Edible mushroom disease prevention and control methods: strict contamination prevention when culturing spawn

During the culture of edible mushroom spawn, contamination by various foreign microorganisms such as green mold, blue mold, Aspergillus, Rhizopus, Mucor and bacteria occurs to varying degrees, and is especially serious in hot seasons. In production, the invasion of these foreign microorganisms often causes reduced yields or even total crop failure. Therefore, finding the causes of foreign microorganism contamination is of great significance for improving cultivation success rates and increasing economic returns. Under normal conditions, the contamination rate of secondary and tertiary spawn is below 5%. If it exceeds this range, we need to investigate the causes. The causes of spawn contamination are as follows:

1. Incomplete sterilization: Incomplete sterilization of the growing medium will cause foreign microorganism contamination, and contamination typically appears within 3-5 days. Incomplete sterilization is also caused by the following several reasons:

① Improper sterilization operation: Generally, the mycelium and spores of foreign microorganisms can be killed by atmospheric pressure at 100°C for 6-8 hours or at 121°C for 0.5-2 hours. At present, edible mushroom growing media are often sterilized by atmospheric pressure sterilization or high-pressure sterilization. Atmospheric pressure sterilization is more difficult for materials such as grain and manure-straw, and it is not easy to completely achieve the sterilization effect; high-pressure sterilization is much more effective.

② Influence of the nature of the growing medium: The type of material required for spawn production, the microbial load in the growing medium, the moisture content and the pH can all affect the sterilization effect. When sterilizing, the corresponding sterilization time should be selected according to the different growing medium formulas.

③ Improper stacking of spawn bottles (bags): The way spawn bottles (bags) are stacked in the sterilization pot can affect the sterilization effect. Certain gaps should be left during arrangement to allow steam circulation and temperature rise. When sterilizing growing medium in spawn bags, because plastic bags are prone to deformation and softening after heating, if the filling is not tight, the gaps between the spawn bags will be reduced when stacked and pressed together, affecting the sterilization effect.

④ Influence of spawn bottles or spawn bags: During spawn production, spawn bottles or spawn bags are generally used. Plastic bags conduct heat quickly, while glass bottles conduct heat slowly. With the same growing medium and the same sterilization method, bottled medium requires a slightly longer sterilization time than bagged medium. In addition, individual containers that are not tightly sealed or have small cracks can also lead to foreign microorganism contamination.

2. Non-standard inoculation operations: The edible mushroom inoculation process requires strict aseptic operation. If the operation is not standardized, it is very easy to cause foreign microorganism contamination of the growing medium. The contaminating microorganisms are generally foreign microorganisms in the air of the inoculation room, on the surface of the spawn bags, and on the body surface of the inoculation personnel. The characteristic of growing medium contamination caused by non-standard operations is that the foreign microorganisms grow on the surface of the growing medium, generally occurring at the opening of the spawn bag and at the inoculation site. Therefore, aseptic operating procedures must be strictly followed, and the inoculation room must be strictly disinfected with a special disinfectant for mushroom rooms.

3. Spawn carrying foreign microorganisms: The stock spawn used for expanded culture must itself be pure, so as to ensure the uniformity of the spawn. If the spawn itself is not pure, it can cause contamination on a batch scale. In a batch of spawn in production, the spawn gathered together all show contamination, and the contaminated area is at the spawn block, with contamination appearing relatively early, within 3-5 days after inoculation. Therefore, when producing spawn, we should try to use excellent stock spawn with strong vitality, suitable spawn age and strong stress resistance.

4. Unclean culture room: An unclean growing medium, poor air circulation and a humid room can also lead to infection by foreign microorganisms. In this case, the contamination rate is relatively low, but as the culture time is extended, the contamination rate will gradually increase. A large amount of contamination appears relatively late, generally appearing 10 days after inoculation.