a genus of ascomycete fungi responsible for severe necrotic diseases in conifers, most notably known as larch canker. The primary pathogen, Lachnellula willkommii, attacks the bark and cambium of trees, causing structural damage that hinders the transport of water and nutrients throughout the tree's vascular system.

This fungus predominantly affects larch species (Larix), although it can be found on other coniferous genera under favorable conditions. It is a major concern in both forestry, where it impacts timber quality, and horticulture, where it threatens the aesthetic value and survival of ornamental evergreen plantings.

The disease is characterized by the development of depressed lesions and deep cankers on branches and stems. The most diagnostic sign is the presence of small, bright orange, cup-shaped apothecia (fruiting bodies) clustered along the margins of the cankers. In response to the infection, trees often exhibit heavy resin flow, and girdled stems eventually die above the site of infection.

Environmental conditions play a crucial role in disease epidemiology. High humidity, mild temperatures, and frequent rainfall facilitate spore dispersal and infection. Frost damage, mechanical injuries, and insect wounds create entry points for the pathogen, making weakened trees particularly susceptible to colonization.

Management and prevention strategies focus on maintaining tree vigor and reducing inoculum pressure. Key practices include:

• Pruning and destroying infected branches to limit spore spread.
• Removing severely cankered trees from the stand to eliminate infection sources.
• Ensuring proper spacing and airflow in plantations to prevent moisture accumulation.
• Monitoring nursery stock for early signs of infection during damp seasons.