Alexander Tsarev
Mushroom industry

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Chemical treatment and disinfection

Technologists and team members of chemical treatment should remember that:

The use of disinfectants is an essential part of hygiene maintenance inside and around the farm. The disinfectants that are allowed to be used in mushroom production are used to disinfect surfaces and necessary materials. The contact action of a disinfectant with objects and its evaporation inside the room happens depending on the disinfectant used.

The disinfection of machinery, equipment etc. will be effective only when all materials are kept clean. To make the treatment really effective, its not only important to apply a necessary amount of disinfectant, but to provide a sufficient amount of time of its contact with the equipment. Disinfection and an immediate rinsing dont have any effect.

At using formaldehyde, its important to maintain the temperature above 16 C for its efficiency, and a high level of humidity is also desirable. At a temperature of 0 to 16ºC a positive effect is possible only at a contact action of formaldehyde which means only a limited disinfecting effect.

In case of using disinfectants, meant for contact action only, the contact must last for not less than 20 minutes. The disinfecting treatment for hygiene purposes has to be the following:

В случае использования дезинфицирующих средств, предназначенных только для контактного действия, время контакта должно быть не менее 20 минут. Необходимо обращать внимание на разницу применения разрешенных препаратов. Дезинфицирующая обработка в целях гигиены должна быть следующей:

  1. During spawn run.

    After the growing room is filled, the first treatment of the ceiling and walls of the growing room with 2% of formalin solution is carried out.

    The following treatment is carried out after 3-4 days with 0.5 % of formalin (150 ml of industrial (40%) formalin is dissolved in 30 l of water for 100 m²).

  2. Before the preparation of casing layer.

    Before the preparation of the casing mixture, a disinfection of cleaned floor, machinery and equipment with 2% of formalin solution is carried out (2 liters of industrial (40%) formalin are dissolved in 100 liters of water). The effect of this treatment is based on contact action. That is why the contact has to last for at least 20 minutes.

  3. After the preparation of casing layer.

    After preparation, the casing layer is treated with 0.5% of formalin, covered with a clean (disinfected) polyethylene film and kept for 24 hours.

    In the evening (8-10 hours) before the application of the casing layer, all machinery and equipment must be disinfected with 2% of formalin solution prepared by the team of loaders beforehand. Its very important to maintain the duration of contact of the disinfectant with the treated surface (not less than 20 minutes).

  4. After the application of casing layer.

    Right after the casing layer is applied, it is sprinkled with 2% formalin solution (2 liters of industrial 40% formalin are dissolved in 100 liters of water for 100 m²). This treatment added to the contact action might cause evaporation, and this is why the growing room is closed for 8-10 hours after treatment. Then, it is slightly ventilated. A contact action is necessary to destroy nematodes and Mycogone and Verticillium spores.

  5. The disinfection of machinery, tools and equipment.

    All equipment must be thoroughly cleaned right after utilization, and before further utilization, and disinfected with 2% of formalin solution. With this method of disinfection its very important to maintain the duration of the contact of not more than 20 minutes. The disinfectant must remain on the disinfected surface. Tools and equipment must be stored in separate, closed rooms.

  6. The disinfection of clean footwear.

    Footwear is disinfected with 2% of formalin solution or a special disinfectant for footwear, which is used to treat a mat in a special container before entering the room. The mats of all entrances and exits in clean and dirty corridors, compost preparation building and growing rooms are cleaned and treated with a disinfectant (2% of formalin solution).

    The mats can be treated with various chlorine-containing substances.

  7. The disinfection of the working corridors.

    This process can be carried out by sprinkling one liter of industrial formalin, stirred in 10 liters of water per 100 m³ of the rooms volume. The room must be closed for 8-10 hours after treatment and then ventilated (filter the air), before anybody enters. The floors and ceilings can also be treated with mortargrout.

  8. The disinfection of tunnels.

    When using tunnels to grow mycelium, they should be kept at a temperature of 70C for 6 hours after unloading. This thermal treatment is meant for disinfection, and especially for killing the spores of pathogenic molds. In order to maintain the temperature here, steam should be used. In this case, disinfection will be more effective.

    During pasteurization in the pasteurization tunnels a thermal treatment is also carried out.

    Underlying and drawing nets, and also the ventilation openings under the grate should be thoroughly cleaned after unloading. The remains of compost can serve as a nutrient medium for pathogenic molds and can become the reason for dirtying and/or blockage. As a result, the movement of air in the tunnel becomes uneven and it will be impossible to reach the desired temperature.

  9. Packaging.

    During harvesting, the crates contact spores (which can be infected by virus). After the mushrooms have been harvested, they remain in the crates for at least one day, depending on the sale, so, their bits remain in the crates, including spores (Which can carry a virus disease called dieback).

    Crates for mushroom harvesting are used many times, then it is possible for the virus disease to be transferred trough them. That is why it is important to use a disposable package, or crates and containers which can be cleaned and disinfected after use.

    Packing crates are cleaned and disinfected by special washing and disinfecting machines or by hand. The recommendations for the treatment of packing crates given here are based on the latest research.

    The washing and disinfecting machine consists of the following parts:

    1. Conveyer belt;
    2. A tank used to wet the containers;
    3. A tank for washing, where the temperature of 70C is maintained and a special detersive is added (K 500 0.3%). The cleaning solution must be changed everyday. Each packing crate must remain in this tank for not less than 23 seconds;
    4. A tank with cold water for rinsing and cooling the crates, where the remains of the detersive are washed away and the crates are cooled down to 23-25C. Cooling prevents undesirable rise in temperature in the disinfection tank;
    5. Disinfection tank with a chlorine solution (300-500 ppm). The concentration is measured automatically. The solution temperature must be about 23C, and mustnt exceed 25C, other ways the chlorine will evaporate very quickly. The crates should remain in this tank for at least 15 seconds;
    6. Unloading conveyer, by which the crates are lowered and the remains of the disinfecting liquid flow down.

    The dirty and clean parts of the washing and disinfecting machine must be separated from each other, like the tank for rinsing and cooling. The temperature, waiting time the solutions concentration must be maintained. The combination of waiting time, temperature and the concentration of chlorine will ensure the necessary disinfection. Its also very important to store solutions from various tanks separately, in order to escape a decrease in their efficiency. The disinfected crates must be stored in a separate room and delivered to the farm in a special or already disinfected transport.

  10. The storage and removal of organic materials.

    The stipes and dead mushrooms must be removed from the beds regularly. Diseases like green molds (species of Trichoderma), cobweb mold and bacteriosis can develop on the remaining stipes. Stipes, dead mushrooms and everything else must be collected into plastic bags or closed containers and regularly removed from the farm. Its also recommended to clean empty containers regularly and disinfect them with 2% formalin solution. At the same time, its important to get rid of all potential sources of infection rubbish dumps around the farm.

  11. Storing mycelium.

    Spores can be released in cold stores, where harvested (open) mushrooms are stored. Mushroom spores infected with a virus disease called dieback, can spread the infection. That is why storing mycelium and mushrooms in one cold store isnt hygienic. Its best to store mycelium separately. This aspect is important not only for those who produce compost fully grown with mycelium, but also for the farms that specialize in mushroom cultivation. If there are no separate cold stores, containers and bags with mycelium must be disinfected from the outer side before use (for example, using clean cloth soaked in hot water, a disinfectant or alcoholic solution).

  12. Steaming.

    Pathogenic organisms (spores, eggs, larvae) can develop in the substrate or on the stipes during mushroom growth. Mushroom spores that have been infected with a dieback virus can spread in the growing room, and virus affected mycelium can grow on wooden floor or on a side plank of shelves. In order to prevent the appearance of such sources of disease, steaming is carried out in the end of each cultivation cycle. During this process, the compost is warmed to the temperature of 70C and maintained at this temperature for not less than 12 hours. As a result, all pathogenic organisms die. After steaming the room is cooled and unloading is carried out in a short period of time. Spent compost is removed from the farm as fast as possible. If steamed compost remains in the growing room for a long time, the occurred biological vacuum gives a possibility for the infection to develop by spores of a mold and their recolonization of the substrate.

    Where the floors or walls are wooden, steaming isnt very effective; hence wood is a poor conductor of heat. After steaming it is necessary to use a disinfectant for wood.

    * (The optimal duration of the process (12 hours) was established through tests: Compost and casing layer, where mushrooms affected with the dieback virus grew, were steamed for different amount of hours at a temperature of 70C. After treatment, this material was added to healthy mushrooms and the appearance of disease was watched. It turned out that a small duration of steaming isnt enough to destroy the virus in compost and casing soil)

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