In the summer and autumn of 2006, many regions across the country experienced prolonged high temperatures and low rainfall, which significantly impacted daily life and agricultural activities, especially the production of edible fungi. High temperatures disrupted the cultivation process, creating favorable conditions for certain bacteria to thrive. Many farmers suffered severe losses due to a lack of proper prevention and control measures. A friend of a farmer requested us to focus on the causes and preventive strategies for *Fusarium* species, aiming to raise awareness among mushroom growers and encourage early intervention.
Fusarium is a serious fungal pathogen that affects not only mushrooms but also various edible fungi such as straw mushrooms, oyster mushrooms, shiitake, white fungus, and reishi. According to microbiologists, it ranks as the second most common contaminant in mushroom cultivation, following *Trichoderma*. It is known for being stubborn and difficult to eliminate. If left unchecked, it can persist year after year, leading to significant yield reductions—up to 40% in some cases—and even total crop failure in severe situations.
The symptoms of Fusarium infection typically appear on the fruiting bodies rather than the mycelium. Infections usually take at least 11 days to manifest. The presence of mycelium can speed up spore germination. The disease often starts from contaminated soil or old mushroom beds. Water, tools, and human activity can spread the pathogen. If infected during the bud formation stage, the mushrooms may develop abnormally, appearing as irregular, mabul-like tissue before they are fully formed. These mushrooms tend to grow faster than normal ones. If infected during the early growth phase, the caps may deform, stems twist, and the inside of the mushroom becomes hollow. White mycelium appears at the base of the cap and stem, eventually turning dark brown with water droplets and an unpleasant odor.
Fusarium thrives in topsoil between 2-9 cm deep, with optimal growth at 25°C. It grows very slowly at 10°C and stops growing above 35°C. Laboratory tests showed that the spores die after 4 hours at 56°C or 1 hour at 65°C. The pathogen spreads through soil, water, humans, tools, and insects. Poor ventilation, high humidity, and high temperatures further promote its development.
To control Fusarium, it's essential to disinfect the mushroom house and structures before planting using a 5% bleach or formaldehyde solution. For cover soil, use deep soil below 30 cm and avoid surface soil or areas where previous mushroom waste was discarded. After preparation, the soil should be dried in the sun and treated with a disinfectant. In heavily affected areas, a small amount of medication may be applied. After the second batch of mushrooms, a 700-fold diluted solution can be sprayed on the beds.
Once the disease is detected, stop watering immediately and increase ventilation. Infected mushrooms should be removed and burned, not discarded. If a large number of mushrooms are present, harvest the healthy ones first, then spray the affected area with a 500-fold solution every 3-7 days for 3-4 applications. This method has proven highly effective.
Other important precautions include disinfecting used tools with 2% formaldehyde and washing hands thoroughly to avoid spreading the pathogen. In severely affected areas, avoid changing the planting schedule arbitrarily. Farmers in infected areas should not visit each other to prevent the spread of spores to other farms. By taking these steps, mushroom growers can significantly reduce the risk of Fusarium and protect their crops effectively.
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