Four key passes must be secured in controlling rice sheath blight

In recent years, sheath blight has risen to become the most important disease of rice, and it has four major characteristics: First, it occurs over a wide area. Second, there are very few varieties resistant to sheath blight. Third, the degree of damage is increasingly serious, even causing the plants to break through the top and lodge. Fourth, it first develops on the lower part of the rice plants, making it easy to overlook and miss the favorable timing for control. In control strategy, strictly securing the four passes is the key.

1. The pass of salvaging sclerotia. Sheath blight mainly overwinters in rice fields in the form of sclerotia, and overwintering sclerotia generally have 60%-70% able to germinate from winter and spring through to early rice transplanting. The vast majority of sclerotia are lighter than water and can float with the water for a long time. After the rice field is irrigated, salvaging the sclerotia floating on the water surface can reduce the source of primary infection and effectively lessen the incidence of sheath blight in the early stage of rice. The salvaging method is: after the field surface is leveled, appropriately deepen the water layer, then use tools such as a winnowing basket to scoop up the floating debris and sclerotia on the water surface along the downwind field edges and field corners, carry them away from the rice field, and bury them deep or dry them and burn them.

2. The pass of fertilizer and water management. Strengthen fertilizer and water management to improve the disease resistance of the seedlings. In fertilization strategy, the following three principles must be grasped: First, value base fertilizer, apply more farmyard manure and organic fertilizer, and the amount of base fertilizer should generally account for 60% of the total fertilization amount. Second, rationally match the three elements of nitrogen, phosphorus and potassium, and especially do not apply nitrogen fertilizer in excess. Third, topdressing should be early and appropriate, and should be applied according to the principle of "heavy at the front, controlled in the middle, supplemented at the back." In water management, implement the irrigation method of shallow, exposed, dried, and living, that is, during the rice tillering stage implement frequent shallow irrigation and appropriately expose the field; at the end of tillering, dry the field moderately to control ineffective tillering and inhibit excessive growth of stems and leaves; after entering the booting stage, implement living-water irrigation; at the grain-filling and ripening stage, persist in alternating dry and wet to promote clean and healthy growth of the seedlings, free of disease until old.

3. The pass of toxic-soil prevention. Using daojiaoqing toxic soil for prevention can inhibit the growth and germination of sheath blight mycelium. Apply it within 15-20 days after rice transplanting, using 250 grams of 20% daojiaoqing per mu mixed with 25 kg of fine soil, evenly broadcast into the rice field, and the preventive effect is remarkable. But when using daojiaoqing, it must be before the booting stage, and use is prohibited at the booting stage or in the late growth period.

4. The pass of chemical control. The occurrence of rice sheath blight generally develops slowly in the early stage and rises relatively quickly in the later stage. Therefore, in the peak tillering stage of early rice, field investigation should be strengthened. When encountering high-temperature and high-humidity weather, when the rate of diseased hills in the field is about 30%, chemical control should be applied immediately to control the spread of the disease damage. For the chemical, one packet of jinggangmycin powder per mu or 0.2 kg of jinggangmycin liquid formulation mixed with 50 kg of water can be selected, and according to the degree of incidence and weather conditions, spray 2-3 times consecutively. Spraying should focus on the middle and lower parts of the rice plants to achieve good results.