Key Technical Points for Over-summering Management of Semi-cooked Substrate Cultivation of Nameko Mushrooms

In the Dandong area, from mid-June each year, the weather shifts from dry and muggy to the continuous rain season, with persistent drizzle and no adequate sunlight for more than 10 days, high temperatures and high humidity, resembling "sauna" weather. From mid-July until the opening of the beds, there is again scorching sun, and the spawn bags in a high-temperature, high-humidity environment are highly prone to spawn degeneration or invasion by pests and diseases, causing the spawn beds (bags) to become soft and rotten after opening or after the first watering, resulting in varying degrees of economic loss for mushroom growers. Based on our cultivation practice in recent years, we have mastered a set of over-summering management methods. The key management points are introduced as follows:

1. Carry out good spawn-running management before over-summering

Select superior spawn. The cultivation time must be appropriate. Place the spawn beds (bags) indoors or outdoors in shaded stacks for spawn running, turn the stacks at regular intervals, and once the mycelium has covered the surface of the spawn beds (bags), promptly place them on the growing shelves. Spawn beds (bags) contaminated by foreign microorganisms should be placed on the lowest level of the growing shelves, using the low-temperature environment to suppress the growth of contaminants, and those with severe contamination should be discarded promptly. When the beds (bags) change from their original white color to orange-red, this indicates that the mycelial skin layer has fully formed, and over-summering management can begin.

2. Over-summering management

2.1 Cooling

Nameko mushroom is a low-temperature fruiting edible fungus. If temperature control measures for the spawn beds (bags) during over-summering are inappropriate, the vitality of the mycelium will decline, its metabolism will become disordered, and it will gradually die. This is one of the main causes of the spawn beds becoming soft after opening, the death of the mycelium, and what growers call "empty bag disease." The main methods to prevent this disease: when building the mushroom shed, the center of the shed should be no less than 3.5 m from the ground, and the top layer of spawn beds should be 0.8-1.0 m from the shed roof. Cover the shed roof with crop straw or thickened straw mats to avoid direct sunlight on the spawn beds. Vine plants can also be grown on both sides of the shed, letting their branches and leaves shade the shed and lower the temperature for over-summering. The temperature inside the shed should be kept within 30°C; if it exceeds 30°C, promptly sprinkle water on the ground around the inside of the shed and on the shed roof, and strengthen ventilation to cool it down.

2.2 Avoiding light

The over-summering site requires shading and weak light, and direct sunlight is strictly prohibited. Because in the later stage of spawn running the mycelium penetrates the entire substrate, and an orange-yellow waxy layer forms on the surface of the spawn beds (bags). If scattered light is too strong, the waxy layer thickens, water cannot easily enter the substrate, fruiting body formation becomes difficult, and it can also cause the bed spawn (bags) to dry out and die due to rapid water evaporation. Therefore, the shading material at the bottom and around the shed must be thickened.

2.3 Reducing humidity

The relative air humidity must not exceed 80%. If the humidity is too high, the mycelial skin thickens and the spawn beds (bags) are prone to molding and rotting, and at the same time the spawn beds (bags) are also vulnerable to pest damage. In summer there are many high-temperature, high-humidity days, causing mushroom flies, mushroom mosquitoes, slugs and others to multiply in large numbers, biting and eating the Nameko mycelium. Large amounts of mycelium inside the spawn beds (bags) are eaten, the spawn beds become loose, and they rot quickly after watering. The main humidity-reducing measures are strengthening ventilation; in addition, spread quicklime or fresh coal cinders and other moisture-absorbing materials on the ground, and promptly drain any accumulated water inside the spawn beds (bags).

2.4 Ventilation

Keep the air inside the shed fresh and circulating at all times, ventilating 2-4 times per day. If the temperature inside the shed is above 25°C, doors and windows must be opened day and night for ventilation and cooling. Without ventilation for a long time, the temperature will rise and the humidity will also increase correspondingly, becoming a breeding ground for various pests and diseases.

2.5 Pest and disease control

Regularly spray the entire interior space of the shed with 2% limewater, then spray with a 1000-fold dilution of thiophanate-methyl, and the next day spray once more with a 200-fold dilution of dichlorvos or a 500-fold dilution of 90% trichlorfon. Comprehensive treatment twice during the entire over-summering period can achieve relatively good control results.

2.6 Other situations

2.6.1 When individual spawn beds (bags) fruit in summer, in mild cases the beds should not be opened; instead, cut the film at the fruiting site, remove the mushroom buds, and then seal it well with tape. When fruiting heavily, the spawn beds can be opened and normal water management carried out; the harvested fruiting bodies can be sold fresh on the market or processed by salting

2.6.2 From the late over-summering period to 1 week before opening the beds, the day-night temperature difference inside the mushroom shed should be appropriately adjusted to induce primordium formation. At night, roll up the plastic around the mushroom shed, and cover it during the day, repeating for several days, to prompt the Nameko mycelium to shift from the vegetative growth stage to the reproductive growth stage.