Lachnum fasciculare

Lachnum fasciculare is a fungal species belonging to the order Helotiales, known primarily for its presence on decaying wood. While often classified as a saprotroph, it frequently behaves as a weak parasite, colonizing stressed, injured, or diseased woody plants and contributing to the degradation of their structural integrity.

The causative agent forms distinctive fruiting bodies known as apothecia, which appear as small, cup-shaped structures covered with fine hairs. These structures are typically bright yellow or cream-colored and are characterized by their habit of growing in dense clusters, which is a key diagnostic feature for field identification.

The fungus affects a variety of broad-leaved woody species, including birch, alder, and several orchard trees. The infection path typically involves open wounds, pruning cuts, or frost cracks, where the fungus gains access to the inner tissues of the plant, potentially leading to localized necrosis or decay if the tree's defense systems are compromised.

Development and spread are heavily dependent on climatic factors such as high atmospheric moisture and moderate temperatures. The spores are primarily dispersed by wind and splashing rainwater, landing on vulnerable, moist woody substrates where they germinate and establish new mycelial colonies, further weakening the host plant.

Effective management strategies focus on sanitation and structural care:

• proper disinfection of pruning tools and wounds using copper-based or systemic fungicides;
• maintaining plant vigor through balanced irrigation and nutrient management;
• removal and destruction of debris or dead wood where the fungus may sporulate;
• avoiding mechanical damage to the bark to prevent entry points for the pathogen.