Key Technical Points for Mimicking Wild, Pollution-Free Cultivation of Maitake (Grifola frondosa)

Crop straw and forestry by-products accumulate in enormous annual quantities, providing abundant raw materials for the production of edible fungi. How to produce pollution-free, safe, high-quality, pollution-free edible fungus products is an important issue facing the edible fungus industry. The following introduces pollution-free cultivation techniques for mimicking wild maitake (Grifola frondosa), based on the national pollution-free edible fungus production technical standards.

Optimal selection of cultivation sites and raw materials: edible fungi have a strong ability to accumulate harmful heavy metals, so cultivation sites and raw materials for maitake must be carefully selected to minimize the accumulation of harmful substances brought about by the cultivation site and raw materials. ① Optimal selection of cultivation site. The cultivation site should be chosen in a place with good air circulation and open surroundings, far from major traffic roads, industrial and mining enterprises, poultry and livestock farms, hospitals, and other pollution sources; the air quality should meet the national ambient air quality standards, and the water source should be clean and unpolluted. ② Optimal selection of cultivation raw materials. Choose fresh, mold-free, pest-free cottonseed hulls, sawdust, corn cobs, rice straw, spent mushroom substrate, etc., rich in cellulose and hemicellulose, as the main materials, and use wheat bran, cornmeal, humus soil, etc., as auxiliary materials. The main and auxiliary raw materials must not have been treated with highly residual pesticides within 1 month before harvest, and their heavy metal content must not exceed standards; aged materials should be sun-dried for 2-3 days before use to kill molds and insect eggs and reduce the base number of contaminating microorganisms and pests.

Standardize the operation of the cultivation process. ① Cultivation period. The arrangement of the cultivation season is closely related to the yield and quality of maitake, and when cultivating, the timing of spawn production and substrate bag preparation should be arranged according to local climatic conditions. Maitake is a mesophilic fungus and is mostly cultivated in spring and autumn. In northern regions, spring cultivation generally produces mushrooms from April to June, and autumn cultivation from November to December. In southern regions, spring cultivation generally produces mushrooms from March to April, and autumn cultivation from November to December. From inoculation to fruiting generally takes about 55 days, so the timing of making the spawn bags should be about 2 months earlier than the optimal fruiting time. ② Culture medium formula. Maitake is suitable for cultivation with a variety of raw materials, but broadleaf tree sawdust and cottonseed hulls as the main materials give the best results; adding an appropriate amount of mountain soil containing humus to the culture medium is more suitable for the growth of maitake and can increase the formation rate of maitake fruiting bodies. Four formulas are provided here. First, mixed hardwood sawdust 77%, wheat bran 10%, cornmeal 10%, sucrose 1%, gypsum powder 1%, calcium carbonate 1%. Second, mixed hardwood sawdust 44%, cottonseed hulls 44%, wheat bran 10%, sucrose 1%, gypsum powder 1%. Third, mixed hardwood sawdust 40%, cottonseed hulls 30%, wheat bran 10%, cornmeal 8%, hillside soil 10%, sucrose 1%, gypsum powder 1%. Fourth, cottonseed hulls 60%, wheat bran 20%, soybean cake powder 8%, vegetable garden soil 10%, sucrose 1%, gypsum powder 1%. The moisture content should be controlled at 60%-65%, and the pH value at 5.5-6.5. ③ Bagging and sterilization. Cultivation bags mostly use 16 cm x 30 cm x 0.03 cm polypropylene plastic bags. Mix the raw materials according to the formula proportions, add water and adjust the moisture content, stir evenly, and then fill into plastic bags. When filling the bags, attention must be paid not to crush or puncture the bags; after compressing the medium and smoothing the surface, make a hole in the material (to facilitate air permeability), put on a plastic collar, and then plug with a cotton plug. After bagging is completed, it should be sterilized in a pot promptly; high-pressure sterilization needs to be maintained for 10 hours. ④ Inoculation and mycelial growth. Select high-yield, high-quality spawn and inoculate under aseptic operation. After inoculation, place in a spawn-running room, keep warm at 25-28°C, indoor relative humidity 60%-70%, culture in the dark, and ventilate 1-2 times daily. After 15 days, add scattered light, strengthen ventilation, and keep the temperature at 22-25°C. After 30 days, the mycelium will have grown to the bottom of the bag and formed a mycelial skin on the surface, and it can then enter fruiting management.

Mimicking wild fruiting. ① Time for arranging the spawn sticks. After the mycelium has fully colonized the bags, remove the plastic bags and arrange the spawn sticks neatly in previously dug beds. This soil-covered cultivation form can achieve a biological efficiency of 100%-120%, far superior to bag-style fruiting. The best time for arranging maitake spawn sticks into the ground is from November to the end of April of the following year. ② Method for arranging the spawn sticks. In the optimally selected cultivation woodland, dig pits 45-55 cm wide, 2.5-3 cm long, and 25 cm deep, with a distance of 60-80 cm between pits, and build drainage ditches in between. After the trenches are dug, irrigate once with a large amount of water; after the water seeps away, spread a layer of lime powder on the bottom and sides of the trench to increase calcium and disinfect. Peel off the plastic bags from the fully colonized spawn bags, and place the spawn sticks in the trench in rows horizontally and vertically; adjacent spawn sticks should be placed tightly together, with a gap between every 4 spawn sticks. In the trench, 4-5 rows of spawn sticks can be arranged. Then spread a layer of fresh plant ash on the surface of the bed, the purpose being to increase fertilizer and inhibit the growth of contaminating microorganisms, which can increase yield by more than 10%.

Scientific management of fruiting. ① Water. When the natural temperature reaches above 15°C, irrigate once in the bed, with the water amount preferably submerging the bed surface by 2 cm; afterward, spray water once each in the morning, noon, and evening every day, and spray into the air as much as possible. If the weather is relatively dry, water once every 5-7 days. When spraying water in low-temperature seasons, it is best to use warm water warmed in sunlight to help maintain temperature. ② Temperature. The suitable temperature for the growth of maitake fruiting bodies is 16-20°C. When the temperature is relatively low, extend the time of direct sunlight on the bed surface during the day, and cover the straw curtains tightly at night. When the temperature is relatively high, cover with straw curtains during the day when the temperature is high, and uncover the straw curtains at night to grow in the open air. ③ Ventilation. During the growth period of maitake fruiting bodies, attention should be paid to ventilation in the shed. When the weather is relatively warm, uncover the straw curtains for ventilation for 2-3 hours every day. Note that ventilation should be reduced in low-temperature and windy weather, and ventilation should be appropriately increased before and after spraying water in the morning and evening. During the primordium differentiation stage, ventilate less and maintain moisture more; during the primordium growth stage, ventilate more to promote evaporation. ④ Light. It is necessary to maintain stable scattered light for the growth of maitake, with a suitable light intensity of 200-500 lux. Air and sun-dry for 1-2 hours every morning and evening to increase weak direct light; avoid strong direct light during the fruiting period, and do not remove the straw curtains for convenience of operation. The four major factors of light, temperature, water, and air must be coordinated. An uncoordinated environment easily causes deformed mushrooms.

Prevention and control of pests and diseases. ① Prevention and control of pests and diseases. Maitake has a relatively long fruiting period and is prone to pests and diseases, so the principle of "prevention first, comprehensive control" must be adhered to. Create the best growth environment conditions suitable for maitake growth to ensure robust growth of maitake. Biological control is advocated: in the preparation of the culture medium, plant antibacterial agents and botanical pesticides may be used, such as botanical pesticide insecticides and acaricides made from the Chinese medicinal herb perilla, the composite plant pyrethrum, and the woody oil plant rapeseed, etc. Parasitic nematodes are used to control fleas, gall midges, and sciarid flies, etc. Implement physical control: use 30-watt ultraviolet irradiation or ozone sterilizers for disinfection and sterilization in the cultivation site. Always maintain environmental hygiene and spread lime powder for disinfection. Strictly and scientifically use pesticides: when chemical pesticides must indeed be used, choose pesticides already registered for use on edible fungi, such as kemeling and meideke. Pesticides should be applied before fruiting or after each flush of mushrooms is harvested. ② Emergency prevention and control measures. For pests and diseases occurring during the maitake cultivation process, emergency prevention and control measures should sometimes be taken: green mold is the most likely to occur and the most harmful contaminating microorganism; once it occurs, it causes a large yield reduction in mild cases and total loss in severe cases. When local infection is found, the infected part is usually dug out, a small amount of limewater is sprinkled, and moist new soil is added. When there are many infected parts, 5% plant ash water can be used to irrigate the bed surface once. When insect pests such as mushroom flies are found, spread plant ash onto the bed surface and use low-toxicity, high-efficiency pesticides to kill the insects, and there must be no residual toxicity hazard. In high-temperature seasons, when mucus-like spawn sticks appear on the bed surface, spray the bed surface with 1% bleaching powder solution to inhibit bacteria. ③ Strengthen product quality testing. Fresh mushrooms after harvest should have substrate roots and impurities removed, and be inspected according to the pollution-free edible fungus product quality inspection rules; after passing inspection, they should be packaged according to pollution-free packaging requirements, and the pollution-free mark should be affixed.