Simplicillium lamellicola

Simplicillium lamellicola is a pathogenic fungus that causes significant damage in commercial mushroom cultivation. Historically classified within the Verticillium genus, this organism acts as a specific parasite of fungal fruiting bodies. It is widely recognized by mycologists and agronomists as a primary cause of severe crop losses in Agaricus bisporus farms.

The disease primarily impacts the common button mushroom. The fungus infects the mushroom at various developmental stages, hindering growth and altering the morphology of the host. Because it is highly contagious within the closed environment of a growing house, even a small initial infestation can rapidly evolve into an epidemic if not contained.

Symptoms of the infection are characterized by severe deformity of the mushrooms, including thick, stunted stems and misshapen caps. An infected mushroom typically develops a white, velvety coating of mycelium and spores on its surface. As the infection progresses, the tissues become necrotic, often turning light brown or tan in color, which eventually renders the crop commercially unsalable.

The development of the fungus is strictly dependent on environmental conditions. It thrives in high-humidity environments (above 85% RH) and temperatures ranging from 18°C to 24°C. The pathogen is disseminated through airborne spores, contaminated casing soil, or by mechanical transmission via tools and workers. In some cases, sciarid flies and phorid flies act as biological vectors for the disease.

Effective management and prevention strategies rely on a comprehensive sanitation program:

• Ensuring thorough pasteurization of the casing soil and compost substrate to eliminate dormant spores.
• Strict access control to growing rooms to prevent cross-contamination.
• Immediate removal and disposal of infected mushrooms to prevent further sporulation.
• Rigorous disinfection of harvesting tools, carts, and footwear between rows and different growing chambers.