Giant polypore

The Giant polypore (Meripilus giganteus) is a significant wood-decay fungus responsible for causing white rot in the roots and base of tree trunks. It is primarily a saprotroph that can act as an opportunistic pathogen, compromising the structural integrity of the tree by degrading the wood tissues deep underground.

This fungus typically targets broad-leaved trees, including species like oak, beech, sycamore, and maple. Infection usually occurs through existing wounds in the root system or the root collar, often resulting from construction activities, soil compaction, or natural environmental stressors that weaken the tree's defensive mechanisms.

Symptoms often appear as gradual crown thinning, premature leaf fall, and a general decline in the tree's health. The most diagnostic sign, however, is the appearance of large, tiered, rosette-shaped fruiting bodies at the base of the tree or emerging from nearby roots during the late summer and autumn months, characterized by a brownish, fibrous texture.

Conditions favoring the spread of the fungus include moist, shaded environments and compacted, poorly drained soils. The spores are dispersed by air currents and water runoff, allowing the pathogen to colonize new hosts through root grafts or soil contact, particularly when the host tree's natural resistance is compromised by climate stress.

The pathogenicity of this fungus is hazardous because it destroys roots without showing outward signs until the tree becomes unstable. To manage and prevent the spread of the disease, consider these essential practices:

• Regular visual inspections of tree bases for fungal growth, especially after rainfall.
• Avoiding trenching or soil disturbances near established trees to protect roots.
• Improving soil drainage and aeration to reduce conditions favorable to fungal development.
• Removing and destroying infected fruiting bodies to limit local spore dispersal.