Brown plaster mold

The causative agent of this disease is the microscopic fungus Papulaspora byssina, which belongs to the imperfect fungi. In the mushroom industry, this disease is commonly known as "brown plaster mold." While it is not a direct parasite of the mushroom fruit bodies, it acts as a severe competitor in the compost, hindering the normal growth and colonization of the mushroom mycelium.

The primary crop affected by this pathogen is the button mushroom (Agaricus bisporus) during artificial cultivation in indoor facilities. The fungus thrives within the substrate and on the surface of the casing soil, depriving the mushroom mycelium of essential nutrients and space, which inevitably leads to a significant reduction in overall yield.

Symptoms of the infection appear as specific white, which later turn into golden-brown, fluffy patches on the surface of the casing soil. Unlike the healthy mushroom mycelium, the colonies of Papulaspora byssina have a denser structure and a distinct color caused by the mass formation of bulbils — specialized cells that allow the fungus to survive under adverse environmental conditions.

The development of the disease is triggered by failures in maintaining proper temperature and humidity levels within the growing rooms. The fungus spreads rapidly in high-humidity environments and thrives when compost pasteurization is incomplete. Major infection vectors include contaminated casing materials, poorly prepared substrates, or poor sanitary practices by personnel during the cultivation process.

The economic impact of this disease lies in its ability to completely block the growth of the mushroom mycelium, leading to heavy losses or total crop failure in affected trays. Effective management requires strict sanitation, thorough disinfection of premises, rigorous compost pasteurization, and the prompt removal of infected areas, as chemical control measures are often ineffective against established outbreaks of this mold.

• Excessive air humidity.
• Inadequate substrate pasteurization.
• Spore spread via equipment.
• Insufficient facility disinfection.
• Contaminated casing soil.