In recent years, silkworm fungal diseases have become more severe during the middle and late autumn seasons. This is largely due to favorable climatic conditions for fungal growth. When it rains, temperatures often hover around 25°C with high humidity of about 90%, creating an ideal environment for spore germination. In some breeding rooms, small-scale silkworm rearing tends to focus only on maintaining warmth and moisture, while neglecting proper ventilation and regular body cleaning of the silkworms. This oversight can lead to outbreaks of "zombie" disease in the early stages, causing damage that affects more than half of the silkworms.
Additionally, if mulberry gardens are not properly managed during the autumn season, pests such as mulberry insects, wild silkworms, and scale insects can carry fungal spores onto the leaves. These spores may then be introduced into the rearing area by the pests themselves, leading to cross-infection among the silkworms. Fungal diseases like white moss, yellow zombie, and green mold commonly occur during the middle and late autumn, with white fungus being the most prevalent.
To effectively control these diseases, strict disinfection measures must be taken before rearing young silkworms. The silkworms should be thoroughly cleaned and sterilized using a 1% available chlorine bleach solution. They can also be treated with a 1500-fold dilution of anti-Zongling No. 2 or a 100-fold chlorine-free solution. Old bedding, silkworm sand, and any accumulated dirt around the rearing area must be completely removed. The ground should be cleaned with clean water to prevent fungal spores from lingering inside and outside the silkworm room.
Timely application of antifungal agents is crucial in preventing spores from entering the silkworms' bodies. If there's a significant outbreak of stiff bone disease, bleaching powder, anti-pointing powder, or a "de-weathering agent" can be used to disinfect the silkworms twice daily. For smaller outbreaks, one treatment per day is sufficient until no signs of infection are observed. Another effective method is fumigation. Once the silkworms have finished eating their mulberry leaves, the room should be sealed, and fumigants such as formalin or chlorine-based smoke agents can be used. Apply approximately 1–2 grams of chlorine net per cubic meter, and 0.75–1 kilogram of formalin per square meter. Seal the room for about an hour to ensure maximum effectiveness against fungal spores.
Improving the rearing environment is essential. Silkworms should not be kept in damp conditions, and the sand should be removed promptly. Dry materials like fresh lime powder, ash, or dried straw can be sprinkled in the rearing area to help suppress spore germination. Trampoline rearing and film coverage can also aid in maintaining a stable environment. Half an hour before feeding, doors and windows should be opened for ventilation. During the middle and late autumn, temperature fluctuations between day and night are significant, and moisture condensation around the silkworms can worsen the situation. Therefore, careful attention should be given to controlling humidity and ensuring good air circulation to improve the overall rearing conditions.
Preventing insect pests is another critical aspect. Seven to ten days before rearing silkworms, the mulberry trees should be sprayed with an 8% emulsion of dichlorvos to eliminate Lepidoptera pests. During the rearing period, the leaves can be disinfected with a 1,000-fold dilution of a disinfectant solution or a 0.3% available chlorine bleach solution. Any diseased silkworms should be immediately removed, collected, and burned—never discarded to avoid spreading spores. Hands that have touched dead silkworms must be thoroughly washed and disinfected to prevent further contamination. Silkworms affected by stiff bone disease should not be stacked inside or outside the rearing room but should be moved away and properly fermented. Careful handling of the sand is necessary to avoid dust particles becoming airborne. Finally, the plastic film covering the floor should be removed to prevent fungal spores from spreading across the ground.
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