Cultivation of Agaricus bisporus, the "World Mushroom," and the Causes of and Countermeasures for Fruiting Disorders

Agaricus bisporus, also known as the white mushroom, button mushroom, or cultivated mushroom, is a mushroom species cultivated and consumed worldwide, known as the “World Mushroom,” and can be sold fresh, canned, or salted. At present, it is developing very rapidly, growing at a rate of 15%-20% each year. So how do you grow Agaricus bisporus? What are the causes of and countermeasures for fruiting disorders?

I. How do you grow Agaricus bisporus?

1. Sowing

Begin sowing when the temperature drops below 27°C. Generally, broadcast sowing is used: evenly scatter 3/4 of the spawn amount over the surface of the substrate, insert a small fork into half the depth of the substrate, and shake gently so that the spawn is evenly distributed into the substrate, then evenly scatter the remaining 1/4 of the spawn over the surface. After sowing, cover with a layer of newspaper; if the temperature inside the shed is relatively high and the insulation performance is good, the newspaper may be omitted.

2. Mycelial running

From sowing to casing is the mycelial running stage. During this period, the temperature should be controlled at 20-25°C and the relative air humidity kept at around 70%. For 1-2 days after sowing, generally keep it closed without ventilation, focusing on heat and moisture retention. After about 3 days, the mycelium begins to germinate; at this point, ventilation should be increased so that the mycelium on the surface grows into the substrate. When the mushroom shed is dry, water may be sprinkled into the air, onto the walls, and along the walkways to increase air humidity.

3. Treatment of casing material

Ideal casing materials generally include paddy field soil, pond soil, wheat field soil, soybean field soil, yellow soil, river mud, etc. Vegetable garden soil is generally not used, because its high nitrogen content easily causes excessive mycelial growth, fewer mushrooms, and it easily harbors large amounts of pathogens and insect eggs. Soil should be taken from below 15 cm of the surface, exposed to the scorching sun, and preferably in granular form: small particles 0.5-0.8 cm, clods 1.5-2.0 cm. Then mix in 1% lime powder, spray with formaldehyde and 0.05% dichlorvos, pile it up, cover with plastic film, and let it sit for 1 day. Then remove the film, spread the pile out to let the chemical odor dissipate completely, and it is ready for casing.

4. Casing

After about 15 days, when the mycelium has basically grown through 2/3 of the substrate, casing should be done promptly. After casing, use 3 days to spray water so that the casing soil fully absorbs water, but the water must not seep into the substrate. When spraying, do it frequently, lightly, and in small amounts. The thickness of the casing layer is 25-30 cm.

5. Fruiting management

After casing, fruiting begins in about 20 days. Keep the temperature at 20-24°C and the relative air humidity at 80%-85%. During this period, generally do not spray water onto the substrate surface; if too wet, aeration is poor and the mycelium struggles to penetrate the soil layer; if too dry, the mycelium becomes sparse. Maintain suitable temperature and humidity, and the mycelium will quickly grow white and vigorous. When the mycelium covers the substrate surface, spray heavy water to make the mycelium lie down; this watering is also called “fruiting water,” to stimulate the formation of fruiting bodies. After that, stop watering for 2-3 days while increasing ventilation. When the mycelium twists into small white dots, begin spraying water and increase humidity. Keep the relative air humidity at around 90% and control the temperature at 12-18°C. As the number of mushrooms increases and the fruiting bodies develop, increase the amount of water sprayed. When spraying, increase ventilation; do not spray at high temperatures, and do not spray before harvesting.

When the mushrooms grow to the size of a soybean (4458, -23.00, -0.51%), spray 1-2 relatively heavy rounds of “fruiting water,” once a day, to promote the growth of young mushrooms. After that, stop watering for 2 days, then gradually reduce the amount of water sprayed as the mushrooms grow, maintaining this until just before the peak of the fruiting flush, and then gradually reduce the amount of water sprayed as the mushrooms are harvested. Note that when spraying, do it frequently, lightly, and finely; spray less on cloudy days and not at all on rainy days. During the fruiting stage, harvest every day, picking according to the size required by the market, but the caps must not open. When harvesting, twist gently and try not to pull out the growing substrate. Trim off the muddy base of the stem immediately after picking to prevent loss of commercial value. Handle gently, as bruised areas discolor very easily. After each flush is harvested, clean the substrate surface, fill the hollows left by harvested mushrooms with soil, and keep the substrate surface level and clean. After finishing, spray once more with 1% lime water, then manage as usual; the second batch of mushrooms appears in about 7-10 days. Generally, 6-9 flushes are harvested. After 3 flushes are harvested, loosen the soil layer and make holes to improve aeration within the substrate, and after harvesting and before new pins grow to the size of a bean, apply fertilizer.

II. What are the fruiting disorders of Agaricus bisporus and their countermeasures?

1. Stunted mycelial growth after sowing

After inoculation, the mycelium grows poorly, shown by the spawn failing to germinate, failing to colonize the substrate, mycelium growing only on the surface, or shrinkage.

The main causes are improper temperature and humidity in the mushroom house and poor ventilation.

Solution: when the temperature in the mushroom house is relatively high, take cooling measures to bring it to 22-25°C; if the substrate surface appears somewhat dry, promptly spray 0.3% superphosphate or potassium dihydrogen phosphate solution; if the substrate surface is too wet, increase ventilation in the mushroom house; if there is an ammonia smell in the mushroom house, increase ventilation and poke holes in the substrate surface to release ammonia gas.

2. Excessive mycelial growth after casing

After sowing, the mycelium grows too vigorously and forms a dense, water-impermeable, air-impermeable “mycelial mat” on the substrate surface, mainly caused by high temperature and high humidity.

Solution: when the mycelium grows out of the casing layer, increase ventilation in the mushroom house and lower the temperature and humidity inside it; in the early morning and evening when temperatures are low, spray the substrate surface lightly and appropriately; when the mycelium forms a “mat,” promptly remove it with a small knife or bamboo strip.

3. Mycelial degeneration in the casing layer

3-5 days after casing, the mycelium does not grow onto the soil and appears grayish-white and weak; in severe cases, no mycelium is visible on the substrate surface or it turns black. This is mainly caused by excessive watering after casing, resulting in oxygen deprivation and shrinkage of the mycelium.

Solution: stop watering and increase ventilation.

4. Dead mushrooms

During the fruiting period, mushrooms in patches or an entire flush wilt and turn yellow, stop growing, and finally die.

The main causes are: temperature too high, causing nutrients in the fruiting body to flow backward; mycelium growing too fast and fruiting too densely, so nutrition cannot be supplied; carbon dioxide content in the mushroom house too high and oxygen insufficient; temperature in the mushroom shed too high (above 20°C) and humidity too high (above 95%), with no timely ventilation after watering, causing water accumulation in the mushroom bed and oxygen deficiency.

Solution: inoculate an appropriate amount to avoid excessively vigorous mycelial growth and overly dense fruiting, which causes nutrient deficiency; do not let the water content of the casing layer be too high; after watering to cool down, ventilate promptly to avoid water accumulation on the surface of the mushroom bed.

5. Hollow white-stem mushrooms

The mushroom stem becomes loose and white, and even shrinks to form a hollow center.

The main causes are: during the fruiting body growth stage, dry air (humidity below 85%) and high temperature (above 18°C).

Solution: spray promptly during the day to keep the relative air humidity at 90%; after watering in the early morning and evening, ventilate promptly; keep the temperature in the mushroom shed at 14-18°C.

6. Premature opening of the cap

The cap opens too early, resulting in poor commercial quality.

Main causes: a sudden low temperature at the early fruiting stage, a large temperature difference, and relatively low humidity in the mushroom house.

7. Scaly mushrooms

The cap cracks and forms scales.

Main causes: the air temperature in the mushroom house is below 14°C, humidity is below 80%, and the temperature difference and wet-dry difference are too large.

Solution: strengthen insulation measures and avoid cold wind.

8. Fruiting bodies fail to differentiate

There are mushroom buds but the fruiting bodies do not differentiate, and no cap or stem forms; only a mycelial mass forms.

Main causes: suitable environmental conditions in the early stage of fruiting body growth but unsuitable conditions in the later stage; improper use of pesticides (such as excessive or indiscriminate application).

Solution: master the temperature and humidity of the mushroom house and strengthen ventilation; do a good job of disinfecting the mushroom house and the surrounding environmental sanitation to avoid pests and diseases; use pesticides reasonably.

9. Rust-spotted mushrooms

After the fruiting bodies emerge, brown rust-like spots appear on the cap surface, affecting the quality of Agaricus bisporus.

Main causes: no timely ventilation after watering, excessive air humidity in the mushroom house, and water droplets remaining on the surface of the fruiting bodies for a long time.

Solution: keep the air in the mushroom house fresh at all times, and ventilate promptly after watering to disperse moisture.