Symptom Identification and Key Control Points of Mushroom Wet Bubble Disease

Mushroom wet bubble disease is also known as wet rot, blister disease, white mold disease, and so on. It is a disease that occurs commonly worldwide. The pathogen is Mycogone perniciosa, also called Mycogone perniciosa (causing cap wart mold), belonging to the class Hyphomycetes, order Moniliales, family Moniliaceae, genus Mycogone. When mushroom mycelium begins to twist and form small mushroom primordia, it is most susceptible to infection; upon infection, the small mushroom primordia become tumor-like masses formed by the interwoven growth of mushroom mycelium and pathogen mycelium, resembling a puffball in appearance, commonly called "mushroom blister" by mushroom growers, and generally fruiting 3—4 days earlier than normal mushrooms. The symptoms and key control points of mushroom wet bubble disease are as follows:

I. Symptoms of Mushroom Wet Bubble Disease

Long-term research has found that this pathogen only infects the fruiting bodies and does not attack the mycelium. From initial infection of the mushroom to the first appearance of symptoms requires a minimum of about 11 days. Growing mycelium can accelerate and stimulate the germination of Mycogone spores. When the first flush of mushrooms becomes diseased, the source of infection is usually the casing soil and old mushroom shelves; when later flushes become diseased, it is caused by re-transmission through water, tools, and human operations.

If infected during the primordium formation stage, the manifestation is: before normal primordia appear, diseased mushrooms grow in large numbers, forming an abnormal puffball-like tissue mass; diseased mushrooms generally fruit 3-4 days earlier than normal mushrooms. If infected by the pathogen during the young primordium growth stage, although the diseased mushrooms can continue to grow, the caps develop abnormally or stop developing, the stipes swell and become distorted and deformed, and in the later stage the interior becomes hollow; at the junction of the cap and stipe and at the base of the stipe, white cottony mycelium grows out, which then turns dark brown, with brown droplets exuding from the surface, causing rot and giving off a foul odor.

II. Key Control Points of Mushroom Wet Bubble Disease

1. Casing soil is the main transmission medium of Mycogone, so disinfecting the casing soil is the key to controlling the occurrence of wet bubble disease. Casing soil material should preferably be soil taken from below 15 cm beneath the surface, so as to avoid bringing pests and diseases from the surface layer into the mushroom house. In areas where wet bubble disease occurs severely, river mud, pond mud, and similar materials containing large amounts of Mycogone spores should not be used. After the casing soil material is brought back, expose it to the sun until dry; when using it, evenly mix it with a 1/1000 formaldehyde aqueous solution, using about 2 kg of industrial formaldehyde per cubic meter of casing soil, until the soil particles are moist, then cover tightly with plastic film for one day, then spread it out to air for one day to let the formaldehyde evaporate before use. If steam is used to disinfect the casing soil, it can be kept at 65 degrees C for 1 hour.

2. Mushroom house treatment. The mushroom house should be located far from garbage dumps, pig and cattle sheds, and other places with abundant pests and diseases. If the compost is subjected to a second fermentation inside the mushroom house, steam disinfection can be carried out in combination with pasteurization. If the second fermentation is not carried out inside the mushroom house, formaldehyde can be used for disinfection, fumigating 12 hours at 10 ml formaldehyde and 2 g potassium permanganate per cubic meter. Or use an aerosol disinfection box at 2-4 grams per cubic meter and fumigate for more than 2 hours.

3. After casing the mushroom beds and before fruiting, evenly spray benzimidazole pesticides in the mushroom house and surrounding environment, which can effectively prevent the occurrence of wet bubble disease. Commonly used pesticides include carbendazim, thiophanate-methyl, thiabendazole, prochloraz, and wet bubble net, etc., at a dilution of 500-1000 times. In recent years, the "high-efficiency fungicide" developed by the Fujian Province Mushroom Spawn Research and Extension Station has been widely adopted across the province, with good results.

4. Treatment of diseased mushroom beds. If wet bubble disease occurs over a large area, stop watering immediately and dig out the diseased mushrooms and Mycogone mycelium masses on the mushroom bed. Fumigate the mushroom house with formaldehyde or an aerosol disinfection box for 1 hour, using the same amounts as above; note that fumigation must not last too long. Immediately after fumigation, ventilate for 2-3 days; wait until the surface of the mushroom bed is dry, then evenly spray the above-mentioned benzimidazole pesticides at the same dilution as above. Be sure to spray the surface casing soil thoroughly and evenly, and also spray the surrounding environment evenly; after adjusting the water again, normal fruiting can still occur. If wet bubble disease occurs only to a small extent, promptly remove the diseased mushrooms and Mycogone mycelium masses, and evenly spray benzimidazole pesticides on the affected areas.

5. Strengthen mushroom house management; during periods of high temperature and high humidity, pay attention to ventilation and air exchange, and promptly dispose of the removed diseased mushrooms.