落叶松绶尺蠖的防治指标

POPULATION INDEX FOR CONTROL OF ZETHENIA RUFESCENTARIA MOTSCH.

分别对落叶松绶尺蠖危害程度不同的林分进行了研究，其结果：在郁闭度为０．９、０．８的３８和３９年生的落叶松林内，平均每株针叶量分别为３．９７５５ｋｇ和４．３５３０ｋｇ；当落叶松失叶量在５０％、７５％、１００％时，其材积损失分别为０．００２２、０．００５１、０．００７４ｍ３／株；损失率分别为２８．５７％、６１．４５％、８５．８８％；落叶松绶尺蠖幼虫的防治指标理论值为３１６．０１头／株；按失叶量５０％的防治标准时，其郁闭度０．８的林分防治指标为３１８．９５头／株，郁闭度０．９的林分防治指标为２９１．２９头／株。

The larch stands damaged by Zethenia rufescentaria Motsch. in varying degree was studied. The total weight of needles per tree was 3.9755kg in 38-year-old larch stands with 0.9 crown density, and that in 39-year-old larch stands with 0.8 crown density was 4.3530kg. The measuring results showed that while a tree lost 30%, 75% and 100% of needles, the growth loss in volume was 0.0022m 3, 0.005m 3 and 0.0074m 3, respectively, or 28.57%, 61.45% and 85.88% loss rate. Theoretical value by density for control of Z.rufescentaria was 316.01 larvae per tree. Taking 50% of needles as a warning level, the density index for control of this pest in the larch stands with 0.8 and 0.9 crown densities was 318.95 larvae /tree and 291.29 larvae /tree, respectively.