Artificial inoculation methods for log cultivation of shiitake mushrooms

When the logs are sufficiently dried, inoculation should be carried out promptly. The inoculation time for shiitake is generally above 5°C and below 20°C, with a monthly average temperature of around 10°C being ideal. In the region south of the Yangtze River in China, inoculation of shiitake logs takes place from late February to early April, with the optimal period being from February to mid-March. There are sawdust spawn, stick spawn and wedge spawn; most log cultivation in China uses sawdust spawn. High-quality pure shiitake spawn has white and dense mycelium, the distinctive aroma of shiitake, aerial hyphae capable of climbing the container wall, and no discoloration or obvious inhibition lines in the substrate. In some relatively fast-growing strains, white primordia appear inside the bottle before the mycelium has reached the bottom; such spawn is generally a fast-growing, high-yielding strain. Any spawn with an excessively long spawn age, yellowed mycelium, shrunken or dark-brown substrate, or that has pulled away from the bottle wall should not be used.

The inoculation rate is generally 6-8 bottles of spawn per cubic meter of logs. Inoculation tools include electric drills, hole punches, inoculation axes, hand drills and belt punches. The inoculation method can be divided into three steps:

① Drilling inoculation holes: The inoculation holes are 1-1.2 cm in diameter and 1.2-1.5 cm deep. Between holes, the vertical spacing is generally 15-20 cm and the horizontal spacing 8-10 cm. At the two ends of the cross-section and at injured areas, the holes may be appropriately closer together to resist the invasion of contaminating microorganisms. Holes in adjacent rows should be staggered in a plum-blossom arrangement so that mushrooms emerge evenly. To improve the utilization rate of the mushroom logs, appropriate close planting must be carried out according to the thickness and material of the logs.

② Inoculation: After drilling the holes, the spawn should be inserted as quickly as possible to prevent the hole walls from drying out and contaminating microorganisms from invading. When inoculating, inoculate the small logs first, then the medium and large logs. If it is sawdust spawn, keep it in blocks as much as possible and gently fill it into the inoculation holes, filling them to about 80% full; if it is plug spawn, after placing it into the inoculation hole, press it in firmly so that the outer end of the plug is flush with the bark and will not fall out. Shiitake spawn should be used as soon as it is removed; it is best to use up the removed spawn the same day and not leave it overnight.

③ Covering the holes: When using sawdust spawn, after inoculation is completed, the pre-made bark covers (1.5-2 mm larger than the inoculation holes) should be placed over the holes and tapped tight and flat. The covers and the mushroom logs must be of the same tree species, 4-5 mm thick, to avoid falling off when exposed to heat or cold. Instead of bark covers, wax sealing may also be used. For plug spawn, no covers or wax sealing are needed.

Sawdust spawn is convenient to make, and the survival rate after inoculation can reach over 90%, whereas plug spawn, because part of it is exposed after inoculation, is prone to drying out and infection by contaminating microorganisms.