Greenhouse xylaria

Greenhouse xylaria (latin: Xylaria vaporaria) is a significant pathogenic fungus that poses a major threat to mushroom cultivation, particularly affecting the common button mushroom (Agaricus bisporus). As an ascomycete fungus, it colonizes the growing medium, outcompeting the commercial mycelium and rendering the substrate unproductive.

This pathogen primarily targets mushroom farms where the environmental conditions of the casing layer are not strictly monitored. Once established, the fungus rapidly colonizes the compost, effectively suffocating the beneficial mycelium and consuming the nutrients intended for the mushroom harvest.

The visible symptoms of infection include the appearance of a gray-white, web-like mycelium mat on the surface of the casing soil. As the infection matures, it develops distinctive black, branched stromata that resemble small antlers or clubs. When these structures appear, the commercial production of mushrooms in the affected beds typically ceases immediately.

Favorable conditions for the development of this pathogen include high humidity, stagnant air, and poorly composted or inadequately pasteurized substrate. It is often introduced into growing rooms through contaminated casing materials, unsterilized tools, or through the movement of air carrying spores from infected areas outside the facility.

Protection and preventive strategies focus on maintaining a high level of hygiene within the facility. Growers must ensure that substrate pasteurization processes are strictly followed to eliminate initial contaminants. Regular sanitation, using recommended disinfectants for the tools and room structures, along with the isolation of any identified outbreak sites, remains the primary approach to managing the spread of the fungus.