I. Pathogens and Conditions
Bacterial brown spot disease in edible fungi is primarily caused by *Pseudomonas aeruginosa*, a bacterium commonly found in natural environments. This pathogen thrives in high-temperature and high-humidity conditions, especially in poorly ventilated growing areas. When the temperature exceeds 18°C or the relative humidity goes beyond 85%, bacterial multiplication accelerates. During the fruiting stage, water contaminated with the bacteria can be sprayed onto the mushroom caps and the growing medium. Poor ventilation, excessive moisture, and long-term accumulation of moisture on the cap surface and culture medium increase the risk of infection. Repeated planting of the same species in greenhouses over multiple years, along with condensation from plastic films, can also lead to bacterial growth and disease outbreaks. Additionally, the bacteria can become airborne and spread through mushrooms, nematodes, and human activities.
II. Main Symptoms
1. Contamination of the Culture Medium: Infected agar media develop visible colonies that appear as raised, irregular patches on the surface. These eventually rot and mold. In bag cultures, contamination leads to increased moisture, a sour smell, and later, decayed materials with a strong acidic odor.
2. Mushroom Body Infection: The infected mushroom caps show irregular brown spots, often round or diamond-shaped, with neat edges and slightly sunken centers. A thin layer of bacterial film or pus may cover the lesions, which can be scraped off with a fingernail, revealing white flesh underneath. In severe cases, dozens to hundreds of lesions may appear on a single cap, causing the mushroom to wrinkle, stop growing, and eventually rot when excess moisture is present.
III. Comprehensive Prevention Measures
1. Maintain a Healthy Growing Environment: Cultivation areas should be located away from poultry houses to avoid contamination. Avoid spreading manure or contaminated sticks around the area. Regular sterilization of the mushroom house is essential. Bed frames and support structures should be cleaned and bleached. Disinfect the room using a 150 mg/L bleach solution. Before placing the mushroom bags in the shed, fumigate the space with 10–15 g/m³ of sulfur for 2–3 days. Keep the relative humidity below 85% and ensure good ventilation during the growing phase. Use drip-proof plastic films to reduce condensation.
2. Select High-Quality Cultures: Use non-contaminated, fungus-free, and mildew-free substrates. During hot seasons, keep bran content below 10%, avoid adding corn flour, and add an appropriate amount of lime. Ensure the moisture content of the substrate does not exceed 65%. Maintain air humidity below 70% during strain cultivation. Disinfect soil-covered materials with formaldehyde.
3. Choose Resistant Strains: Opt for varieties with strong resistance to contamination. Plan the planting season carefully, ensuring timely inoculation. Avoid planting too early in autumn or too late in spring.
4. Manage Water During Fruiting: Keep the growing area dry and improve ventilation to maintain proper humidity. Avoid spraying water directly on mushroom buds during the budding stage. If watering is necessary, use disinfected water (150 mg/L bleach) that has been left to sit for one day. Prevent water from coming into contact with the medium or fruiting bodies.
5. Remove Infected Mushrooms: As soon as any mushroom in the shed shows signs of infection, it must be removed immediately, including young, infected buds. When removing the mushrooms, take out the entire root and clean the surface of the culture medium to prevent further nutrient consumption by the pathogen.
6. Chemical Control: 1. For mild infections, spray the affected areas with 2000 times diluted agricultural streptomycin. 2. Apply 150 mg/kg chlorine to the mushrooms to reduce disease incidence. 3. Spray the surface of the medium or the fruiting body with 3000 times diluted "Mushroom Guard" liquid, applying it every 7–10 days. Mix with 3000 times diluted "Mushroom Guard" to prevent infection throughout the growth cycle. 4. Use 2000 times diluted "Mushroom Disease Nemesis" to spray the mushrooms.
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