Control Methods for Diehliomyces microsporus in Edible Fungi

Diehliomyces microsporus, also known as calf brain disease or false truffle, mainly damages mushrooms.

(1) Damage symptoms Mostly occur on the casing surface and in the casing layer before and after casing. First, short and dense white hyphae appear, then ascomata resembling walnut meat form one by one. The ascomata grow in clusters on the casing surface and in the compost layer, competing with mushrooms for nutrients and hindering the formation of mushroom fruiting bodies. When the ascomata mature, the asci rupture and release large numbers of ascospores. When this fungus occurs in mushroom spawn bottles, the bottles give off a bleaching powder smell.

(2) Morphological characteristics The hyphae are white, thick, septate and branched. The ascomata are composed of hyphae, dense, with veins and gaps, shaped like walnut meat or calf brain, with irregular wrinkles on the surface. They are initially milky white small round dots, gradually becoming irregular masses, and dark red when mature. Asci are borne inside the ascomata; the asci are oval to spherical, irregularly arranged, and contain 8 ascospores each. The ascospores are colorless and nearly spherical.

(3) Occurrence pattern It mainly exists in soil and enters the mushroom bed via the site, compost, casing soil or spawn. The suitable temperature for hyphal growth is 26-30°C, the suitable temperature for ascospore germination is 24-27°C, and the suitable pH is 4.5-7.5. High temperature and high humidity favor the occurrence of this fungus. The ascospores are resistant to high temperature, and the high temperature of after-fermentation has no killing effect on the spores. If the mushroom house temperature is kept below 18°C, this disease can be avoided.

(4) Control methods Strictly inspect the spawn to avoid spawn carrying the fungus; the first fermentation must be carried out on a concrete floor to avoid contamination by the pathogen; pay attention to ventilation and air exchange in the mushroom house. After the disease occurs in the mushroom bed, stop spraying water on the bed surface, and after the casing soil dries slightly, dig out the ascomata, lower the room temperature to below 16°C, and then follow routine management; mushrooms can still be produced normally.