Alder webcap

The Alder webcap (Cortinarius alnetorum) is a mycorrhizal fungus commonly found in association with alder trees. In the context of forestry and plant health, it is categorized as a beneficial symbiont rather than a plant disease, facilitating nutrient exchange between the soil and the tree's root system.

The fungus acts as an ectomycorrhizal partner. It colonizes the outer layers of the root tips, forming a mantle that protects the roots and increases the absorption area for water and essential minerals, which is vital for the growth of Alnus species in wetland habitats.

Signs of its presence include the emergence of small, brown to ochre-colored fruiting bodies near the base of alder trees. These mushrooms feature the characteristic cobweb-like veil typical of the Cortinarius genus, which is most visible in young specimens before the cap expands.

Developmental conditions are strictly linked to the ecological niche of the host tree. The fungus thrives in moist, humus-rich soils where humidity levels remain high. It prefers temperate climates and is typically observed during late summer and autumn seasons when moisture is abundant.

No protective measures are required as this species does not cause crop damage or plant disease. Instead, it is a marker of a healthy forest ecosystem. Management practices should focus on maintaining natural soil moisture and avoiding soil compaction to preserve the integrity of the mycorrhizal network.