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症状水稻稻瘟病主要危害叶片、茎秆、穗部。因危害时期、部位不同而分为苗瘟、叶瘟、节瘟、穗颈瘟、谷粒瘟。(1)苗瘟。发生于三叶期前后,由种子带菌所致。一般不形成明显病斑,病苗常变黄褐色枯死;潮湿下,病部可长出灰绿色霉层。(2)叶瘟。在整个生长期都可能发生。分蘖至拔节期危害较重,分为四种类型。急性型:病斑较小、不规则、暗绿色、水渍状,斑上密生灰绿色霉层。慢性型:病斑梭形,外围有黄
Symptoms Rice blast is the main hazard to leaves, stems, ears. Due to the harmful period, different parts and divided into seedling blast, leaf blast, section blast, panicle blast, grain blast. (1) Seedling blast. Occurs before and after the three-leaf stage, caused by the seed carrier. Generally do not form a distinct lesion, the disease often change brown withered dead; wet, the disease may grow gray mold layer. (2) leaf blast. It can happen throughout the growing season. Tillers to join the more serious hazards, divided into four types. Acute type: lesion smaller, irregular, dark green, water-like, spot on the gray-green moldy layer. Chronic type: fusiform spindle, peripheral yellow