In the summer and autumn of 2006, many regions across the country experienced prolonged periods of high temperatures and low rainfall, significantly impacting daily life and agricultural activities—particularly the cultivation of edible fungi. High temperatures disrupted the growth of mushrooms, while certain heat-loving bacteria thrived, causing serious damage to mushroom farms. Many farmers suffered heavy losses due to a lack of preventive measures. A friend of a farmer asked us to focus on the causes and control methods of *Fusarium* species, aiming to raise awareness among mushroom growers and encourage early prevention. (Yuan Shiping, Suizhou City, Hubei Province, Edible Fungus Disinfectant Factory http://syxdjc.aweb.cn)
1. **Harmful Effects**: *Fusarium* mildew, also known as wet bubble disease or white rot, is a fungal pathogen that not only affects mushrooms but also most edible fungi, including straw mushrooms, oyster mushrooms, shiitake, white fungus, and reishi. Experts in the field consider it the second most common contaminant after *Trichoderma*. It is highly persistent and difficult to eliminate. If left unchecked, it can recur year after year, reducing yields by over 40% in some cases, and in severe situations, even leading to total crop failure.
2. **Symptoms**: After extensive research, it was found that the pathogen infects only the fruiting bodies, not the mycelium. Infection typically takes at least 11 days before symptoms appear. The growth of mycelium can accelerate the germination of *Fusarium* spores. The first signs of infection in oyster mushrooms often originate from the cover soil or old mushroom beds. The disease spreads through water, tools, and human activity. If infected during the bud formation stage, the mushrooms may develop irregular, mabul-like structures instead of normal buds. These mushrooms appear 3-4 days earlier than usual. During the young bud stage, the mushrooms may continue to grow, but their caps may develop abnormally or stop growing altogether. The stems may become swollen and twisted, and the inside of the mushroom becomes hollow. White mycelium appears at the base of the cap and stem, later turning dark brown with oozing brown liquid and an unpleasant odor.
3. **Disease Occurrence**: The pathogen is commonly found in the topsoil between 2–9 cm. It thrives best at 25°C, grows slowly at 10°C, and stops growing above 35°C. Studies show that the pathogenic spores die at 56°C after 4 hours and at 65°C after 1 hour. The pathogen spreads through soil, water spray, humans, tools, and insects. Poor ventilation, high temperature, and high humidity further promote its spread.
4. **Control Methods**: Before planting, the mushroom house and shelves should be disinfected using a 5% bleach solution or 5% formaldehyde solution. For the cover soil, deep soil below 30 cm should be used, avoiding surface soil and soil from areas where mushroom waste has been discarded. After preparation, the soil should be dried in the sun and treated with a disinfectant. In severely affected areas, an appropriate amount of medication can be applied. After the second batch of mushrooms, a 700-fold dilution of the solution can be sprayed on the mushroom bed. (Suizhou City, Hubei Province, Edible Fungus Disinfectant Factory http://syxdjc.aweb.cn)
After detecting the disease, immediately stop watering and increase ventilation in the mushroom house. Infected mushrooms should be removed and burned, not thrown away, especially in severe cases. When many mushrooms are present, harvest the healthy ones first, then spray the affected area with a 500-fold solution, repeating every 3–7 days for 3–4 times. This method has proven very effective.
5. **Other Precautions**: 1. All mushroom tools should be disinfected with 2% formaldehyde. Hands must be cleaned promptly, and avoid touching the mushroom bed directly. 2. Do not change the planting date arbitrarily in seriously infected areas. 3. Farmers in infected areas should avoid visiting each other to prevent spreading the pathogen to other mushroom houses.
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