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1.主要病害发生特点 (1)大葱紫斑病大葱紫斑病,也叫黑斑病,是大葱常发病,此病主要为害叶和花梗,也可为害鳞茎。病斑多从叶尖或花梗中部开始发生,几天后即可蔓延至下部。发病初期病斑小,灰色至淡褐色,中央微紫色。之后很快扩大为椭圆或纺锤形,凹陷,暗紫色,上生黑色煤污点状物,常形成同心轮纹。病斑常扩大到全叶,或绕花梗一周,使叶和花梗倒折。环境条件适宜时,引起外叶大量枯死,严重影响大葱的产量和品质。采种株的花茎被害后,易影响种子成熟。病菌以菌丝潜伏在寄主体内和种苗上,或以分生孢子附着在病残体上越冬。翌年,菌丝产生新的分生孢子,借风、雨水传播蔓延,从植株的气孔、伤口侵入。一般在温暖多湿条件下,尤其是连阴雨后发病重。植株因缺肥生长不良,或受风害和葱蓟马等危害严重时发病较重。
1. The main characteristics of the occurrence of diseases (1) Purple Onion green onion purple spot disease, also known as black spot, is a common disease onion, the disease is mainly affected leaves and peduncles, but also harmful bulbs. Lesions and more from the tip of the middle of the pedunculate or pedunculate, spread to the bottom after a few days. Lesions at the onset of small, gray to light brown, central purple. After the rapid expansion to an oval or spindle-shaped, depression, dark purple, black spots on the health students often form concentric wheel pattern. Lesions often expand to the whole leaf, or around the pedicel a week, so that leaves and pedicel fold. Appropriate environmental conditions, causing a large number of dead leaves, seriously affecting the yield and quality of green onions. Seed stalks harvested, susceptible to seed maturation. Pathogens lurk in mycelium and seedlings in the host, or conidia attached to the sick on the winter. The following year, hyphae produce new conidia, the wind, spread of rain spread from the plant’s stomata, wound invade. Generally warm and humid conditions, especially after the onset of heavy rain. Plants due to poor growth and lack of fertilizer, or by wind and thrips and other serious harm when the incidence of severe.