Geopyxis

Geopyxis is a genus of fungi belonging to the Pyronemataceae family. While many species are known as saprotrophs living on decaying organic matter, some species like Geopyxis carbonaria are pyrophilous fungi. In forestry, they are sometimes documented as agents affecting the health of coniferous seedlings planted in nurseries established on former forest fire sites.

The causal agent is an ascomycete that thrives in soil containing charcoal and ash. Its biological cycle is closely tied to burnt substrates, which provide specific chemical conditions necessary for the development of the fungal mycelium and the subsequent formation of fruit bodies.

The primary hosts affected by this fungus include various coniferous species such as pines and spruces. The fungus targets the root system and the root collar area of the seedlings, often causing physiological stress by disrupting the uptake of water and nutrients from the soil, leading to stunted growth.

Symptoms of the infection involve the yellowing and wilting of the needles, which eventually results in the desiccation of the plant. A diagnostic feature during the active growth phase is the emergence of small, yellow-to-brown, cup-shaped apothecia on the soil surface surrounding the base of the young plants.

The development and spread of the fungus are facilitated by high soil moisture, cool weather, and the accumulation of burnt woody debris. Spores are easily disseminated by wind, allowing the fungus to colonize adjacent areas within a short period, particularly if the environmental conditions are favorable.

• Removal of charcoal and burnt organic residues from the site before planting.
• Regular inspection of seedling root systems in forest nurseries.
• Implementation of crop rotation to avoid pathogen accumulation.
• Use of soil fungicides in nurseries with documented occurrences.
• Ensuring optimal drainage to prevent excessive moisture retention.