Black spot is a bacterial disease caused by Pseudomonas. After the onset of disease, the mushroom mushroom caps appear oval brown or dark brown spots, the initial needle-like, enlarged diameter of 2 to 4 mm, neat edges, and sometimes cracked cap. Control methods: control the temperature and humidity. When watering the mushroom house, do not sprinkle water directly on the fruit body of the mushroom and do not spray it with cold water. The humidity in the mushroom house should not exceed 90% for a long time. It depends on weather changes. The sunny days should be light, hard and fine, and the rainy days should be less or not. Each time after watering should be enhanced ventilation, and then cover the film. The indoor temperature during the mushrooming period should be adjusted to about 17°C. Mushrooms should be removed in time after onset and sprayed with 100 to 200 international units of streptomycin for agriculture or 600 times for bleaching powder for prevention and treatment.