What are the control methods for Penicillium in edible fungi?

Penicillium, also known as green mold, common species in edible fungus production include Penicillium frequentans, P. lilacinum, P. viridicatum, P. chrysogenum, and P. verruculosum. Penicillium can infect and harm various edible fungi such as oyster mushrooms, button mushrooms, and shiitake mushrooms during both spawn production and cultivation.

(1) Damage symptoms In the early stage of infection, the pathogen mycelium is extremely similar to the edible fungus mycelium, making it very difficult to distinguish the two. However, after conidia form, Penicillium appears as a light blue or green powdery layer. After Penicillium infects the mushroom bed and contaminates the substrate, it inhibits the growth of edible fungus mycelium, preventing fruiting body formation, and even if fruiting bodies form, it causes them to turn brown and rot.

(2) Morphological characteristics The mycelium is colorless or light-colored, with septa. The erect conidiophores are symmetrically dichotomously branched or multi-branched in a broom-like shape, with phialides produced at the tips, bearing conidia in chains. The conidia are spherical or oval, single-celled, with smooth or rough surfaces, colorless, green, or with other mixed colors. Colony colors include green, yellow-green, blue, etc., and a white new growth zone is commonly seen at the outer edge of the colony.

(3) Occurrence patterns Penicillium has strong adaptability and wide distribution, produces large quantities of conidia, and the spores spread through air, soil, fertilizer, plant residues, etc. Penicillium is not only an important contaminant fungus of edible fungi but also a major pathogen of agricultural products, often causing mold in stored grain, fruit rot, and quality deterioration of flower bulbs. The suitable growth conditions for Penicillium are a temperature of 20-30°C, relative air humidity above 90%, and it prefers to grow in acidic environments.

(4) Control methods Pay attention to environmental sanitation, keep the surroundings of the culture room and the cultivation site clean, and dispose of waste materials promptly. The inoculation room and mushroom house should be cleaned and disinfected according to regulations; during spawn production, operators must ensure thorough sterilization, and bagged spawn should be handled gently during transport to strictly prevent plastic bags from breaking; conduct frequent inspections and promptly remove contaminated spawn, and never sow diseased spawn. If Penicillium occurs on the mushroom bed substrate, ventilate and dry promptly, control the room temperature at 20-22°C, and resume routine management after the contaminant fungus is suppressed. Adjust pH by appropriately raising it; adding 1%-3% quicklime during substrate mixing or spraying 2% lime water can inhibit contaminant fungus growth. For chemical mixing into the substrate, using 0.1% of the dry material weight of thiophanate-methyl provides better control results. Also pay attention to ventilation and air exchange in the mushroom house and mushroom yard to avoid high temperature and high humidity; when the disease occurs locally, wipe with 5%-10% lime water or sprinkle lime powder on the affected area, or first dig it out and then spray 3%-5% copper sulfate solution to kill the pathogen.