What to Do When Shiitake Mushroom Logs Rot? Detailed Analysis of Causes and Control Techniques
In recent years, varying degrees of log rot have appeared in some shiitake-producing areas, causing waste of resources and economic losses for mushroom growers, and in some areas it has seriously threatened the development of the shiitake industry. For example, in Xianliang Town, Qingyuan County, Zhejiang Province, the log rot rate in 1999 reached 17%, with some individual growers exceeding 50%, resulting in heavy losses. In response, we have conducted dedicated research since 1999 and have preliminarily identified the causes of rot and control techniques.
1. Causes of log rot
Log rot mostly occurs in old mushroom-producing areas with many years of cultivation. Its fundamental cause is invasion and infection by competitive contaminant microorganisms, so all factors that trigger invasion and infection by contaminant microorganisms can lead to log rot. Summarized, there are the following aspects.
(1) Reduced stress resistance of cultivated varieties. Reduced stress resistance is a manifestation of variety degeneration, and this is the internal cause of log rot.
In old mushroom-producing areas, some leading varieties have been planted for many years, their varietal traits have degenerated, mycelial vitality has weakened, their adaptability to the environment is poor, and their ability to resist invasion by contaminant microorganisms has declined, so competitive contaminant microorganisms can take advantage of the weakness and cause log rot. For example, the shiitake variety 241-4, because it has been cultivated for many years, has shown obvious declines in yield and stress resistance in recent years, and its logs are also prone to rot.
(2) Harsh cultivation environment. A harsh cultivation environment hinders mycelial growth, weakens stress resistance, or causes aging, death, and autolysis, thereby causing log rot. Factors such as high summer temperatures, poor ventilation, improper use of disinfectants, and deteriorated raw materials can also induce rot.
(3) Damage by insect pests. Mushroom pests enter the logs through ventilation holes to grow and reproduce, directly biting and feeding on the mycelium. After the mycelium is injured, a local environment of high temperature and high nutrients forms, allowing competitive contaminant microorganisms to invade and infect, resulting in cross-infection by insects and microorganisms and leading to log rot. In old mushroom-producing areas, insect population density is high and damage is severe, so log rot is relatively more serious.
(4) Damage from piercing holes. During cultivation, if the operation of piercing holes for ventilation is improper, the piercing tool (iron nail, bamboo skewer, etc.) directly injures the mycelium, leading to invasion and infection by contaminant microorganisms and causing rot.
(5) Damage from pesticide injury. Shiitake mycelium or fruiting bodies are very sensitive to most pesticides and are prone to pesticide injury. For example, dichlorvos, dimethoate, and others have obvious toxic effects on mycelium. When mushroom growers use these pesticides for insect control, the result, although aimed at pests, causes log rot.
2. Control of log rot
The control of log rot should focus on prevention, with treatment as a supplement, and should be carried out throughout the entire cultivation management process.
(1) Select excellent varieties, and purify and rejuvenate degenerated varieties.
(2) Carry out cultivation management strictly in accordance with the technical regulations for high-yield shiitake cultivation. ① Arrange varieties rationally. According to local climatic characteristics, choose suitable varieties. ② Do a good job of sanitation at the cultivation site and environment, and promptly clean up discarded logs from the previous year; old mushroom yards should be sprayed with fungicides and insecticides to reduce sources of contaminant microorganism contamination and lower insect population density. ③ Strictly control the amount of disinfectants used. At present, the active ingredients contained in disinfectants on the market are all the same, and the best dosage is 3-4 grams per cubic meter; never exceed 6 grams. ④ Seal inoculation openings with wax or tape to prevent insects and microorganisms from invading the logs through the inoculation openings. ⑤ Hole piercing for ventilation must be done in a standardized way; the diameter of the iron nail should be less than 2 mm, the hole depth should be 1-1.5 cm, holes should be pierced on sunny days, and holes should not be pierced at nodular areas. ⑥ Control insects and prevent diseases rationally. Use the high-efficiency, side-effect-free, non-toxic, long-lasting mushroom-specific insecticide "Guchongjing," spraying once after the first hole piercing and again two months later, which can effectively control insect pests. Never use insecticides such as dichlorvos that are unsuitable for use on shiitake.
(3) Treat rotten logs promptly. After discovering log rot, promptly pick out the rotten logs and stack them separately to avoid cross-infection among logs, and carry out the following treatment: ① Use a clean blade to cut off the rotten part, wipe the diseased spot, cut surface, and film with fungicides such as kemieling, then put the film back and seal it tightly with tape to prevent water loss and re-invasion by insects and microorganisms. This operation is best completed under aseptic conditions. ② For logs that begin to rot at the early stage of mycelial growth, resolutely carry out disinfection and inoculation again (redo).