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1983年选择7月下旬花铃期受红叶螨为害的棉田,按棉株受害程度分为三个等级:全株近二分之一叶片发生黄红斑为Ⅰ级;二分之一至全部叶片发生黄红斑为Ⅱ级;超过二分之一以上叶片发生黄红斑,并有落叶出现为Ⅲ级.每级定45株棉花,喷洒杀螨剂(20%双甲脒1:1000倍).定期调查蕾铃数量,分别收花比较产量.同时,每期选取有代表性的棉株每级三株,测定叶片总面积和根茎叶、蕾铃的干
In 1983, the cotton fields damaged by Tetranychus urticae in the flower-boll stage in late July were divided into three grades according to the degree of damage of the cotton plants: nearly half of the whole plant had yellow erythema for the first grade; one-half to all the leaves occurred Yellow erythema grade Ⅱ; more than half of the leaves yellow erythema, and deciduous appear as Grade 3. Each level set 45 cotton, spraying acaricide (20% amitraz 1: 1000 times) .Regular investigation The number of bolls, respectively, compared with the yield of flowers.At the same time, each selected three representative cotton plants at each level, the total area of leaves and rhizomes, leaves dry