How to prevent and control rice bacterial leaf streak?

Rice bacterial leaf streak, or fine streak disease for short, is a bacterial disease caused by the genus Xanthomonas and is one of the domestic plant quarantine pests. High temperature and high humidity favor the onset of the disease; when this coincides with heavy rain, hail or flooding, causing numerous wounds on the leaves, the disease spreads extremely easily. Long-term deep water irrigation as well as excessive and late application of nitrogen fertilizer also make the disease more severe. In mild cases, yield is reduced by about 10%, and in seriously affected fields the yield loss can reach 40%-60%.

Damage characteristics: Rice bacterial leaf streak mainly infects the leaves; the lesions initially appear as dark green, water-soaked, semi-transparent small spots, which then gradually spread along the direction of the leaf veins.

During expansion, they are restricted by the leaf veins, so the lesions appear as fine lines or short dashed lines, yellow-brown in color. When field humidity is high, honey-yellow bacterial ooze exudes from the surface of the diseased parts, in the form of dew droplets, densely clustered; it is more numerous and smaller than that of bacterial leaf blight, and after drying it forms small yellow gum-like granules shaped like dashed lines that do not easily fall off. In severe cases, the streaks merge into irregular yellow-brown to dead-white large patches, somewhat similar in appearance to bacterial leaf blight, but when held against the light many transparent fine streaks can be seen. When the disease is severe, the leaves curl, and the field takes on a yellow-white appearance.

Prevention and control methods: This disease spreads quickly; once it breaks out, chemical control alone is difficult to manage, so integrated control should be adopted.

① Quarantine: Strictly control the outward shipment of seeds from diseased areas to prevent the expansion of affected regions. ② Agricultural control: Select good disease-resistant varieties; different varieties differ in susceptibility and degree of loss. Practice shallow-water frequent irrigation and timely field drying. Avoid excessive and late application of nitrogen fertilizer. Appropriately increase the application of phosphorus and potassium fertilizers to improve plant resistance and prevent rice seedlings from growing excessively lush and lodging, which would induce the disease. ③ Chemical control: After finding the central diseased plants, begin spraying 20% Yekuning (Yeqingshuang) wettable powder at 100 grams per mu, mixed with 50 liters of water. When the control effect of Yekuning is not obvious, streptomycin sulfate or agricultural streptomycin at 4000 times dilution or strong chlorine essence at 2500 times dilution can be mixed in while applying Yekuning, which can significantly improve the control effect. In areas where the disease is widespread, before sowing the seeds should be soaked in clean water for 12-24 hours, then soaked in 300 times 85% strong chlorine essence for 12-24 hours, then removed, washed clean and sprouted before sowing. Spray strong chlorine essence once each at the three-leaf stage of the seedlings and before pulling up the seedlings. At the heading stage, use 4% copper amine, 20% Yeqingshuang and potassium permanganate plus table salt mixed with water for spray control, with an effect of over 80%.