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水稻纹枯病早在1910年日本就发生了。在我国稻区也是常见病害之一。这个病害应属于热带系稻病,为什么近年在我国北方稻区发展成灾呢?其原因是;①纹枯病原田间积增;②品种比较感病;③水稻高产的要求,迫使其种植密度增高,施肥量增加,致使稻株易感病等。纹枯病一般在水稻分蘖盛期至末期以及抽穗期发病,特别是在抽穗期前后,遇到了高温多湿,病菌大量孳生,侵害叶鞘和叶片,引起病害大发生,使植株倒伏枯死。以辽宁气候来说,病害于6月中、下旬发生,7月中旬到8月中旬为发病高峰期。纹枯病的症状主要表现在叶鞘上,初在近水面处生有暗绿色水渍状、边缘不清楚的小斑,病斑继续扩大增多时,可互相融合成云纹状大斑。叶片也可出现云纹状病斑,严重时蔓延到穗颈部。病斑的蛛丝状物是病菌的菌丝体,以后结成黑褐色的菌核,很易掉落田里继续侵染,成为越冬菌源。
Rice sheath blight occurred as early as 1910 in Japan. Rice is one of the common diseases in our country. This disease should belong to the tropical rice disease, why in recent years in northern China rice area disaster? The reason is; ① Rhizoctonia field increased; ② susceptible varieties; ③ high yield requirements of rice, forcing its planting density Increased, fertilization increased, resulting in rice susceptible strains. Sheath blight generally occurs during the tillering to the late heading and heading stage, especially before and after the heading stage. It encounters high temperature and humidity and multiplies the germs. It infects the leaf sheaths and leaves, causing the diseases to occur greatly and lodging the plants. In Liaoning climate, the disease occurred in mid-June and late mid-July to mid-August for the peak incidence. Sheath blight symptoms are mainly manifested in the leaf sheath, the beginning of the surface near the birth of dark green water-like, unclear edge of the small spots, lesion continue to expand when the increase can be combined into a large cloud-like spots. Leaves may also appear moire-like lesions, severe spread to the panicle neck. Spider silk lesion is the mycelium of bacteria, after the formation of dark brown sclerotia, it is easy to fall into the field to continue infection, as a winter source of bacteria.