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山楂叶螨(Tetranychus viennesis Zacher)在苹果树上呈聚集分布。苹果树的螨量,以南方和东方为多,同方向的上、下部螨量差异不大。适宜的调查取样方法是:选有代表性的苹果树5株,每株在东下方或南下方随机取样5点,每点查10片叶,共计250片叶,汁算百叶螨量。三年田间试验表明,苹果产量损失率(Y)与百叶螨量(X)呈正相关(P<0.001)。亩产750公斤的苹果园,5～6月份防治山楂叶螨的经济阈值为:百叶成螨、若螨量450头,或为害指数0.8～0.9。
Tetranychus viennesis Zacher is aggregated in apple trees. The amount of mite in the apple tree is much larger in the south and east, and there is not much difference between the mite and the mite in the same direction. Appropriate survey sampling method is: Select a representative apple tree 5, each plant in the east or south under the random sampling of 5 points, check each leaf 10 points, a total of 250 leaves, juice counted Spider mite volume. Three-year field trials showed that there was a positive correlation between yield loss (Y) and leaf spider mite (X) (P <0.001). 750 kg per mu yield of apple orchards, from May to June prevention and control of hawthorn spider mite economic threshold: adult leaf mite, if the amount of mite 450, or damage index of 0.8 to 0.9.