Jasmine white feather disease is one of the most devastating diseases affecting jasmine plants. When the infection becomes severe, 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 disease primarily affects the root neck and roots, and under favorable conditions, it can spread to the lower leaves. The affected areas turn brown and begin to rot, gradually forming a white, silky film that spreads radially with a sharp boundary. The mycelium can extend into the surrounding soil, covering the entire pot with white hyphae. As the sclerotia form on the mycelial membrane, they start off white and gradually turn yellow, then dark brown, resembling small rapeseed grains in size. Once the cortex dies, the leaves become wilted and eventually the entire plant dies. In high humidity conditions, the hyphae can directly spread to the lower leaves, causing large white silk-like membranes that cover the lower branches and leaves, leading to water-soaked spots and the formation of hyphae on the silk layer.
The pathogen responsible for this disease is *Sclerotium rolfsii*, a fungus belonging to the subphylum of Basidiomycota, class of filamentous spores, without a sporophore, and classified under the genus *Sclerotium*. The sclerotia are initially white, later turning from light brown to dark brown, with a smooth, spherical or nearly spherical surface. Their diameter ranges from 0.8 to 2.3 mm, closely resembling rapeseed. The optimal temperature for the growth of the pathogen is between 32°C and 33°C, with a maximum of 40°C and a minimum of 8°C. It can survive in a wide pH range, from 5 to 9. The pathogen infects over 200 plant species and overwinters in the soil, infected plant residues, and weeds. Sclerotia can remain viable in the soil for more than four years, but their survival is short in high humidity environments and they are not resistant to flooding. The pathogen spreads through mycelium in the soil and can be transmitted by human activities such as moving infected seedlings, contaminated soil, or sick pots. Using unsterilized soil or garden soil for planting can easily lead to infection, especially when there's continuous planting in the same area or reuse of infected pots. High humidity is a major factor that promotes disease development.
To manage this disease, several control methods are recommended:
1. **Cultural Control**: Implement crop rotation and centrally treat infected pots and soil. It is advisable to dispose of them in paddy fields. Use soil from disease-free plots, preferably from rice fields. Ensure organic manure is fully decomposed before application. Cut propagation materials only from healthy plants. Avoid piling up plants in greenhouses during winter.
2. **Remove Infected Plants and Disinfect Soil**: Early detection is crucial. Infected plants should be promptly removed and destroyed by burning or deep burial. The affected soil should be treated with 86.2% copper master diluted 800–1200 times, 50% Johnson’s ammonium at 500 times, or lime powder. Removal should occur before sclerotia develop.
3. **Chemical Control**: Apply 50% tetrazine at 1000g per 666.6 square meters. During the early stages of the disease, spray 50% dexamethasone diluted 1000 times every 7–10 days to kill the pathogen in the soil. Use 70% thiophanate-methyl or 50% carbendazim at 1000 times dilution to sprinkle around the base of the plant to prevent spread. Other fungicides can be used afterward. Trichoderma-based products like Pentu 82 (a product from Zhejiang Agricultural University) can also be used. Mix 0.5% of the Trichoderma preparation with the soil before planting. Infected pots and soil can also be replaced with fresh, clean soil.
4. **Physical Control**: Sterilize soil using heat treatment to eliminate pathogens.
5. **Biological Control**: Using *Trichoderma harzianum* has proven effective in controlling jasmine white feather disease. Cultivate the Trichoderma strains first, then mix them with sterilized bran to prepare a biological agent. When applying, mix the preparation evenly with fine soil and apply it to the growing medium. Maintain proper soil moisture to promote the growth of *Trichoderma*, which helps suppress the pathogen and prevent disease.
6. **Fertilization Management**: Applying undecomposed organic fertilizers on the soil surface can increase the risk of disease. Therefore, organic fertilizers such as manure should be used as basal fertilizers and deeply incorporated into the soil. If used as topdressing, they must be fully decomposed before application.
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