Sorghum sheath blight

The symptom of the disease is common in the north and Taiwan, the hybrid sorghum is more serious, and it also occurs in central and southwest China. It is mainly harmful to leaf sheath and can also be harmful to leaves. After the disease, water-immersed lesions first appeared on the stem near the ground, and then purplish red and gray spots appeared on the later leaf sheath. In the late growth period or under rainy and humid weather, brown sclerotia appeared in the diseased part. The disease can also spread to the top of the plant, causing damage to leaves. The seriously diseased plants died early. The leaf sheath at the base of the stem was infected with a small white-green water-immersed spot, and then expanded into an oval, brown around and lighter spot in the middle. The infected leaves showed gray-green to gray-white cloud spots, and most of the disease spots fused into tiger spots, resulting in the death of the whole leaf. When the humidity is high, white hyphae protrude in the leaf sheath, and some produce small black-brown sclerotia. According to the two mycelial fusion groups of pathogen Rhizoctonia solani Kuhn AG-l-IA and AG-5, the mycelial fusion group of AG-1-IA isolated from North China accounted for 77% of the mycelial fusion group, 19.2% of the mycelium fusion group, and 3.8% of the mycelial fusion group of Magmuri 4. The phenotype is Thanatephoruscucumeris (Frank) Donk. It is called Coryneomycetes, belonging to basidiomycetes subphylum fungi. The temperature limit for mycelial growth is 7 ℃, 40 ℃, and the optimum temperature is 26 min, 32 min. The sclerotia could germinate and produce hyphae in 12 days when the sclerotia was 26 / 32 ℃ and the relative humidity was above 95%. The mycelium growth was suitable for pH5.4-7.3. Only when the relative humidity is higher than 85% can the hyphae invade the host. The route of transmission, disease conditions and control methods see maize sheath blight.