Detailed Guide to Identifying and Controlling Common Mushroom Diseases

I. Fungal Diseases

1. Brown rot. Also known as white rot and blister disease. The pathogen spores are brought into the mushroom house through casing soil and spread by air and insect pests. When the air in the mushroom house is not circulating and high temperature and high humidity occur, the disease is severe. A large amount of white mycelium forms on the mushroom bed. After infection, the stipe of the fruiting body swells into a blister-like shape, and in severe cases deformed mushrooms form, turning brown, or white flocculent spherical masses form in which the cap and stipe are indistinguishable. Control method: mainly disinfect the casing soil. Place the casing soil in an empty room and fumigate at a ratio of 5 ml of formaldehyde plus 3 g of potassium permanganate per sq m for 24 hours before use. If diseased mushrooms are found on the mushroom bed, watering should be stopped immediately, ventilation should be increased and the temperature lowered to below 15°C, with humidity not exceeding 85%, and 1%-2% formaldehyde solution should be sprayed in the affected area. For severely affected mushroom beds, the casing soil should be replaced, the diseased mushrooms burned, and the tools used disinfected with 4% formaldehyde solution.

2. Soft rot. Caused by infection with Mycogone perniciosa. Most pathogen spores are spread by airflow and splashing water droplets, and this disease is prone to occur when the casing soil is too wet and conditions are low temperature and high humidity. When the disease occurs, if it is not treated promptly, the pathogen spreads rapidly and turns water-red. After the fruiting body is infected, it gradually turns brown until it rots. Control method: reduce watering on the bed surface, strengthen ventilation of the mushroom house, lower the humidity of the soil surface and air, sprinkle lime or spray 4% formaldehyde solution on the affected parts; carbendazim or thiophanate or 500-fold kuiyangling solution may also be sprayed.

3. Brown spot. Also called dry blister disease and Verticillium disease, caused by Verticillium fungi. The pathogen spores often stick together in clumps and are mainly spread by splashing water droplets and mushroom flies, mites, hands, tools, and so on. This disease mostly occurs in the later stage of cultivation. After onset, many irregular needle-like brown spots first appear on the cap, and afterward the spots gradually expand and become sunken, with the sunken parts appearing grayish-white. Diseased mushrooms often dry and crack, the cap becomes skewed and deformed, and peeling occurs on the stipe. However, the mushroom body does not rot and has no special odor. Control method: strictly prevent mushroom flies from entering the mushroom house; disinfect all tools with 4% formaldehyde solution; spray 500-fold carbendazim solution, etc., on affected areas.

II. Bacterial Diseases

1. Spot disease. Caused by Pseudomonas tolaasii. This pathogen is widely distributed in nature and is spread by insect pests and workers. It is prone to occur under high temperature and high humidity, and occurs more severely in summer and autumn. In the early stage of the disease, yellow-brown discolored areas appear in one or two places on the cap, and then quickly become dark brown sunken spots. The key to controlling this disease is to properly control the relative humidity of the air. Especially in the later stage of mushroom growth, the humidity in the mushroom house should not exceed 85%, and water accumulation on the cap surface and excessively wet soil surface should be avoided. Reduce temperature fluctuations, preferably below 17°C. After onset, spray 600-fold bleaching powder solution.

2. Dry rot. Also called dry stiff disease, it is also caused by a Pseudomonas bacterium. Mushrooms in the affected area are deformed, pale brown, with skewed caps and swollen bases of the stipes, and gradually shrink and dry up, losing edible value. Control method: mainly isolation, preventing mycelial connection between diseased and disease-free areas. In box cultivation, if the mycelia between mushroom boxes do not connect, dry rot will not spread; on mushroom beds, separating sections with plastic film can also block its spread.

III. Physiological Diseases

1. Hard opening. The phenomenon in which mushrooms encounter abnormal climate and young fruiting bodies open their caps early is called hard opening. It generally occurs below 18°C, with a temperature difference of about 10°C, or under sudden temperature drops. Control method: do a good job of heat preservation before sudden temperature changes and increase the relative air humidity in the mushroom house.

2. Deformed mushrooms. The causes are uneven thickness of the casing soil and low fruiting position; carbon dioxide content in the mushroom house exceeding 0.3%, as well as phytotoxicity and diseases and insect pests. Control method: pay attention to the quality of the casing soil and ventilation, prevent harmful gases from entering the mushroom house, and pay attention to the control of diseases and insect pests.

3. Thin-skinned mushrooms. They can occur throughout the entire fruiting stage. They are mainly caused by excessively high or low temperature in the mushroom house, or excessive ventilation on the bed surface. Control method: strengthen ventilation during high temperatures, and keep the mushroom house warm and humid during low temperatures or strong winds.

IV. Viral Diseases

Viral diseases are spread through diseased spores and mycelia. After mycelia are infected with the virus, they cannot form fruiting bodies; after mushroom primordia are infected with the virus, the fruiting bodies develop deformities, or the stipes become unusually long and the caps open extremely early, or the stipes bend and the caps are especially small, or the lower part of the stipe is sharply tapered, or the middle of the stipe swells into a barrel shape or jar shape, ultimately causing the mushroom body to wither and shrivel into a sponge-like state. On mushroom beds severely infected with the virus, large blocks without mushrooms often appear. Control method: after viral disease is found, mushrooms must be completely harvested before the caps open to prevent spores released by diseased mushrooms from spreading; fumigate all cultivation bed racks with low-dose methyl bromide; boil and disinfect all utensils. If the disease occurs and spreads severely, according to the highly specific nature of viral parasitic infection, changing the cultivated species can eliminate this disease.