Symptoms are also known as rice leaf blight. Every rice area in the country occurs evenly. From the seedling stage to the harvest stage can be the disease, rice plants can be damaged above the ground, with more leaves. When the seed buds are infested, the colebra is browned, the buds are not drawn out, and the cotyledons are withered. The incidence of leaf and sheath in seedling stage is mostly elliptic lesions, such as the size of flax pellets, dark brown, sometimes the lesions expand into strips, and the lesions often die. The leaves of adult plants become brown dots at the beginning of disease and gradually expand into elliptic spots, such as the size of sesame seeds, the central spot of lesions is brown to gray, and the edges are brown. There are yellow halos with different shades around, and serious irregular spots are formed. The diseased leaves dry inward from the tips of the leaves, and they are brownish-brown. Black molds (spores and conidia of germs) are produced on the dead seedlings. Lesions on leaf sheaths were initially oval-shaped, dark brown in colour, brownish on the edges, water-stained, and later changed to an irregular large spot with a central taupe. The affected neck of the panicle neck and branch stems are dark brown and cause ear dryness. Grains infected in early grain-enhanced grains spread to full grain and cause grain gluten. The lesions in later stages are small and the edges are not obvious. The diseased grain is brittle and brittle. When the climate is humid, the above-mentioned disease minister has a black fungus layer, which is a conidiophore and conidia of the pathogen.
The pathogen, Bipolaris oryzae (Breda de Hann) Shoem, is a genus of Deinophyta spp. Different Helminthosporium oryzae Breda de Haan. Conidiophores 2-5 bundles protruding from stomata, not branched, slightly curved, with septa. Conidiophore terminal, decumbating or long cylindrical, slightly curved, brown, with 3-11 septa, size 24-12211-23(μm), cochleobuloide miyabeanus (Ito et kuribayashi) Drechsler ex Dastur said The bacterium Mycobacterium spp. is an ascomycete subphylum, which is found only in the culture medium and does not occur under natural conditions.
Transmission routes and pathogenic conditions The pathogenic bacteria have become the source of infestation early in the year with mycelium overwintering on the diseased body or attached to the seed. Conidia on lesions can survive for 2-3 years under dry conditions. Latent mycelium can survive for 3-4 years. Mycelium turns into soil and loses its vitality after one winter. After the diseased seeds are sown, the latent mycelium can directly invade the seedlings. The conidia can be blown by wind to the fields of Putian or Honda. The germinating hyphae can directly invade or invade from the stomata. When the conditions are suitable, the disease will appear quickly and form points. Conidia, re-infested by wind and rain. High temperature, high humidity, and heavy fog may cause disease. Acidic soils, sandy soils, phosphorus deficiency and potassium incidence. Dry field incidence
weight. The temperature limit of mycelial growth is 5-35°C, and the optimum temperature is 24-30°C. The conidia formation temperature limit is 8-33°C and 30°C is the most suitable. Germination temperature limit 2-40 °C, 24-30 °C optimum. The spore germination must have water droplets, and the relative humidity is greater than 925. It can invade the host within 4 hours at 25-28°C under saturated humidity.
Prevention and control methods (1) Depth-enhanced recommendation, and reduce the source of bacteria. Diseased straw should be disposed of in time. (2) Choose to keep seed or disinfect seeds in disease-free fields. (3) Increase the use of decomposed compost as a base fertilizer, timely top-dressing, and increase phosphorus and potassium fertilizers. In particular, the application of potash fertilizer can increase the plant disease resistance. Pay attention to drainage of acidic soil, proper application of lime. Ground irrigation should be conducted shallowly to avoid poor ventilation caused by long-term flooding. (4) Chemical control See rice blast disease.
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