Symptoms and Control Methods of Oyster Mushroom Brown Blotch Disease
Mushroom brown blotch disease is also known as dry blister disease, Verticillium mold, and so on. In some areas the disease occurs rather severely, and yields suffer great losses.
Damage symptoms: when mushroom buds are affected, their growth and development are poor, so that the stipes and buds cannot form and become shriveled white small mushroom masses. When fruiting bodies are affected, many pinhead-sized brown spots appear on the caps, and later the spots enlarge and become sunken, grayish-white in the center; when moist, white moldy growth, namely conidiophores and conidia, forms on the lesions. When the stipe is affected, the stipe base becomes thicker and brown, the outer tissue peels and splits, and after growing up the stipe base becomes crooked and deformed.
Pathogen: this disease is caused by infection by Verticillium fungicola, a fungus of the subdivision Deuteromycotina. The mycelium is grayish-white; conidiophores grow out from the mycelium, and conidia are borne at the tips of the sterigmata, oval or elliptical in shape.
Occurrence pattern: the pathogen mainly enters the mushroom house through soil, such as casing soil, and can also be brought into the mushroom house by mushroom flies, mites, tools and manual operations. After the disease occurs, conidia are produced and spread by watering, airflow and insects. High temperature and high humidity favor the disease; with much watering, poor ventilation and high humidity in the casing layer before pinning, the disease generally occurs.
Control techniques
1. Agricultural control
(1) For disinfection of the compost, use secondary fermentation, which both favors the growth of mushroom mycelium and inhibits the growth of Verticillium mold.
(2) For disinfection of the casing soil, high-humidity treatment can be used, treating at 60°C for 1 hour.
(3) Take measures to prevent insects from entering, and prevent mushroom flies and mites from entering the mushroom house.
(4) Control temperature and humidity. While maintaining the normal temperature of the mushroom house, open the windows for ventilation and air exchange to reduce humidity. Pay attention to the casing layer; humidity should not be too high. After watering, ventilate promptly to reduce humidity.
(5) Remove diseased mushrooms promptly. When diseased mushrooms are found, immediately dig out the diseased mushrooms together with the mycelium and the compost to a depth of 10 cm, carry them out of the mushroom house or field and burn them, fill the diseased holes level with sterile soil, and at the same time disinfect all tools with 4% formaldehyde to prevent the spread of the fungus.
2. Chemical control
(1) Spraying liquid medicine. Before the mushrooms grow out, spray the casing soil and bed surface with 600 times dilution of 50% benomyl wettable powder. In the early stage of the disease, spray 500 times dilution of 50% carbendazim wettable powder, or 600 times dilution of 20% thiophanate-methyl wettable powder, or 600 times dilution of 60% Fangmeibao wettable powder.
(2) Replace diseased soil and apply chemical control. For severe cases, the diseased soil can all be dug off, replaced with disease-free new soil and re-cased, and measures taken to reduce the temperature and humidity in the bed. If necessary, remove all mushrooms, bury or burn the diseased mushrooms deeply, let the mushroom bed soil dry for several days, then spray the bed surface with 2% formalin, and after the formalin volatilizes, water again. Note: disinfect all tools with 4% formalin (formaldehyde) solution; spraying formalin easily causes phytotoxicity, so be especially careful: first, the concentration should not be high; second, do not sow immediately (generally after an interval of 14 days); the soil should be turned and ventilated to let the chemical volatilize, preventing phytotoxicity.