Jasmine white feather disease is one of the most devastating diseases affecting jasmine plants. In severe cases, it can lead to plant death and significantly reduce yield. This disease is commonly found in regions such as Suzhou, Hangzhou, Shanghai, Nanjing, Fuzhou, and Taiwan. The infection primarily affects the root neck and roots, and under favorable conditions, it spreads to the lower leaves. The affected areas turn brown and begin to rot, gradually forming a white, silky film that radiates outward with a sharp boundary. The mycelium can spread into the surrounding soil, creating a dense network of white hyphae throughout the potting medium. Over time, the sclerotia—small, hard structures—develop on the mycelial layer, starting off white and turning yellow, then dark brown, resembling small rapeseed grains. Once the cortex dies, the leaves also wither and die, eventually causing the entire plant to perish. In highly humid environments, the hyphae can directly spread to the lower leaves, forming large white silk-like membranes that cover the lower branches and leaves, leading to water-soaked spots and the growth of new hyphae on the membrane.
The pathogen responsible for this disease is *Sclerotium rolfsii*, a fungus belonging to the subphylum of Basidiomycota, class of Filamentous Spores, with no sporophore and a genus known for producing small sclerotia. These sclerotia are initially white, then transition to brownish or dark brown, with a smooth, spherical or nearly spherical surface, ranging in size from 0.8 to 2.3 mm. They closely resemble rapeseed in appearance. The optimal temperature for the pathogen's development is between 32–33°C, with a maximum tolerance up to 40°C and minimum at 8°C. It can survive in a wide pH range, from 5 to 9.
The disease is widespread, affecting over 200 plant species. *Sclerotium rolfsii* overwinters in the soil, infected plant debris, and weeds. Sclerotia can remain viable in the soil for more than four years, but their survival is limited in high humidity conditions and they are not resistant to flooding. The pathogen spreads through soil-borne mycelium and can be transmitted by human activities such as moving infected seedlings, contaminated soil, or diseased pots. Using unsterilized garden soil or waste soil for planting can easily lead to infection, especially when the same pots or soil are reused repeatedly. High humidity levels also increase the likelihood of disease occurrence.
Control measures include several approaches:
1. **Cultural Control**: Practice crop rotation and properly dispose of infected pots and soil by burying them deeply or using them in paddy fields. Use soil from disease-free plots, preferably from rice fields. Ensure organic manure is fully decomposed before application. Select propagation material from healthy plants, and avoid overcrowding plants during winter in greenhouses.
2. **Remove and Disinfect**: Promptly remove and destroy infected plants by burning or deep burial. Before sclerotia form, treat the affected area with copper-based fungicides (such as 86.2% Copper Master diluted 800–1200 times), 50% Benomyl diluted 500 times, or lime powder. Early removal is crucial to prevent further spread.
3. **Chemical Control**: Apply 50% Thiophanate-methyl at a rate of 1000g per 666.6 square meters. During the early stages of infection, use 50% Dexamethasone diluted 1000 times, applying it every 7–10 days. Alternatively, use 70% Thiophanate-methyl or 50% Carbendazim at 1000 times dilution to spray around the base of the plant. Other fungicides can be used afterward. Trichoderma-based preparations, such as those made by Zhejiang Agricultural University, can be mixed with soil at 0.5% concentration for effective control.
4. **Physical Control**: Sterilize soil or pots by heating to eliminate pathogens.
5. **Biological Control**: Use *Trichoderma harzianum*, a beneficial fungus that effectively suppresses *Sclerotium rolfsii*. Cultivate the strain, mix it with sterilized bran, and apply it to the soil. Maintain proper moisture to promote its growth and inhibit the pathogen.
6. **Fertilization Management**: Avoid applying undecomposed organic fertilizers on the soil surface, as this increases the risk of disease. Instead, use well-decomposed organic materials as basal fertilizer, thoroughly mixed into the soil. If used as topdressing, ensure the material is fully decomposed before application.
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