一、危害症状及发病原因 板栗立枯病发生相当普遍,系苗期主要病害。一般幼苗出土后尚未木质化,根茎部出现褐色长形病斑,逐渐向上下蔓延,最后病部凹陷,病皮变黑色。受病害部以下根部组织正常,地上部叶片失水枯萎。 发病原因,主要是苗圃选择不当,生态环境条件差,如苗圃土壤粘重、通气性差、低湿易涝、排水不良的地块;以及施肥不合理,使用未充分腐熟的有机肥或氮肥过量等原因,致使苗根生长过弱被立枯病菌侵 First, the risk of symptoms and causes of chestnut blight is quite common, Department of seedling disease. General seedlings have not yet been lignified after the excavated, rhizome appear brown long lesions, gradually spread up and down, the final diseased part of the diseased skin black. Under the Ministry of the Ministry of disease under the normal root tissue, dry leaves above the ground wilt. The causes are mainly the improper selection of nursery, poor ecological and environmental conditions, such as sticky soil in nursery, poor aeration, low humidity and waterlogging and poor drainage; and irrational use of fertilizers, excessive use of under-matured organic fertilizers or excessive nitrogen fertilizer , Resulting in weak growth of seedling is infested by Rhizoctonia solani