Common abnormal phenomena and handling measures in oyster mushroom cultivation in late spring and early summer

Late spring and early summer is a good season for cultivating oyster mushrooms. However, due to improper operations, some mushroom growers experience abnormal phenomena such as yellowing and necrosis of mushroom logs after fruiting, souring and stinking of the substrate, and delayed fruiting after the mycelium has fully colonized the bags, which reduces the success rate, yield, and quality and directly affects economic returns. Based on many years of production practice and the experience of growers, the author summarizes the causes of these abnormal phenomena and the handling measures as follows.

1. Mass death of young mushrooms after fruiting from the mushroom bags

In late spring and early summer, sometimes after the mushroom logs fruit, young mushrooms turn yellow and soft in large numbers, their bases thicken, and then they wither and rot into dead mushrooms. Causes: First, after the mulberry-shaped primordia form, the air temperature remains high and exceeds 30°C, causing the caps to gradually wither and resulting in mass death of young mushrooms; second, the substrate is too dry and the relative air humidity is too low. If, after the young buds form, the relative air humidity in the fruiting room or shed is below 80%, the young mushrooms shrink and die because the mushroom tissue loses water rapidly through evaporation in large amounts; third, poor ventilation and a rapid increase in carbon dioxide concentration in the fruiting room (shed). When it exceeds 0.5%, large-foot mushrooms with caps as large as a fist or thick stalks and small caps will form. When the carbon dioxide concentration is even higher, the young mushrooms will be suffocated to death; fourth, excessive watering makes the young mushroom bodies prone to waterlogging, after which they turn yellow and rot, causing infection by pathogens and death from disease.

Handling measures

First, during the fruiting period, when the air temperature is too high, cooling measures should be taken. Well water can be sprayed on the floor and surroundings of the fruiting room or shed to lower the temperature below 30°C. Outdoor mushroom sheds should be shaded with thicker straw curtains or rice straw, and ventilation and air exchange management should be strengthened; second, after the mushroom bags form buds, the relative air humidity in the fruiting room or shed should be raised to about 90%, and water should be sprayed 4 to 5 times per day. Each spraying should be done sparingly, finely, frequently, and evenly. When the buds are young, never spray water directly on the mushroom bodies; third, as the fruiting bodies grow, ventilation and air exchange should be strengthened. Especially during high-temperature periods, even more attention should be paid to ventilation to ensure fresh air in the fruiting room or shed; fourth, the amount of water sprayed must be properly controlled. Water should neither be withheld nor sprayed excessively. Increasing air humidity is mainly done by frequently sprinkling water on the floor and walls, and direct spraying on young fruiting bodies should be avoided as much as possible.

2. Only one end of some substrate bags grows mycelium

When the same spawn is inoculated into both ends of a substrate bag, often only one end grows mycelium well, while the mycelium at the other end shrinks and dies. Causes: First, the sterilization stove is built unreasonably, so condensed water cannot flow back into the pot along the stove wall, but instead flows irregularly into some bag mouths, causing the substrate at that end to absorb too much water and inhibiting mycelial growth; second, the substrate bags are placed too close to the stove wall, and the pot is filled with too much water, leaving too little space between them, which obstructs steam circulation. Condensed water flows from the stove wall into the bag mouth at one end, making the substrate at that end too wet and hindering mycelial growth.

Handling measures

First, the top of the stove should be built into a round arch so that condensed water flows back into the pot along the stove wall; second, there should be a certain distance between the arranged substrate bags and the stove wall to prevent water from entering; third, the substrate bags should not be arranged too densely, so as to speed up steam circulation and improve sterilization effectiveness; fourth, for substrate bags sealed only with rubber bands or string, after the mycelium is established, the tied mouth should be loosened somewhat to increase aeration. Plastic neck rings with paper covers are best for sealing the mouth, avoiding mycelial death caused by oxygen deficiency. Fifth, a hole should be made in the middle of the substrate bag, and spawn (especially wheat grain spawn) should be inoculated directly into the hole, avoiding direct contact between the spawn and the plastic bag and preventing the spawn from being soaked to death by condensed water on the bag wall.

3. Delayed fruiting after the mycelium has fully colonized the bags

In some mushroom bags, the mycelium grows very vigorously, but after the mycelium has fully colonized the bags, fruiting is delayed. Some still do not form buds after 2 to 3 months. Causes: First, improper selection of spawn. Medium- and low-temperature-type varieties were cultivated in late spring and early summer; second, the carbon-to-nitrogen ratio of the substrate is unsuitable; third, when subculturing the mother culture, too much aerial mycelium was picked, causing the stock culture and cultivation spawn to clump, which seriously affects fruiting body formation; fourth, after the mycelium has fully colonized, under conditions of relatively high temperature and relatively low air humidity, the bag mouth was opened too early, causing a thick dry mycelial membrane to form on the surface, so that mushroom buds could not differentiate.

Handling measures

First, high-temperature-type oyster mushroom varieties should be cultivated in late spring and early summer. If medium- and low-temperature-type oyster mushroom varieties have been cultivated, the two ends of the substrate bags should be tied tightly, and the bag mouths should be opened to fruit only after the temperature drops in autumn, which can reduce losses. Alternatively, the plastic bags can be removed, and the mushroom logs can be arranged closely horizontally in a moist, cool place, covered with a layer of broken soil about 2 cm thick, and covered with straw curtains, which can also produce mushrooms in large quantities; second, rationally formulate the carbon-to-nitrogen ratio in the substrate. During the mycelial stage of oyster mushrooms, the more suitable carbon-to-nitrogen ratio in the substrate is 20:1. During the fruiting body stage, the required carbon-to-nitrogen ratio is preferably 30 to 40:1. If the carbon-to-nitrogen ratio in the substrate is imbalanced, with too much nitrogen and insufficient carbon, vegetative growth will be excessive, causing rapid mycelial growth. In severe cases, it may even become dense and clumped, forming a mycelial skin, inhibiting reproductive growth, delaying fruiting, and affecting yield. Wheat bran, rice bran, tubers, soybean cake, corn, and the like contain relatively abundant nitrogen, and the amount added should be controlled appropriately. If the carbon-to-nitrogen ratio of the substrate becomes imbalanced, the dense mycelial clumps on the surface should be scratched off, and carbon-containing substances such as 0.5% glucose or (0.5 to 1) x 10-6 triacontanol should be sprayed to adjust the carbon-to-nitrogen ratio. At the same time, strengthen ventilation, light, and greater temperature difference stimulation, which can promote budding and fruiting as soon as possible; third, the number of subcultures of the mother culture should not be too many; fourth, if a thick mycelial membrane forms on the surface of the mushroom log and affects fruiting, holes can be punched in both ends of the mushroom bag with iron wire, then the dry mycelial membrane on the surface can be scratched off with a small rake, and the mushroom bag soaked in water below 25°C for 8 to 12 hours. After it has absorbed enough water, it should be rearranged on the shelves, given ventilation, light, and temperature difference stimulation, and air humidity should be increased, and it will also fruit quickly.

4. A large number of mushroom buds appear in the middle of some substrate bags. Causes:

First, the substrate is not packed tightly, and there are gaps between the substrate and the bag; second, during sterilization, the pressure is too high, bursting the substrate bag or causing it to bulge; third, the substrate bag is punctured during filling or transport; fourth, during the mycelial growth stage, unsuitable culture conditions, such as too great a temperature difference, relatively strong light, or relatively high air humidity, can all promote the formation of fruiting body primordia in the middle of the substrate bag.

Handling measures

First, when filling the substrate, compact it while filling, tight outside and loose inside, so that the substrate is in close contact with the bag wall with no gaps left; second, handle filling and transport carefully to avoid damaging the substrate bags, and release gas slowly after steaming the substrate; third, create suitable environmental conditions for mycelial development. The culture room should be shaded, maintain a constant temperature, and keep relative humidity at about 70%. The spawn culture room and the fruiting site should be separated.

5. Occurrence of mushroom burning. Causes:

Mushroom burning occurs when the temperature in the mycelial growth environment is too high. For example, when the culture room temperature reaches above 30°C, it exceeds the range of mycelial viability. When the room temperature reaches 40°C, mushroom burning will occur in the mushroom logs, causing mycelial death.

Handling measures

The culture room should maintain constant-temperature mycelial incubation, and the temperature must not exceed 30°C. When the temperature in the culture room exceeds 30°C, the stacks should be turned promptly and ventilation used to lower the temperature. To avoid mushroom burning, summer cultivation is best carried out in a cool indoor place, and mushroom bags are best arranged in a single layer. Insert a thermometer into the bag to observe changes in substrate temperature. If the temperature is relatively high, sprinkle some cold water on the floor promptly, open doors and windows for ventilation, and take cooling measures. It should be pointed out that the temperature inside the substrate is generally 3 to 5°C higher than room temperature, which should be noted.

6. Fruiting before the mycelium has fully colonized the bags. Causes:

First, unsuitable environmental conditions during the mycelial culture stage, such as substrate that is too dry or too wet; packing too tightly during filling; poor nutrient content in the medium; too strong light; too great a temperature difference; unsuitable pH; or spawn that is too old, all of which reduce mycelial viability.

Handling measures

Create the best conditions suitable for mycelial growth and development, including formulation, water content, pH, temperature, light, and so on, all of which must suit the needs of vegetative growth; second, select high-quality, pure white, thick, and vigorous spawn.

7. The substrate turns sour and stinks

After the substrate is bagged, sterilized, and inoculated with spawn, a sour, stinking odor is emitted from the substrate, affecting mycelial growth. Causes: First, the substrate is not fresh and clean enough and carries a large amount of contaminating microorganisms, especially when old substrate is used. When disinfection and sterilization are not thorough, various molds in the substrate multiply and breed in large numbers, causing the substrate to sour and spoil and producing an unpleasant sour, stinking odor; second, too much water is used when mixing the substrate, and oxygen supply within the substrate is insufficient, allowing anaerobic bacteria and yeasts to multiply, causing the substrate to rot and deteriorate; during the mycelial culture stage, because the substrate bags are stacked, the substrate temperature rises, accelerating the growth rate of contaminating microorganisms; third, wheat grain spawn is in close contact with the substrate bag, and condensed water on the bag wall soaks the wheat grains, causing the spawn to rot; fourth, the nitrogen nutrition in the substrate is too high and reacts chemically with the added lime, producing an ammonia odor.

Handling measures

First, before cultivation, select good raw materials and use fresh, clean substrate with no mold or clumping. Before mixing, expose it to sunlight for 2 to 3 days; second, control moisture when mixing the substrate. Do not make it too dry or too wet. The ratio of cottonseed hulls to water is preferably 1:1.3 to 1.4, and the amount of water added to other crop straw is preferably 1:1.4 to 1.5. Add 0.1% to 0.2% fungicides such as carbendazim or thiophanate-methyl to the water; third, for substrate with too strong a sour, stinking odor, pour it out of the bags early, add 2% lime water to adjust it to a pH of about 7.5 and a water content of about 60%, and re-inoculate and cultivate it; fourth, if the ammonia gas is too strong, add 2% alum water and mix well to remove the odor. A 10% formalin compound solution may also be sprayed to remove the odor; fifth, if the substrate has already rotted and turned black, it can only be used as high-quality fertilizer in fields and cannot be used for cultivation. Odors dispersed around the cultivation site can be removed by spraying a deodorizer. The deodorizer formula is: 5 parts ferrous sulfate, 95 parts sodium bisulfate, ground into powder and fully stirred at room temperature.