Control Methods for Competitive Contaminant Fungi in Edible Mushrooms

Edible mushroom pests and diseases refer to the microorganisms and insect pests that compete with edible mushrooms for nutrients and space, harm their growth and development, and cause declines in the yield and quality of edible mushrooms.

Competitive contaminant fungi and their control:

(1) Contaminants during the spawn-making period are a series of competitive fungi that compete for the nutrients in the substrate, and some also produce toxins that affect mycelial growth. Common ones include Aspergillus, Penicillium, Trichoderma, Rhizopus, and bacteria.

1. Common contaminant fungi

(1) Neurospora: also called Neurospora sitophila, with orange-red or pink spores, hence also known as red Neurospora. It is a moderately high-temperature aerobic fungus. Under suitable conditions it grows extremely fast and spreads rapidly, and it often occurs in mushrooms cultivated on media such as sawdust and cottonseed hulls. Its main harm is competing with edible mushrooms for nutrients and space. It often grows on the cotton plugs at the bag mouth and on the surface of the bags. The mycelium can develop in depth, and after the mycelium fills the bag it naturally disappears, with little effect on fruiting; however, if it cross-infects with Trichoderma, the harm is extremely great.

(2) Aspergillus: there are mainly three kinds, Aspergillus flavus, Aspergillus niger, and Aspergillus glaucus. The colony shape is yellow-green in the middle with a ring of white around it. It is a moderately high-temperature type at 25-30°C, prefers high humidity and a slightly acidic environment. When the mycelium grows well it can be covered over, with little effect on fruiting. Its main harm is competing with edible mushrooms for nutrients and space.

(3) Penicillium and Paecilomyces: the colony color is more blue-green, with white around it. They compete with edible mushrooms for nutrients and space, and are more harmful than Aspergillus.

(4) Mucor and Rhizopus: the mycelium looks like rotten cotton wadding, and Rhizopus produces rhizoids. They are a sign that the moisture content of the substrate is on the high side. Their main harm is competing with edible mushrooms for nutrients and space.

(5) Trichoderma: produces green spores, and the colony appears green, hence also called green Trichoderma. It can secrete enzymes that have a destructive effect and produces exotoxins, often causing log rot, and the harm is extremely great.

(6) Bacteria: the substrate has a fishy, foul odor from rotting organic matter, mostly bacterial contamination.

2. Causes of contaminant fungi

The main causes of contaminant fungi are: the bag mouth is not tied tightly, sterilization is not thorough, the substrate is not fresh or the humidity is on the high side, aseptic technique is not strictly followed during inoculation, bags are loosened or punctured during handling, the culture environment is not thoroughly disinfected, the concentration of contaminant fungal spores in the environment is high, the primary infection sources are abundant, too much water is sprayed during management, air humidity is high, the environment is poorly ventilated, and the temperature is on the high side. All of these are the main causes of contaminant fungi. The main cause of bacteria is incomplete sterilization.

3. Main control methods for contaminant fungal contamination

Prevention and control of edible mushroom pests and diseases. Edible mushrooms are a health food. Because their production cycle is short, and many edible mushrooms are not removed from the bag during cultivation, they are neither suitable for applying medication nor for general pesticides, and the effects are also not great. Therefore, the prevention and control of edible mushroom pests and diseases must adhere to the policy of "prevention first, integrated control," with the main emphasis on prevention. The control mainly includes the following aspects: First, a site with fresh air, a clean location, good ventilation, cool and dry conditions, a clean water source, and far from warehouses and livestock and poultry sheds with no pollution sources should be chosen as the cultivation site; second, do a good job of environmental sanitation. To prevent contaminant fungi, operators must strictly observe aseptic operating procedures, do a good job of environmental sanitation and disinfection in the inoculation room and culture room, and disinfect the site in advance strictly with agents such as formaldehyde, rotating the agents regularly; third, strictly require aseptic technique and ensure the aseptic step is well controlled; fourth, for bags contaminated with miscellaneous fungi, use centralized treatment such as deep burial, composting, or burning.