False truffle

Diehliomyces microsporus is a detrimental fungal pathogen widely known as the "False truffle" disease. It specifically targets Agaricus bisporus, the common button mushroom, posing a severe threat to commercial mushroom farms and indoor production systems worldwide.

The causative agent belongs to the Ascomycota group. It acts as a parasite that consumes the nutrient-rich substrate intended for the mushroom mycelium. Once the pathogen establishes itself in the compost, it rapidly outcompetes the healthy mycelium, leading to a complete halt in mushroom fruit body development.

The visual symptoms typically appear as white, dense mycelial mats that eventually thicken into lumpy, yellowish or tan structures. These structures are the fruiting bodies of the fungus, which bear a superficial resemblance to truffles, hence the common name. Infected compost often produces a distinct, stale odor and fails to produce any commercial mushrooms.

The development of this disease is highly dependent on environmental conditions, specifically high moisture levels and temperatures ranging from 20 to 25 degrees Celsius within the compost. The spores of the fungus are exceptionally resilient and can persist in cracks, equipment, and even on the clothing of workers, making containment a significant challenge.

Effective prevention and control start with rigid hygiene protocols. It is essential to ensure that the composting process reaches appropriate temperatures during pasteurization to eliminate all pathogenic spores. If an outbreak occurs, the affected beds must be immediately quarantined. Once the production cycle is finished, thorough steaming of the entire room is necessary to eradicate any remaining traces of the fungus before the next crop is planted.