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苹果实生砧木幼苗期突然枯死,是由一种叫做立枯丝核菌侵染实生苗基部或幼根造成的,称之为苗木立枯病。通常幼苗出土后,生长至2片真叶期发病最姒。病株子叶先行萎蔫,尔后逐渐干枯,胚轴部分呈烫伤状水烂,根部淡褐色,有白色棉絮状菌丝层。一般地势低洼、排水不良、土壤粘重、植株过密及前茬花生或蔬菜地发病重,严重时死苗率高达15％以上。当幼苗嫩茎半木质化后、病害停止发生。因此,应掌握在幼苗嫩茎半木质化前防
Apple rootstock seedlings suddenly died of seedlings, is called a Rhizoctonia Rhizoctonia infected seedlings caused by the base or young roots, called the seedling blight. Usually after the emergence of young seedlings, the growth to 2 true leaves of the disease the most common disease. Cotyledons diseased cotyledons first, and then gradually dry, scalded part of the hypocotyl water rotten roots light brown, with white cotton-like mycelium. Generally low lying, poor drainage, soil sticky, too dense plant and the former crop peanut or vegetable disease, serious dead seedling rate as high as 15%. When seedling sprouts half-lignified, the disease stops happening. Therefore, should grasp the seedlings of young stem half-lignification of the prevention