Giant polypore

The giant polypore (Meripilus giganteus) is a significant wood-decaying fungus that acts as a pathogen, causing white rot in the roots and buttress roots of various deciduous trees. By breaking down wood structures, it significantly compromises the structural integrity of the host, often leading to sudden tree failure.

It predominantly attacks broad-leaved tree species, including beech, oak, lime, and horse chestnut. While it is primarily a saprophyte, it exhibits strong parasitic tendencies, particularly on mature trees in garden settings, parks, and urban environments where the root systems are frequently subjected to stress or mechanical damage.

Key symptoms of an infestation include progressive crown dieback, sparse foliage, and chlorosis of leaves during the growing season. The most diagnostic sign is the presence of large, rosette-shaped fruiting bodies appearing at the base of the tree. These fruit bodies are initially fleshy and pale, but they turn dark brown or black upon touch or as they age.

The development and spread of the fungus are favored by moist soil conditions and the presence of open wounds on the tree's roots. Spores can enter the tree through damaged tissues, while mycelium can spread through soil contact between healthy and diseased roots, leading to a slow but lethal decay process within the tree's base.

Management of the giant polypore focuses on mitigation rather than chemical control, as effective fungicides for this pathogen in landscape settings are limited. Arborists should focus on assessing the tree's stability once the fungus is detected. Key practices include improving soil aeration, minimizing physical root disturbance, and removing severely compromised trees to prevent the potential risk of collapse.