How to Control Rice Grain smut

Symptoms are also known as smut, rice ink smut, Wumigu and so on. Distributed in the Yangtze River Basin and the south of China, it mainly occurs from flowering to milk ripening stage of rice, only injuring grains, one or several grains per panicle or even dozens of grains per panicle, usually showing disease when rice is near maturity. The infected rice grain is dark green or yellow, with black powder in it, the abdomen is split at maturity, showing black powder, there is a black tongue protruding between the inner and outer glumes of the diseased grain, and there is often black liquid exudation, polluting the appearance of the grain. When the diseased seeds are removed, it can be seen that some or all of the seeds turn into black powder, that is, the thick chlamydospores of the pathogen.

Pathogen Tilletiabarclayana (Bref.) Sacc.etSyd. It is called Pennisetum smut, which belongs to basidiomycete subphylum fungi. Neovossiahorrida (Tak.) Padw.etAzmatKahn. The spores are stacked in the host ovary, wrapped in glumes, and some spikelets are destroyed to produce black powder. Chlamydospores spherical to broadly ovate or oval, black, size 25-32 × 23-30 (μ m), surface densely dentate, colorless to nearly colorless, tip, base polygonal slightly curved, 2.5-4 (μ m) high; basidiospores linear, colorless, septum, size 38-55 × 1.8 (μ m); secondary microspore membrane intestinal, size 10-14 × 2 (μ m).

The pathogen of transmission and disease condition overwintered in seeds and soil as Alternaria alternata. Seed-borne bacteria into paddy field and soil with sowing is the main source of bacteria. The chlamydospores can survive for 1 year under natural conditions, survive on stored seeds for 3 years, survive in 55 ℃ constant temperature water for 10 minutes, and still germinate through digestive tract bacteria such as poultry and livestock. The bacteria need to go dormant for more than 5 months, air temperature higher than 20 ℃, high humidity, ventilation and light, chlamydospores germinate and produce basidiospores and secondary microspores. Large ears of rice spread to heading and flowering by airflow, invade floral organs or young seeds, and propagate in grains to produce chlamydospores. If the parents of rice from booting to heading and flowering stage and hybrid rice seed production field meet poorly at this flowering stage, the disease phase rate is high and the disease is serious. In addition, more Rain Water or high humidity, the application of too much nitrogen fertilizer will also aggravate the occurrence of the disease. In different combinations of hybrid seed production, there is a phenomenon that the inner and outer glumes of the female parent can not be closed, which is called glume opening. A combination with a high rate of innovation, such as Xianyou 63, with an opening rate of 30%, 40%, will have a high incidence. There is a great difference in the incidence among varieties. Shanyou 63 was planted in the first year, the diseased ear rate was as high as 92%, and the diseased grain rate was 25.19%.

Prevention and control methods (1) carry out quarantine and strictly prevent the introduction of infected rice seeds into disease-free areas. (2) pay attention to clarify the primary and secondary effects of soil bacteria and seed bacteria in the local old seed field. In areas where seeds are mainly infected, seeds must be selected with 10% salt water before sowing, disinfect the diseased seeds, and then disinfect the seeds. See rice blast. (3) crop rotation should be carried out for more than 2 years, and the manure of poultry and livestock in the disease area should be retted and matured and then applied to prevent the spread of soil and manure. (4) strengthen cultivation management, avoid partial and over-application of nitrogen fertilizer, and make seed fields meet at flowering stage by planting seedling number, seedling age and adjusting seedling evenness. Spraying gibberellin at the late booting stage can reduce the incidence of the disease. (5) in the area or year of hybrid seed production or planting of susceptible varieties, 14% black rickets was sprayed once at the end of flowering peak and at the beginning of heading of rice.

2400 times solution of glue suspension or 250x solution of Mihei No. 1 glue suspension. In the year of mild illness, you can spray it once at the end of the peak of flowering. In addition, 30% encyclopedia EC per 667m275ml or 50% WP 50% paracetamol suspension 200ml, 25% triadimefon WP 50 g, 50 L water spray can also be selected. When using triketone, you should avoid flowering and apply it in the afternoon to avoid drug damage. In addition, it can also be sprayed 2000 times in rice panicle stage to effectively control the disease, as well as sheath blight, rice false smut and leaf sheath rot. (6) selecting disease-resistant varieties. In the preparation of hybrid rice, the varieties with closed glumes should be selected to reduce the disease.