Mushroom Topdressing Methods and Key Points of Pest and Disease Control

(1) Cultivate and select high-quality spawn. High-quality spawn: First, the strain must be good, possessing the characteristics of high yield, high quality, and strong stress resistance (including resistance to pests and diseases); second, the purity must be high, with no pest or disease infection. The most fundamental thing is still to cultivate new varieties and new strains with strong disease and pest resistance; third, the spawn age must be appropriate. Aged spawn not only has poor vitality but also has a higher probability of contamination. When selecting spawn, if the latter two points are neglected, this is often one of the main causes of severe pest and disease infection during the spawn-making or mycelium-running period. For example, the mycelium of straw mushroom (Volvariella volvacea) is slender and not dense, grows quickly, but is prone to aging and autolysis. If the mycelium in the bottle shrinks, or partial mycelium shows signs of autolysis, or the spawn age exceeds 30 days, it is aged spawn. After sowing aged spawn, not only does the mycelium recover slowly, grow poorly, and yield low, but it is also susceptible to pest and disease infection. Therefore, the spawn age should preferably be around 20 days. The suitable spawn age for shiitake (Lentinula edodes) spawn is best used as soon as the mycelium fully covers the bottle, usually at 45-50 days. With this kind of spawn, after inoculation the mycelium germinates quickly, has strong vitality, and the contamination rate is low.

(2) Adjust to a suitable pH. Regarding pH requirements, edible mushrooms mostly prefer a slightly acidic or neutral environment, except straw mushroom which prefers alkaline conditions. However, most pathogenic bacteria prefer a neutral or slightly alkaline environment. Therefore, when making spawn, an appropriate amount of superphosphate can be added to make the culture medium slightly more acidic, which can both inhibit the occurrence of pathogens and supply a certain amount of phosphorus for the edible mushrooms. If some pathogens that prefer alkaline conditions, such as white plaster mold and brown plaster mold, are found on the mushroom bed, superphosphate can be directly sprinkled on the affected material surface.

After sowing straw mushroom, the culture material tends to change from alkaline to acidic. Based on the characteristic that straw mushroom prefers an alkaline environment, in combination with watering and after each flush of mushrooms is harvested, lime water at pH 9 can be sprayed to meet the pH requirements for straw mushroom growth, while also inhibiting the occurrence of Coprinus species that compete with straw mushroom for nutrients and moisture. This is because Coprinus species prefer an acidic environment and grow poorly in a neutral or slightly alkaline environment. For some mushrooms that can also grow well in a neutral or slightly alkaline environment, such as button mushroom (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus), the raw materials used in cultivation (rice straw, cottonseed hulls, etc.) can be mixed with 1%-2% lime water, and after harvesting mushrooms, lime water (supernatant) can also be sprayed.

(3) Strengthen cultivation management to improve the disease and pest resistance of edible mushrooms. The management during the mycelium-running period should aim to both promote the growth of edible mushroom mycelium and inhibit the occurrence of pathogens. The main measures taken are:

① Properly lower the temperature during cultivation. Most pathogens prefer high temperatures, while edible mushrooms, except straw mushroom, require lower temperatures. Therefore, after inoculation, the cultivation temperature should be controlled below 25°C. Properly lowering the temperature during cultivation, although the mycelium grows more slowly, makes it thick and strong, while pathogens are significantly reduced.

② Lower humidity during cultivation. Edible mushrooms also require relatively low air relative humidity during the mycelium growth stage. Therefore, during the mycelium-running period, the air relative humidity should be maintained at around 60%, which can effectively inhibit the occurrence of pathogens.

③ Turn and inspect the bags in a timely manner. Seven days after inoculation, turn and inspect the bags once. For those found to be infected by pathogens, bags with mild infection can be injected at the affected area with 75% alcohol or a 1:3 formaldehyde solution; for those with severe infection, use a bag slightly larger than the original spawn bag to cover them, tie tightly, and re-sterilize and re-inoculate. Never remove the contaminated logs from their bags, sun-dry them, and reuse them, which would let pathogen spores fly everywhere and cause severe repeated infection.

During the fruiting period management, attention should be paid to scientific water use, as unclean water is a medium that can spread pathogens. Therefore, for water management in the mushroom house, first, the water used must be clean; when this cannot be guaranteed, a 150 mg/L bleaching powder solution can be sprayed. Second, watering should combine promotion and control, spraying more when needed and less when needed. After casing soil, lightly spray and spray frequently in the early stage, and only spray heavily for fruiting water when mushrooms are about to appear. During the fruiting period, spray more when there are many mushrooms and less when there are few.

After watering the mushroom bed, ventilation should be carried out in combination. Most pathogens prefer high temperature and high humidity. Once disease appears on the mushroom bed, watering should be stopped and ventilation increased.

In addition, the suitable ecological conditions of the mushroom house, such as light, temperature, water, and air, should be well regulated so that the edible mushroom mycelium grows vigorously, enhancing vitality and improving stress resistance, so that with vigorous growth it can inhibit the occurrence and spread of pathogens.