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中湾林区天然油松林于一九六七年发生球果螟、松梢螟、球果小卷叶蛾与松梢小卷叶蛾四种枝梢、球果害虫危害。其中以球果螟数量最多,为害尤烈,此后,除一九七○、一九七一两年,每年都大发生,种籽产量及树木生长均遭到很大损失。据今年七月调查,二十二年以上的中龄树,球果几乎全部被害,新梢受害率达47％;十年生幼树球果受害率高达69％。八只窑天然油松林面积3744亩,正常年分可采种两千余斤,一九七六年因虫害严重,仅采得五
In 1969, the natural Pinus tabulaeformis forest in Zhongwan forestry suffered from four kinds of shoots, conchocarp and conchocosmus, including the fruit borer, the pine needle borer, the small leaf roller and the pine leaf roller. Among them, the highest number of borer borer, the damage is especially intense, since then, except in 1970, 1972, annual occurrence, the seed yield and tree growth have suffered a great loss. According to a survey conducted in July this year, most of the middle-aged trees and cones over 22 years old were killed. The damage rate of new shoots reached 47% and that of perennial young tree cones reached 69%. Eight kilns natural pine forest area of 3744 acres, the normal year can be collected more than two thousand kilograms, due to serious pests in 1976, only made five