Papulaspora stoveri

Papulaspora stoveri is a recognized fungal pathogen that primarily affects the commercial production of mushrooms, specifically Agaricus bisporus. It is classified as a competitive mold that colonizes the substrate and casing layer, causing significant economic losses in mushroom farms by inhibiting the growth of the desirable fungal mycelium.

The host range is largely concentrated on cultivated mushrooms within controlled environmental facilities. The pathogen competes for space and nutrients, effectively reducing the yield potential of the crop. Because it is highly opportunistic, it can quickly colonize compost that has been insufficiently pasteurized or has lost its selective properties.

Symptomatology involves the appearance of white, fluffy mycelial patches that eventually turn into brown, granular structures known as bulbils. These structures are the hallmark of Papulaspora stoveri and are easily distinguishable from the healthy white, rhizomorphic or cottony mycelium of the cultivated mushroom. These patches can rapidly spread across the surface of the casing soil.

Environmental conditions conducive to disease development include high humidity, stagnant air, and improper temperature regulation within the cropping rooms. The pathogen thrives in environments where organic debris remains on the floor or where the casing material has high moisture content without proper ventilation, allowing the spores and bulbils to germinate and expand rapidly.

Control and prevention are primarily based on rigorous hygiene and strict adherence to technical protocols:

• Ensuring thorough pasteurization of the casing layer and substrate.
• Implementing strict sanitation programs for all tools and surfaces.
• Optimizing climate control, particularly moisture management and air circulation to prevent stagnant spots.
• Prompt isolation and sanitation of contaminated areas to limit the spread of the pathogen's propagules.