Bulbous honey fungus

Pathogen and disease type. Armillaria cepistipes is a basidiomycete fungus responsible for white rot of roots and the base of tree trunks. It belongs to the genus Armillaria and acts as a facultative parasite, meaning it can survive both on living host tissue and dead organic matter. It plays a significant role in forest ecology by recycling woody debris, though it can become problematic in managed stands.

Host plants. The fungus has a broad host range, primarily infecting deciduous species such as birch, beech, and oak, though it can occasionally affect conifers. It typically colonizes trees that are already stressed due to environmental factors like drought, soil compaction, or previous damage by insects and other pathogens.

Symptoms and signs. The most visible sign of infection is the presence of yellow-brown mushrooms (fruiting bodies) clustered at the base of the tree during the autumn. Beneath the bark, dense white mycelial fans are found, and black root-like strands called rhizomorphs spread through the soil. The wood at the base of the trunk shows signs of bleached, stringy white rot.

Development and impact. The pathogen spreads through mycelial rhizomorphs in the soil, which bridge the gap between infected and healthy tree roots. Environmental conditions such as high humidity and moist soil favor the growth of Armillaria cepistipes. The economic and biological impact includes stunted growth, increased susceptibility to windthrow, and the gradual mortality of infected trees over several years.

Protection and prevention measures. Management strategies focus on silvicultural practices rather than chemical fungicides. Key actions include:

• Removing infected trees and stumps to reduce inoculum load in the soil.
• Ensuring proper forest hygiene to prevent the spread of rhizomorphs.
• Promoting healthy tree growth through appropriate stand thinning.
• Avoiding damage to tree roots during forestry operations to minimize infection entry points.