Rice seedlings are particularly vulnerable to a fungal disease known as blight, caused by *Rhizoctonia solani*, a member of the Basidiomycota subphylum. This pathogen thrives in moist soil conditions and infects through wounds or lenticels on the roots and stems. The disease is most prevalent under warm (around 20°C) and humid conditions, or during periods of waterlogging, especially in July to September when high temperatures and drought alternate with excessive watering. These conditions promote infection, leading to damage in the roots and the base of the stem, as well as the above-ground parts of the plant.
In the early stages, symptoms appear as small, water-soaked spots on the roots and lower stems, which turn light brown and take on a semi-circular or irregular shape. Over time, these spots enlarge and cause the cortex of the roots and stems to rot. Within about a week, the affected seedlings begin to wilt, and the outer layers of the root and stem may fall away, leaving only the xylem tissue. The leaves exhibit similar symptoms to the young stems, showing signs of dehydration and yellowing.
To prevent and manage this disease, several measures can be taken. First, select a planting site with good drainage, elevated ground, and loose soil for the seedbed. Soil disinfection, application of organic fertilizers, or treatment with *5406* (a biological control agent) can help reduce the risk of infection. When the disease first appears, remove and burn infected seedlings promptly, and apply a mixture of wood ash and lime (in an 8:2 ratio) around healthy plants to prevent further spread. During the mid-stage of infection, spraying with 75% mancozeb at 800 times dilution or 75% chlorothalonil wettable powder at 600 times dilution is recommended.
Chemical control methods include the use of fungicides. For example, pentachloronitrobenzene can be applied at a concentration of 200–400 times, while 50% carbendazim diluted 800–1000 times can be sprayed once a week for 2–3 weeks. Alternatively, a Bordeaux mixture (1:1:200) or a 0.3–0.5% solution of lime sulfur can also be effective. Regular monitoring and timely intervention are crucial to managing this disease and protecting the health of rice seedlings.
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