Fungi that are either contaminated or competition can cause bagged mushroom disease. Fibers of most contaminating fungi grow very fast, causing the growth of the mushroom fibers to halt. The borderline where mushroom fibers grow and fungus fibers grow is easily visible. Fungus contamination usually reduces mushroom production. If there is fungus around the opening of the packs, it will spread out all over the mushroom barn, causing damage and severely reduce production. There are many causes of fungi contamination. For example, leaving used packs in the barn area when it rains, as the wind blows the fungus, or the fungus falls into the water used for watering the mushrooms. Other causes can be that the concentrated fungal spores are not pure, the sterilization didn’t get rid of all the fungus, the packs are broken or damaged by insects, etc.