Causes and Control Methods of Penicillium Mold in Edible Mushrooms

In nature, Penicillium spores are everywhere, and in our edible mushroom production, every production step can potentially become infected with Penicillium. Today let's take a look at what the causes and control methods of Penicillium mold in edible mushrooms are.

I. Causes of Penicillium mold in edible mushrooms

The Penicillium commonly seen in edible mushroom production mainly refers collectively to Penicillium citrinum, Penicillium funiculosum, Penicillium chrysogenum, Penicillium cyclopium, Penicillium pallidum, Penicillium digitatum, and Penicillium italicum, and can also be understood as a collective term for a class of fungi in the genus Penicillium. During the mycelial growth stage, most conventionally cultivated edible mushrooms are easily infected by Penicillium; only when the fruiting bodies suffer serious disease and their resistance declines will it show up on the fruiting bodies of the edible mushrooms.

The mycelium is colorless or pale, with septa. The upright conidiophores are symmetrically dichotomously or multiply branched in a broom-like shape, producing sterigmata at the tips, which give rise in chains to conidia. The conidia are spherical or oval, single-celled, with smooth or rough surfaces, colorless, green, or tinged with other miscellaneous colors. The color of the colonies is green, yellow-green, blue, and so on, and a white new growth band is commonly seen on the outer ring of the colony.

The Penicillium species harmful to edible mushrooms all belong to the Deuteromycete Penicillium fungi. When the pathogen grows in large numbers, the colonies appear blue-green.

The pathogen is widely distributed, mostly saprophytic or weakly parasitic, existing on many kinds of organic matter, producing large numbers of conidia, and mainly entering the culture substrate through airflow to cause primary infection. Contaminated raw and auxiliary materials are also an important source of primary infection in raw-material cultivation. The conidia produced after infection cause secondary infection by means of airflow, insects, artificial watering, and management operations. High temperatures favor the disease, which occurs most easily at 28°C-30°C; the conidia can germinate in 1-2 days to form white mycelium and rapidly produce conidia. Most Penicillium species prefer an acidic environment, and the disease is more likely to occur when the culture substrate and casing soil are acidic. Weak growth of edible mushrooms favors the disease; wherever young mushrooms grow thin and weak or mushroom stubs remain on the bed and are not removed in time, the pathogen is more likely to infect.

II. What are the control methods for Penicillium mold in edible mushrooms?

1. Carefully carry out disinfection and sterilization of the inoculation room, culture room, and production site, keep the environment clean and sanitary, strengthen ventilation and air exchange, and prevent the spread of the disease.

2. Adjust the culture substrate to an appropriate pH. For cultivating button mushrooms, oyster mushrooms, and shiitake mushrooms, the culture substrate can be adjusted to slightly alkaline with 1%-2% limewater. After harvesting mushrooms, spray limewater to stimulate the growth of edible mushroom mycelium and inhibit the occurrence of Penicillium.

3. During spawn production, operators must ensure thorough sterilization, and bagged spawn must be handled gently during transport and other processes to strictly prevent the plastic bags from breaking.

4. For localized disease in mushroom bags, a 15% formaldehyde solution can be injected; when Penicillium occurs on log sections, they can be washed with limewater; for disease on the mushroom bed, a 1% procymidone (Kemeiling), 0.5% Duofengnong, 0.1% Shibaogong, and 0.1% iprodione (Puhaiyin) solution can be sprayed for control.