Myceliophthora thermophila

Myceliophthora thermophila is a thermophilic fungus recognized as a destructive pathogen in the commercial cultivation of Agaricus bisporus (button mushrooms). It is colloquially known as the agent responsible for "white plaster mold," a condition that severely compromises mushroom productivity.

The fungus acts as a competitor to the mushroom mycelium within the compost and casing layer. By colonizing the substrate, it depletes available nutrients and secretes inhibitory substances, effectively suffocating the healthy mushroom spawn and preventing the development of fruit bodies.

Symptoms typically manifest as dense, white or yellowish mycelial patches appearing on the surface of the casing soil. As the infection progresses, these areas become crusty and dry, mimicking the appearance of dry gypsum or plaster. The presence of the pathogen is often accompanied by a distinct, musty odor that signals an imbalance in the substrate microflora.

The development of Myceliophthora thermophila is highly favored by elevated temperatures, particularly in the range of 35°C to 45°C. These conditions often occur if the composting process is faulty or if ventilation is inadequate. The fungal spores are highly resilient, allowing the pathogen to persist in cultivation facilities and spread rapidly via contaminated tools, clothes, or airflow.

Management and prevention focus primarily on strict adherence to composting pasteurization protocols. Essential steps include:

• Ensuring thorough heat treatment of all mushroom substrate.
• Maintaining high standards of farm hygiene to prevent cross-contamination.
• Utilizing clean, disinfected casing material.
• Monitoring temperature gradients closely during the spawn-run phase.