Symptoms are also called brown leaf blight and leaf scorch disease. It mainly occurs in the Yangtze River basin and the southern rice area. All parts of the ground can be infected. The main damage leaves, leaves infected with two symptoms. One is the appearance of moire-like lesions in high mountain areas. Firstly, water-soaked small spots are produced from the tip or the leaf margin of the lower leaves, and then quickly spread to the leaf base or inside. The center of the lesion is gray-brown, the outer edge is grayish green, and more obvious waves appear on the lesions at the later stage. Moire lines. Humid and rainy weather, the leaves rotted and rotted. Under high-humidity conditions, close to the diseased part produces a white powdery substance, ie, the conidia of the pathogen, and the dark tip of the tip of the tip is scattered with dark brown dots, ie, the ascospora shell of the pathogen. The other type was brown spotted blight in areas hit by strong winds. Small dark brown spots appeared on the leaves before they expanded into oblong-shaped lesions. Observing the light, there was a wide yellow halo around the lesions. The boundary is unclear, there is no ridges, the center of the lesion is pale brown to pale, the surrounding is brown, and the periphery has yellow halos. When the lesions are serious, the lesions make the leaves brown to death. Leaf sheath victims are heavier in the leaf occipital region of flag leaves. Dark brown spots appear at the beginning, and then expand into prismatic or irregular shapes. The lesions are light brown in the middle, surrounded by dark brown or purple brown, and the surrounding yellow part is wide. In severe cases, the entire leaf sheath withered, leaving the leaves brown, cobs and branches. The victim suffers from dark brown or purple-brown long-spotted lesions and pale brown to brown after death. The grains were damaged and there were brown spots with indistinct edges and a few brown spots.
The pathogen Gerlachia oryzae (Hashioka et Yokogi) W. Gams called Indigenous oryzae, a fungus belonging to the genus Deuteromycotina. Synonyms: Rhynchosporium oryzae Hasioka et Yokogi; Fusoma triseptatum Sacc; Fusarium nivale (Ces. ex Sacc.). Conidiophores are very short, colorless, conidial, short crescent or spindle-shaped, size 8.4-16.82.6-4.9 (μm), colorless or twin to quadruple. The sexual state is Monographella albescens (Thmen) Parkinson, Sivanesan et Booth = Phragmosperma sp.; Micronectriella (Calonectria) nivalis (Schaffn.) C. Bvoth; Metasphaeria albescens Thmen, both belonging to the fungus Ascomycota. Ascosi shells yellow-brown to dark brown, spherical or oblate spheroid, size 17271μm; ascaria cylindrical, size 44.7-70.38.5-13.2 (μm), endogenous ascospores 8, arranged in parallel staggered, ascospores oval, 3 Separator, size 14.9-26.43.6-6.4 (μm), colorless.
Transmission routes and pathogenic conditions The pathogens overwinter on diseased or diseased seeds. After the diseased seeds are sown, they cause decay. The diseased spores on the leaves were re-infested by wind and rain. The flooding stage is susceptible to disease onset and the disease is severe. After the leaves, a large number of dead leaves invade the branches, cobs, and grains. The growth temperature of pathogenic bacteria is 5-30°C, and the optimum temperature is 20-25°C. Sporulation temperature limit 15-30 °C, 25 °C optimum. The temperature is 19-25°C and the relative humidity is more than 98%. The rain is continuous and the disease is easy to spread. Generally, the incidence of indica and hybrid rice is heavy, and the indica rice has the lowest incidence. Low-lying terrain, poor drainage, excessive nitrogen application, and high density, rice plants are susceptible to the disease.
Control methods (1) Use disease-free seeds, avoid seeding in diseased fields, select seeds, and treat seed if necessary. See rice blast disease for treatment. (2) Strengthen agricultural control, adopt formula fertilization techniques, apply reasonable fertilizers, prevent partial application of nitrogen fertilizer, increase application of phosphorus and potash fertilizers, and shallow water irrigation, timely put down the field, see dry see wet, moist irrigation, reduce the humidity in the field. Cultivation density should not be too large. (3) Chemical control. Apply 20% triadimefon EC to 667m27-9g or 40% Bacillus to 30-40g at the time of rice breakage to full heading stage, and spray 40% Kelu San EC at 50-75ml or 50% methyl per 667m2 at the beginning of disease. Thiophene WP 75 g, 50% carbendazim WP 100 g, 20% tricyclazole wettable powder 74-100 g, colloidal sulfur 333 g, spray 50-75L of water. Onset of lime water 10-15kg per 667m2 or plant ash 20kg has a certain effect. In addition, 40% Rhizoctonia WP can be used, and 60-70g of medicine can be used per 667m2 of water, 60L of water can be sprayed, and it can also be used to treat rice tip blight, sheath rot, purple stalk disease, and rice smut disease.
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