Rice smut
Symptoms are also known as smut, rice smut, and Umi Valley. Distributed in the Yangtze River basin and the south of China, it mainly occurs during the period from the flowering stage to the milk stage of rice, and it only harms the grain, and suffers from 1 or several grains or even tens of grains per panicle. The infected rice grain was dirty green or dirty yellow with black powder inside. When mature, the abdomen split and exposed black powder. There was a dark tongue between the inner and outer linings of the diseased granules. Black liquid often bleeded out. Pollution grain appearance. The seeds can be seen as part or all of the black powder in the seeds, ie the chlamydospores of the pathogen.
The pathogen Tilletia barclayana (Bref.) Sacc. et Syd. is known as Pennisetum japonicum, a basidiomycotina fungus. Synonyms: Neovossia horrida (Tak.) Padw. et Azmat Kahn. The spores were born in the host's ovary and were covered with glume. Some spikelets were destroyed and black powder was produced. The chlamydospores are globose to broadly ovate or elliptic, black, 25-3223-30(μm) in size, densely denticulate on surface, colorless to nearly colorless, apical, base slightly curved, 2.5-4. Μm); spore-lined, colorless, no septum, size 38-551.8 (μm); secondary microspore membrane gut, size 10-142 (μm).
Pathogens and Pathogens The pathogens thrived in the seeds and in the soil with Fusarium oxysporum. Seed borne with bacteria into the rice fields and soil bacteria is the main source of bacteria. The fungus chlamydospore is strong in resilience, can survive for 1 year under natural conditions, can survive for 3 years on stored seeds, and can still survive in a constant temperature water immersed at 55°C for 10 minutes. It can survive through poultry, livestock and other digestive tract bacteria. Can be germinated, the bacteria need to sleep more than 5 months, the temperature is higher than 20 °C, high humidity, ventilation, light phlegm spore germination, resulting in spores and secondary spores. The ear of rice that is spread to the heading and flowering by the air flow is large and invades the flower or young seed, and the chlamydospores are propagated in the grain. From the time of booting to heading and flowering stage in rice, and the poor parental flowering period in the hybrid rice production field, the incidence rate is high and the incidence is heavy. In addition, excessive rainfall or high humidity, excessive application of nitrogen fertilizer will also aggravate the disease. In the different combinations of hybrid seed production, there is a phenomenon that the female parent and the female end are unable to be closed, which is called the opening. The combination of high opening rate, such as Xianyou 63, opening rate of up to 30% -40%, the incidence rate is high. There was a large difference in morbidity between the varieties. The first year of the Shanyou 63 system was used for the cultivation, and the panicle rate was as high as 92%, and the disease rate was 25.19%.
Prevention methods (1) Quarantine shall be carried out to prevent the introduction of bacteria-infected rice into disease-free areas. (2) Attention should be paid to clarifying the roles and effects of both old-fashioned farmland soil carriers and seed carriers. In regions where seed-borne bacteria are predominant, 10% saline must be selected before sowing, and diseased grains should be eliminated. Then the seeds should be disinfected. For the disinfection method, see Rice Blast. (3) After more than two years of rotation, the poultry and livestock waste in the ward area will be decomposed before application to prevent the spread of soil and manure. (4) Strengthen the cultivation and management, avoid partial application and over-application of nitrogenous fertilizers, and adopt the system to plant seedlings by planting and transplanting the number of seedlings, seedling age, and adjusting the cocoon's uniformity so that the flowering period meets. Spraying gibberellic acid at the late booting stage can reduce the incidence. (5) Hybrid planting or planting of susceptible varieties, areas or years of severe disease, at the end of the peak period of rice flowering and the beginning of heading, 14% of each spray
Suspension gel 2400 times or black 1 suspension 250 times suspension. In mild disease years, it can be sprayed once at the end of full bloom. In addition, 50 % of water may be sprayed with 30% enzymatic emulsion per 667m275ml or 50% wettable powder 50, 40% exterminate disease suspension 200ml, 25% triadimefon wettable powder 50g. When using triketone, avoid flowering and apply pesticide in the afternoon to avoid phytotoxicity. In addition, it can also effectively control the disease by spraying 25% enemy demulsifiable oil 2000 times liquid in the ear of rice, and it can also treat sheath blight, rice smut, and leaf sheath spoilage disease. (6) Selection of disease-resistant varieties. In the preparation of hybrid rice, it is necessary to use closed varieties to reduce the incidence.
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