Cray leaf spot of maize, caused by Cercospora zeae-maydis, became one of the most serious foliar and significant yield-limiting diseases of maize in Yunnan province. According to the field surrey and artificial inoculation, the disease occurred from early June to late-July, and became rapidly epidemic in mid-August to late-September with maize tasseling and maturing. Disease severity was different depending on altitudes. The pathogen overwintered in the infected com residues remaining on the soil surface. The resistant cultivars accounted for only IS. 78 %. The average temperature over 20 X. And relative humidity over 80 % were favorable for the disease development. Early-planting could reduce the disease severity.%灰斑病是云南省玉米叶部病害之一,严重地制约着玉米产量.通过田间定点系统调查和人工接种鉴定,证明云南省玉米灰斑病的始发期为6月上旬至7月下旬,在玉米抽雄吐丝至成熟期的8月中旬至9月下旬迅速暴发流行.同一品种随着海拔增高病情加重,特别是在海拔1800 m以上,产量损失最大.海拔1500 ～ 1800 m区域次之,海拔1500 m以下区域发病较轻.病原菌主要以分生孢子在地表的病残体上越冬.抗病品种少,中抗以上品种仅15.78％.日平均气温在20℃以上,相对湿度80％以上,有利于病害的发生.提早播期有减轻病害的作用.
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