The Harm and Control Methods of Common Contaminant Fungi in Edible Mushroom Cultivation

I. Neurospora. Also known as Monilia. Its asexual stage belongs to the order Moniliales, family Sphaeriaceae; its sexual stage is an ascomycete. The species harmful to mushrooms are Neurospora crassa and Neurospora sitophila. The hyphae are white, loose, branched and septate. The conidiophores branch in a dichotomous manner. The conidia are produced in chains, spherical to oval, orange-red or pink. The perithecia are clustered or scattered, nearly spherical or oval. The asci are cylindrical, each containing 8 ascospores. Neurospora is widely distributed and can be spread through air, soil, decaying plants, grains, and so on. It occurs severely when the substrate is too wet and the cotton plug becomes damp. It can contaminate the stock cultures, mother cultures, and cultivation cultures of all mushrooms, as well as the logs for shiitake, wood ear, and silver ear. On contaminated cultures and substrate, grayish-white slender hyphae first appear, growing rapidly; after a few days, orange-red powdery spore masses form on the outside of the bottles or bags, clearly rising above the surface of the substrate. This often causes entire batches of cultures to be discarded. Control methods: maintain good sanitation, sterilize the substrate thoroughly, avoid dampening the cotton plug, and do not damage the bags during handling. Strictly follow aseptic procedures, and avoid high temperature and high humidity in the culture room. Inspect regularly; when spore masses are found, first cover them with wet paper, then carry them out and burn them.

II. Trichoderma. Also known as green mold. Order Moniliales, family Moniliaceae. The species harmful to mushrooms are Trichoderma viride and Trichoderma koningii. The hyphae are colorless and septate. The conidiophores arise from side branches of the hyphae, erect, septate; the small branches are often opposite, and the terminal phialides are flask-shaped, bearing conidial heads. The conidia are spherical or oval, pale green. The harm Trichoderma does to mushrooms includes: contaminating the substrate and competing with the mushrooms for nutrients; secreting toxins that poison the mushroom hyphae; and entwining or severing the mushroom hyphae. It is widely distributed and is a worldwide harmful fungus. Its harmful period is long, and the mushrooms are attacked throughout their growth process. The degree of harm is great, and it can cause a complete loss of an entire batch of mushrooms. Trichoderma is found in decaying wood, plant residues, organic fertilizers, air, and soil. Conditions with excessive carbohydrates in the substrate, acidity, and high temperature and high humidity favor its occurrence. Residual stumps left after harvesting mushrooms are also easily infected. Control methods: keep the culture room at low temperature, low carbon dioxide, and well ventilated. Choose Trichoderma-resistant varieties. Do not let the air humidity in the mushroom house exceed 90%. After harvesting, promptly remove debris and root stumps. At the early stage of infection, spray 0.1% carbendazim solution or 800-fold benomyl solution. Mixing 0.1% carbendazim or thiophanate-methyl into the substrate can prevent its occurrence.

III. Penicillium. It also belongs to the order Moniliales, family Moniliaceae. The species harmful to mushrooms are Penicillium citrinum, Penicillium chrysogenum, and others. The hyphae are colorless or colored, with cross septa. The conidiophores are septate, bearing brush-like branches, with phialides at the tips; the phialides produce conidia in chains, and the conidia are spherical or oval, pale green. Penicillium can grow on many organic materials. Its conidia are mainly spread by air and can occur year-round, especially severely in summer. On contaminated substrate, it forms circular colonies, dark green to blue-green, downy, and spreading relatively slowly. When colonies are dense, they join into patches. Old colonies often interweave to form a membranous substance, blocking air from the substrate surface and secreting toxins that have a lethal effect on the hyphae. It can also induce mushroom diseases. Control methods: see the control of Neurospora and Trichoderma.

IV. Aspergillus. It also belongs to the order Moniliales, family Moniliaceae. The species harmful to mushrooms are Aspergillus niger, Aspergillus flavus, Aspergillus glaucus, and others. The hyphae are colorless and septate. The conidiophores are non-septate and unbranched, with the tip swelling into a spherical or oval shape, densely bearing phialides in a radial arrangement; the conidia are produced in chains on these, spherical or oval, black (Aspergillus niger), yellow-green (Aspergillus flavus), or pale green (Aspergillus glaucus). Aspergillus is distributed in soil, air, and various organic materials. It readily occurs under high temperature, high humidity, poor ventilation, and when there are excessive carbohydrates in the substrate. On contaminated substrate, white fuzzy hyphae first appear, quickly turning into a colored powdery mold layer. It not only competes with the mushrooms for nutrients and water but also secretes toxins, seriously affecting mushroom yield and quality. Control methods: the same as the control of Neurospora and Trichoderma.