After late rice heading, be cautious of rice grain diseases, and master the control methods

Rice grain blight, also known as glume blight, is a fungal disease and one of the common diseases in the late stage of late rice. This disease occurs only on the grains. In the early stage of the disease, small brown spots appear on the grains, which then gradually expand to cover most or all of the grain. Lightly affected grains can still fill, but the rice quality is loose and easily broken; severely affected grains become empty and shriveled, causing yield decline. At heading and flowering, if storms occur, the grains rub against each other and create wounds, which facilitate pathogen invasion, resulting in more severe disease. Generally, disease is more severe in rice fields with excessive nitrogen fertilizer and insufficient phosphorus and potassium fertilizer; disease is also more common in cold-soaked fields or fields irrigated with cold-soaked water. For control of this disease, generally after heading, for severely susceptible rice fields, 0.5 kg of copper sulfate, 0.5 kg of quicklime, and 100 kg of water per mu can be used to prepare Bordeaux mixture for spray control, spraying 75 kg of solution per mu. Alternatively, after full heading of rice, 30 ml of Tonggaoshang (27.12% copper hydroxide sulfate suspension concentrate) mixed with 30 kg of water can be sprayed, which has a good preventive effect.
Rice kernel smut. Rice kernel smut is one of the main diseases of hybrid late rice, with only some grains on each panicle affected. This disease is a fungal disease. Chlamydospores attach to seeds to overwinter, and under suitable conditions the spores germinate. Although it can infect throughout the entire heading stage of rice, the chance of invasion is greatest during the full flowering stage. If autumn wind and autumn rain occur at this time, the disease will be even more severe. Late rice fields with excessive or late nitrogen fertilizer application are prone to this disease. After the disease occurs, field chemical control can use 20% triadimefon emulsifiable concentrate at 1000-1500 times dilution, spraying 50 kg of solution per mu, with a control effect of over 80%, or 40% miebingwei suspension concentrate 200 g mixed with 50 kg of water for spraying. Secondly, 50% carbendazim wettable powder at 500 times dilution, or 40% thiophanate-methyl sulfur suspension concentrate at 400 times dilution also have good control effects.
Rice false smut. This disease infects hybrid late rice before and after heading, and appears on the grains of rice panicles at the milk-ripening stage. A panicle may bear as few as 1-2 diseased grains, or as many as more than 10. Affected grains cannot fill. At first the false smut ball is very small, then it pushes open the glumes and exposes a light green mass, which is the spore cushion of the pathogen. The pathogen overwinters in seeds or soil, and infects and causes damage again the following year. The optimum growth temperature for the pathogen is 26°C-28°C. Therefore, with little rain, plenty of sunshine, and hot weather, the disease occurs more frequently. Rice fields with excessive or late nitrogen fertilizer application, and fields where the rice leaves are dark green at heading, are prone to the disease. The degree of disease varies among different varieties. To control rice false smut, be sure to seize the time to spray for prevention 5-7 days before heading. If continuous rainy weather causes the 5-7 days before breakage of the boot to be missed as the suitable application period, as long as the pesticide is applied before full heading of late rice, there will still be a good control effect. The pesticides selected include: Tonggaoshang, using 30 ml per mu each time mixed with 30 kg of water for spraying, which can kill the pathogen in the fungal mass on diseased grains, causing it to shrink and fall off when the weather is clear and dry, greatly reducing the number of diseased grain balls in the field. In addition, 30% Shoumiao emulsifiable concentrate, 30% Jiarun emulsifiable concentrate, and 30% Shimiao emulsifiable concentrate can also be selected, all with good control effects. (Source: Farmers' Daily 2009-8-31)