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在围场县境内为害针叶树的主要害虫松毛虫有落叶松毛虫和油松毛虫,以前者为主。每年集体林发生松毛虫面积在6—7万亩左右。据树木解析,生长正常的油松每亩每年平均立木材积生长量为0、22848立方米,因受松毛虫为害,即每年每亩平均立木材积生长量仅为0.13243立方米,每年每亩减少立木材积生长量0.09605立方米。全县受松毛虫危害面积(针叶被吃完50％以上)按25000亩计算,年损失
The main pests of coniferous trees damaged in Weichang County were Dendrolimus caterpillars and Dendrolimus punctatus, mainly on the former. Dendrolimus occurred in collective forests in an area of 6-7 million mu each year. According to the tree analysis, the average growth volume of pine oil per mu per year is 0,22848 cubic meters. Due to the damage caused by pine caterpillars, the average annual volume of timber per mu per year is only 0.13243 cubic meters, Volume growth of 0.09605 cubic meters. The area affected by pine caterpillars (conifers were eaten more than 50%) by 25000 acres, the annual loss