Detailed Explanation of the Key Technical Points for Black Fungus (Wood Ear Mushroom) Cultivation and Management
Log Cultivation
1. Tree selection: Many tree species are suitable for the growth and development of black fungus. However, one should adapt to local conditions and choose tree species that are abundant in local resources and easy for fungus to grow on. Except for tree species containing pine resin, essential oils, alcohols, ethers, and economic forest trees, all other tree species can be used for cultivating wood ear fungus. Currently, commonly used tree species include cork oak, sawtooth oak, Mongolian oak, warty birch, Castanopsis carlesii, Chinese wingnut, sweetgum, elm, black locust, willow, Catalpa, plane tree, and Chinese pistache. However, cork oak and sawtooth oak are the best.
2. Tree felling: The historical custom is to fell trees during the "entering the nines" period (the coldest days of winter). Generally speaking, felling can be done from when the leaves turn yellow and wither until before new leaves sprout, because this period is precisely the tree's "dormancy" period. During this time, the nutrients in the trunk are in a state of accumulation and non-flow, with less water and the most abundant and concentrated nutrients. This is called felling "sap-collected trees." At the same time, trees felled during this period have bark and xylem tightly bound together, so the bark is not easily detached after felling, which benefits the growth and development of black fungus.
As for the age of trees to be felled: those growing on sunny slopes should be 7-8 years old, and those growing on shady slopes or in poorer soil should be 8-10 years old. The best trunk diameter is around 10 cm, and the length is 1 m. One rack holds 50 logs.
For the felling method, the stump should be left low, 10-15 cm above the ground; the axe should cut from both sides of the trunk, leaving the stump in a "crow-beak" shape. This benefits the regeneration of old stumps, as it will neither accumulate water and rot the sprouts nor cause multiple sprouts to compete and affect stump regeneration. When felling, it is advocated to cut with a pulling stroke rather than a sweeping stroke, which both helps protect young trees and benefits soil and water conservation.
3. Branch removal: After the tree is felled, do not remove branches immediately. Keeping the branches and leaves can accelerate the evaporation of water from the tree, promote rapid drying of the trunk, and cause its cell tissues to die, while also helping nutrients in the treetop concentrate into the trunk. Wait ten days to half a month before removing branches. When removing, use a sharp axe to shave flat from bottom to top against the trunk, cutting into "copper coin scars" or "ox eye scars." Do not cut too deep and damage the bark layer. The scars after cutting should preferably be coated with limewater to prevent invasion of foreign fungi and water accumulation, and also to facilitate stacking and arrangement.
4. Log cutting: In order to facilitate stacking, arranging, racking, management, and harvesting of the fungus logs, and also to allow the logs to absorb moisture from the ground when laid down, overly long trunks should be cut into short logs 3 chi long. When cutting, use a hand saw or chainsaw to cut them into even ends, and coat with limewater to prevent fungal infection.
5. Rack drying: Rack drying means stacking the cut wooden logs in a place with high, dry terrain that is well-ventilated and sunny, into a "well"-shaped or "fish-back"-shaped pile about 1 m high, letting them quickly lose water and die. During rack drying, turn them inside and out, top and bottom, about once every 10 days to promote even drying of the fungus logs. The rack drying time should be flexibly controlled according to tree species, log thickness, and climatic conditions. Generally, rack drying for 1 month to 1.5 months, until the logs have lost 30-40% of their moisture compared to before rack drying, is sufficient for inoculation.
6. Fungus yard selection: The place where fungus racks are arranged is called the fungus yard. The quality of the fungus yard environment directly affects the growth and development of black fungus and its final yield. Generally speaking, it is best to choose a wind-sheltered mountain hollow facing south with its back to the north. This place has long daily sunlight hours and small day-night temperature differences; morning and evening often have cloud and mist cover, high humidity, and air circulation, making it most suitable for the growth and development of black fungus. When selecting the site, it should also be close to a water source to facilitate artificial watering. The slope should preferably be 15-30 degrees. Absolutely avoid choosing places with rocky surfaces, chalk soil, or iron-alumina soil. After the site is selected, it should first be cleared: thin out overly dense trees in the area, cut away shrubs, thorny vines, and easily rotting weeds, leaving only a small number of tall broadleaf trees with small crowns or sparse branches and leaves to provide appropriate shade for the fungus racks in summer. Before planting, apply insecticide to the ground and disinfect once with bleaching powder and quicklime; in winter, it is best to burn the site with firewood and grass. Do not remove the sheep's beard grass, turf, moss, etc. growing on the site, in order to prevent soil erosion and maintain the moisture of the fungus yard.
7. Inoculation: Inoculation means planting artificially cultured mycelium spawn onto the rack-dried fungus logs, so that it develops and colonizes within the logs and grows fruiting bodies. This is the most critical step in artificial cultivation of black fungus and is a major technical innovation in production, with quick results and high yield. When inoculating, first disinfect the fungus yard and fungus logs (using disinfectants or fire will do; disinfect tools with alcohol or boiling water; workers can wash with soapy water). Choose a shaded place to proceed; do not let direct sunlight hit the spawn, and absolutely do not do it on rainy days. The inoculation time is generally from February to early May, and in autumn it can be done between White Dew and Cold Dew. When inoculating, choose different tools according to different spawn types, such as branch spawn or triangular wood spawn; use a cutting axe to cut notches, insert sawdust together with branch or triangular wood into the notches, and tap gently with the back of the axe, with the principle of not falling out; for sawdust spawn or granular spawn, use a 10 mm electric drill, hole puncher, or hollow punch to make holes, insert the spawn into the holes, cover with bark, and tap gently tight. For inoculation density, generally row spacing is 2 cun, plant spacing is 2.5-3 cun, arranged in a "pin" shape or staggered into a plum-blossom shape. The density at both ends of the log should be greater, so that mycelium can quickly occupy the territory and avoid invasion by foreign fungi. The depth of inoculation should penetrate through the bark into the xylem by 3-4 fen.
8. Stacking for colonization: Stacking is to maintain suitable temperature and humidity so that mycelium quickly germinates, colonizes, grows, and develops within the fungus logs. This is an important step for successful inoculation. The method is: first choose a stacking site, clear weeds, sprinkle a little insecticide or bleaching powder, rake it into the soil, then lay the inoculated fungus logs flat and pile them up into a "well" shape or "fish-back" shape, with a pile height of 3 chi. Then cover tightly with plastic film, press the edges with soil, and scatter a ring of insecticide around to prevent ants from climbing the pile and eating the mycelium. The temperature inside the pile should be maintained between 22°C and 32°C, and humidity at 60%-70%. If the temperature is too high, lift the surrounding film to ventilate once and lower the temperature. Turn the pile about once every 10 days, that is, turn everything inside and out, top and bottom, comprehensively, so that the temperature and humidity of the fungus logs in the pile remain even. The first turning does not require watering; after that, water once with each turning. If it can receive rainwater, even better. Colonization is complete in about 1 month.
9. Unstacking and arranging: After the fungus logs have been stacked for colonization and the mycelium has grown out of the logs, they can be unstacked and arranged. The purpose of arranging is to let the fungus logs absorb moisture from the ground, receive natural sunlight, rain, dew, and fresh air, change their living environment, let them quickly adapt to nature, promote further rapid spread of mycelium within the logs, and shift from the growth stage to the development stage. The method of arranging is to lay the fungus logs flat on the ground, with the whole body touching the ground and not elevated, with a spacing of 2 fingers between each. The site should preferably have some slope, to avoid rainwater accumulating on the ground and flooding the fungus logs. Turn the logs about once every 10 days, that is, turn the side originally touching the ground upward and the side originally facing up downward to touch the ground, so that the logs absorb moisture evenly and avoid infection by moisture-loving foreign fungi. In about 1 month, fungus buds will sprout abundantly, and then they can be racked.
10. Racking management: When fungus buds cover the logs, it indicates that the growth and development of the mycelium has entered the fruiting stage. At this time, external conditions of "alternating dry and wet" are needed. Racking can satisfy this need and reduce foreign fungi and pests that are not adapted to such conditions. The racking method is to use a long pole as a crossbeam, support both ends with forked tree branches, then lean the fungus logs diagonally against the crossbeam to form a "person" shape, with a spacing of 2 cun between each log. Each rack is calculated at 50 logs for yield. Management work after racking is very important. As the saying goes, "three parts planting, seven parts management," and "whether there is a harvest depends on planting, how much is harvested depends on management," which shows the importance of management work. Management work mainly includes removing long grass, foreign fungi, and pests, and regulating temperature, humidity, air, and light. At noon in summer, try to avoid strong direct sunlight on the fungus racks. In winter, the logs that have just started fruiting should be laid down to absorb moisture from the ground and keep warm, promoting early budding and early fruiting the following year.
11. Harvesting and sun-drying: After the wood ear fungus grows up, it should be harvested frequently and carefully selected to ensure a bumper harvest. For spring and autumn fungus, pick the large ones and leave the small ones, letting the small ones grow before picking. For summer fungus, pick large and small together, because summer temperatures are high, pests are many, and bacteria reproduce quickly, which can cause mature fungus to be eaten by insects or rot. The best time to pick is after rain when the sky clears and the fungus edges curl in, or in the morning while dew has not dried and the fungus is soft and moist. After harvesting, spread them thinly on drying mats and dry them in one go under strong sunlight. Do not turn them too much during drying to avoid forming curled ears. If there is continuous rainy weather, first adopt the method of rushing to harvest and pick, spread the harvested wet fungus flat on dry thatch or dry wood ear fungus to let the dry thatch or dry fungus absorb part of the moisture, and after the weather clears, move them out to dry together. If you cannot harvest them all in time, use plastic film to cover the fungus racks so that the already-grown wood ear fungus does not continue to be rained on and absorb water, causing log flow loss.
Substitute Material Cultivation
The continuous innovation of black fungus cultivation techniques has greatly increased both unit yield and total output, but it still cannot meet the needs of foreign trade export and the people's growing demand. With the promotion and development of artificial cultivation techniques, experimental research on new substitute material cultivation of wood ear fungus has been further promoted. At present, plastic bag cultivation is the main method, and the method is as follows:
1. Production process: about 40 days of spawn (plastic bag) after inoculation, about 2 months → cultivation bag (plastic bag) hole opening → 7-10 days fungus bud formation → 15-20 days mature harvest → 10 days second fungus bud formation → 15-20 days mature harvest → 10 days third fungus bud formation → 15-20 days harvest.
2. Selection of excellent spawn
The spawn for cultivating black fungus is domesticated and screened from the spawn used for log cultivation of black fungus, so not all spawn suitable for log cultivation can be used as spawn for substitute material cultivation. The suitable spawn age for cultivation spawn is 30-45 days. Such cultivation spawn has strong vitality, can reduce contamination by foreign fungi during the culture process, and can also enhance resistance to mold during cultivation. Generally, choose those with fast mycelial growth, thick and strong growth, quick colonization after inoculation; short production cycle, high yield, large caps, thick flesh, and deep color as spawn.
3. Cultivation season: In Shaanxi and several nearby provinces, using natural temperature, two crops can be grown per year. In spring, start making stock spawn in early January, make cultivation spawn in early February, make cultivation bags in mid-March, and produce fungus in April, May, and June. In autumn, make cultivation bags in mid-August, and produce fungus in September, October, and November.
Cultivation Methods
1. Formulas
Many agricultural and forestry product by-products can be used to cultivate black fungus. Several culture medium formulas are introduced below:
① Sawdust medium formula: sawdust (broadleaf tree) 78%, wheat bran (or rice bran) 20%, gypsum powder 1%, white sugar 1%, water about 65%.
② Cottonseed hull medium formula: cottonseed hull 90%, wheat bran (or rice bran) 8%, gypsum powder 1%, white sugar 1%, water about 65%.
③ Corn cob medium formula: corn cob (crushed into granules the size of soybeans) 70%-80%, sawdust (broadleaf tree) 10%-20%, wheat bran (or rice bran) 8%, gypsum powder 1%, white sugar 1%, water about 65%.
④ Rice straw medium formula: rice straw (fresh rice straw crushed or cut into small pieces) 75%, wheat bran (or rice bran) 15%, sawdust (broadleaf tree) 8%, gypsum powder 1%, white sugar 1%, water about 65%.
If conditions permit, adding 2% soybean powder to the above media is even better.
2. Mixing and bagging: Weigh the above culture materials in proportion, mix well, dissolve the sugar in water and pour it into the culture material, add water and stir, making the moisture content of the culture material reach about 65%. Or add water until, when the culture material is squeezed in the hand, water seeps out but does not drip. Then pile the material up and let it sit for 30-60 minutes, so that the material fully absorbs the sugar water, and bag immediately. There are three bagging methods, each with advantages and disadvantages, and you can choose according to circumstances.
The first method: choose plastic bags about 5 micrometers thick, with bag size about 17 cm x 33 cm and a square bottom. If you buy flat-bottom bags (the same as food bags), before bagging, first fold the two bottom corners inward until the two corners touch, so that after filling with culture material, the bag stands stable and can be placed directly on the cultivation rack. When bagging, put the already-mixed material into the bag, and while filling, shake forcefully on a smooth surface to make the culture material dense and uniformly tight from top to bottom. At this time, the height of the culture material is about 3/5 of the bag height. Wipe off the residual culture material on the upper part of the bag with a dry gauze, add a plastic neck ring (inner diameter 34 cm, height 3 cm), fold the plastic bag opening downward, tie tightly with a rubber band, making the shape like a glass bottle mouth, and insert a cotton plug.
The second method: choose tubular polypropylene plastic bags with a diameter of 13 cm, cut to a length of 35 cm, tie one end tightly with cotton thread, then melt the film with candle fire or an alcohol lamp flame to seal the bag opening. Put the culture material into the bag from the open end, shaking on the material pile while filling, or pressing firmly with fingers, until filled to 5 cm from the bag opening. Then twist the remaining plastic bag together, tie tightly with cotton thread, and melt the film to seal under candle fire or alcohol lamp flame. On a smooth tabletop, press the bag flat with your hand. Then use a 2 cm diameter hole puncher to punch a hole 2 cm in diameter and 1.5 cm deep on one side of the bag every 10 cm. Use scissors to cut the prepared medicinal adhesive tape into 3-4 cm squares; stick them over the holes. To facilitate operation during inoculation, roll up one corner of the adhesive tape into a double layer.
The third method: choose cylindrical polypropylene plastic bags with a diameter of 13 cm, tie one end with string, put the culture material into the bag from the other end, press the material firmly with your hand, until the material is filled to 5 cm from the bag opening, then gather the remaining plastic bag, tie with string, and inoculate from both ends afterward.
Note: Regardless of which bagging method is used, it must be done that the material is mixed, bagged, and sterilized on the same day.
Sterilization and Inoculation
Place the filled cultivation bags in an autoclave for sterilization, maintaining 1.5-2 hours at a pressure of 15 kg/cm2. When the pressure gauge drops to zero, take the bags out while hot and immediately place them in an inoculation box or inoculation room. If using a normal-pressure sterilization stove, maintain 6-8 hours, wait until the bag temperature drops to 30°C, or fumigate with potassium permanganate and formaldehyde for 30-40 minutes to disinfect the inoculation box or inoculation room space. When inoculating, note that continuous inoculation should not last too long, to avoid the temperature inside the box becoming too high (exceeding 40°C); the inoculation amount should be larger, which can shorten the time for mycelium to cover the surface and reduce chances of foreign fungus infection. As mentioned earlier, black fungus has relatively weak resistance to mold, especially Trichoderma, so sterilization must be thorough, and inoculation must be carried out under sterile operation to improve the finished product rate.
Mycelium Culture
During the entire process of mycelium culture, conditions should be created that allow healthy mycelial growth while also controlling the formation of black fungus fruiting bodies on the stick. Among all conditions, temperature is the most important factor. The optimal temperature for the culture room is 22°C-25°C. Since the temperature of the culture material inside the bag is often 2°C-3°C higher than room temperature, the culture room temperature should not exceed 25°C. Especially in the later stage of culture (that is, when mycelium has grown to more than about 1/2 the height of the culture material), if the temperature exceeds 25°C, yellow water will appear in the bag, and the water color will change from light to dark and from thin to sticky. The production of this sticky liquid easily promotes mold infection. The relative humidity of the culture room should be 50%-70%. If humidity is too low, the culture material loses too much water and dries out, which is unfavorable for mycelial growth. If relative humidity exceeds 70%, mold will grow on the cotton plug. Light can induce mycelium to twist and form primordia. In order to control the culture stage so that mycelium does not form fruiting body primordia, the culture room should remain dark or with extremely weak light intensity. Scatter some quicklime around the culture room to make it an alkaline environment and reduce chances of mold reproduction. When cultivation bags are placed on culture racks or piled on the ground for mycelium culture, they should not be turned too much. Because the volume of the plastic bag is not fixed, the volume changes where the hand pinches, squeezing air out of the bag. When the hand is removed, the volume returns, and a small amount of air enters. In this way, foreign fungus spores may enter. In addition, where the hand contacts the bag wall, pressure between the plastic bag and the culture material is increased. When encountering relatively sharp culture material (sawdust, cottonseed hulls), tiny holes invisible to the naked eye will be pricked, and foreign fungus spores will also enter from here, increasing the infection rate. Therefore, during the culture process, move them as little as possible. When checking for foreign fungi, be sure to handle them gently and place them down gently. If foreign fungi are found, take them out promptly and place them in a cooler place for continued observation. If the contamination level is relatively light, inject formaldehyde solution into the contaminated area and stick a small piece of adhesive tape over the needle hole to control continued spread of the foreign fungus.
Hole Opening
When the black fungus mycelium has covered the bag, move the fungus bags from the culture room to the cultivation room, remove the cotton plug and plastic neck ring, tie the bag opening tightly with string; or peel off the adhesive tape; prepare two basins of 5% limewater, first soak and wash the bags in one basin, then take them out. Use a blade to cut small openings around the bag, with spacing of 5-6 cm between two holes, length 1-1.5 cm, and depth reaching 0.3 cm into the material. You may also first open holes on one side of the fungus bag. Soak the opened fungus bags in the other basin of limewater, so that the hole openings are in an alkaline environment, which can effectively prevent foreign fungus damage.
Management During the Fruiting Period
The fungus bags after hole opening can be placed flat on the fungus bed racks in the cultivation room, or hung on seedling bed racks or tree branches in the forest, or placed on the ground covered with wet sand, and then conditions for the formation of black fungus fruiting body primordia should be created. First, increase the relative humidity of the cultivation environment to 90%-95%, and keep room temperature as much as possible at 20°C-25°C. Good ventilation and relatively strong scattered light are also indispensable conditions for the formation of black fungus primordia. The mycelium at the hole openings can receive relatively sufficient light, air, and humidity, effectively promoting the formation of fruiting bodies there. Therefore, when black fungus is cultivated by hole opening, the fruiting bodies all form at the hole openings or at ruptures in the plastic bag. This is the so-called "directional fruiting." Under suitable temperature, humidity, ventilation, and light conditions, generally 7-12 days after hole opening, many small black dots can be seen with the naked eye at the hole openings; they gradually grow larger and connect into a fungus bud (young fruiting body). At this time, more water is needed, a temperature of 15°C-25°C, relatively strong scattered light, and good ventilation. If continuous rainy weather occurs, the cultivation bags that have already formed fungus buds can be hung in the open air, where temperature, humidity, light, and air can all be fully satisfied, and the fungus buds develop faster. At this time, if green mold or orange-red Neurospora contamination is found at the base of the fungus or on young small fungus caps, the fungus bags can be carefully rinsed under a faucet to wash away the foreign fungi, but do not wash away the fruiting bodies. Under suitable environmental conditions, about 10-15 days after the fungus buds form, the fungus caps flatten and the fruiting bodies mature, and they can be harvested.
Harvesting and Processing
The standard for black fungus maturity is when the fungus caps are fully expanded, begin to curl at the edges, the fungus base becomes thinner, and the color changes from black to brown; then they can be picked. Harvest frequently and carefully, picking the large ones and leaving the small ones, so as not to cause fungus flow. Mature fungus left unpicked on the fungus bag is susceptible to pests, diseases, or fungus flow. When harvesting, use a small knife to shave flat against the bag wall. The harvested wood ear fungus should be sun-dried or oven-dried promptly. The drying temperature should not exceed 50°C; if the temperature is too high, the wood ear fungus will stick together into lumps and affect quality. After the wood ear fungus is dry, package and store promptly to prevent mildew or insect damage. After harvesting, stop direct water spraying on the fungus bags for four to five days, allowing the mycelium to accumulate nutrients. After about 10 days, the second batch of fungus buds forms, repeat the above management, and two more harvests can be obtained.