Management Techniques for the Color-Turning Stage of Block-Cultivated Shiitake Mushrooms

Semi-cooked shiitake block cultivation; whether the color turning of the mushroom blocks is good or poor directly affects yield and quality. The color-turned layer of shiitake plays a role similar to tree bark. After color turning, it can be divided into 4 types, namely brownish-red, dark brown, light brown and grayish-white. Brownish-red is the most ideal; it represents mushroom blocks with appropriately sparse and dense fruiting, uniformity and consistency, high yield and good quality. Dark brown indicates that the mushroom skin is relatively thick, fruiting is late, individual mushrooms are larger, and yield is low. Light brown indicates that the mushroom skin is relatively thin, fruiting is earlier and concentrated, deformed mushrooms are numerous, mushrooms are small, caps open easily, and yield is low. Grayish-white mushroom blocks can produce a few signal mushrooms, and when soaked in water the mushroom blocks will loosen and break apart, with basically no yield. In Northeast China, block-cultivated shiitake generally enters the color-turning stage in early May. The overall principle during the color-turning period is that the mycelium should grow robustly, not grow excessively, the mushroom skin formed on the blocks should be appropriately thin or thick, and ultimately turn into the ideal brownish-red outer layer.

1. Temperature management. About 25 days after the shiitake is pressed into blocks, the mycelium reaches physiological maturity, and at this time the first ventilation of the mushroom blocks begins. After ventilation, the mycelium on the mushroom blocks grows rapidly and becomes thick and strong. When the mycelium on the surface of the mushroom blocks is dense and white, the culture material particles can no longer be seen, and scattered brown color-turning spots appear on the mushroom blocks in the bag, open the plastic bag promptly, spread the plastic flat on the cultivation rack, then place the mushroom blocks on the plastic, and finally cover with a layer of plastic. At this time, promptly raise the ambient temperature of the mushroom house, controlling it at 18-22°C during the day, and at night, in combination with opening windows for ventilation, it is best to lower the temperature below 10°C to create a relatively large temperature difference. At this time the mushroom blocks will show water exudation, first exuding white water, and later the exuded water gradually deepens in color and becomes dark brown; at this time, wipe off the water promptly.

2. Humidity management. Promptly increase the difference between dry and wet conditions on the surface of the mushroom blocks to promote the timely lodging of the mycelium. Lift, shake and cover the film multiple times. Ventilate once each morning and evening, 20-3 minutes each time.

3. Light. At this time, increase the scattered light in the mushroom house to force the mycelium on the mushroom blocks to gradually lodge. If after adopting the above measures the mycelium lodges slowly, combine this with extending the ventilation time and ventilate at noon each day when the air is dry and light intensity is high. After the surface humidity of the mushroom blocks decreases and the mycelium lodges, do not lift the covering film for 3-4 days, and ensure normal ventilation in the mushroom house. After such management, in about 20 days the mushroom blocks can basically smoothly turn into a glossy brownish-red. Only mushroom blocks with this kind of brownish-red color-turned layer can produce mushrooms that are uniform and consistent, with large fruiting bodies, obvious flushes, and high yield, achieving the goal of high and abundant yield. Shiitake is a typical temperature-changing fruiting fungus; after color turning, the greater the temperature difference, the more mushrooms are produced, the higher the yield, and the better the benefits.