Penicillium, commonly known as green mold, is a genus of fungi that includes several species frequently encountered in the production of edible mushrooms. Among them, *Penicillium frequentans*, *P. lilacinum*, *P. viridicatum*, and *P. chrysogenum* are particularly common. These molds can cause serious damage to oyster mushrooms, button mushrooms, and other edible fungi during both seed production and cultivation stages.
**1. Symptoms of Damage**
In the early stages of infection, the mycelium of Penicillium closely resembles that of the edible mushroom, making it difficult to distinguish between the two. However, once conidia (spores) begin to form, Penicillium becomes more recognizable due to its pale blue or green powdery appearance. Once the mold contaminates the substrate, it suppresses the growth of the edible mushroom's mycelium, preventing fruiting body formation. Even if fruiting bodies do develop, they often become discolored, brown, and eventually rot.
**2. Morphological Features**
The mycelium of Penicillium is usually colorless or light in color and grows in separated strands. The conidiophores are erect, resembling bristles, with symmetrical branches that may be bifurcated or multi-branched. At the tip of these structures, conidiospores are formed. These spores are typically spherical or oval, single-celled, and may have smooth or rough surfaces. Their color varies from colorless to green or even other hues. The colonies generally appear green, yellow-green, or blue, and new white growth rings are often seen on the outer edges of the colony.
**3. Occurrence Patterns**
Penicillium is highly adaptable and widely distributed. It produces a large number of spores that spread through air, soil, fertilizers, and plant debris. This fungus not only affects edible mushrooms but also acts as a major pathogen in agricultural products, causing issues like mold during storage, fruit rot, and deterioration of flower bulbs. Penicillium thrives in temperatures between 20–30°C, with relative humidity above 90%, and prefers acidic environments.
**4. Prevention and Control Measures**
Maintaining good hygiene in the growing area is crucial. Regular cleaning and disinfection of the inoculation room and mushroom houses should be carried out. Operators must ensure thorough sterilization during the seed production process, and care should be taken when handling bagged cultures to avoid rupturing the plastic bags. Routine inspections should be performed, and any contaminated strains should be removed immediately to prevent further spread.
If Penicillium appears on the mushroom bed, increasing ventilation and reducing humidity by keeping the temperature around 20–22°C can help control the infection. Once the mold is suppressed, normal management can resume. Adjusting the pH of the medium by adding 1–3% quicklime or spraying 2% lime water during preparation can also inhibit microbial growth.
Chemical treatments such as 0.1% thiophanate-methyl-based dry materials are effective for control. Good ventilation in the mushroom house and farm is essential to avoid high humidity and temperature conditions that favor Penicillium growth. In localized cases, applying a 5–10% lime water solution or lime powder to the affected areas can help reduce contamination. Another method involves removing the infected part first and then spraying a 3–5% copper sulfate solution to kill the mold.
Bioantibody Biotechnology Co., Ltd. , https://www.bioantibodymedical.com