松突圆蚧防治指标的研究

STUDIES ON POPULATION DYNAMICS AND ECONOMIC THRESHOLD OF THE PINE NEEDLE HEMIBERLESIAN SCALE

本文旨在探讨制定松突圆蚧(Hemilerlesia pilysophila Takagi)防治指标的方法.根据虫害发生特点,从个体及群体两种水平进行了研究.个体危害程度可分为4个等级,结果表明Ⅱ至Ⅳ级不同树冠层的虫口密度呈有规律变化,虫口密度随危害程度增大而减小;Ⅲ级后材积连年生长量显著下降,Ⅳ级超过极显著水平.在群体(即林分)水平来看,稔山平均虫口密度明显高于寨场山.以林分受害指数作为群体受害程度的测度.惠东县寨场山、稔山及海丰县圆墩平均受害指数分别为37.49％、28.42％和33.95％.调查数据表明,林分材积损失率随林分受害指数变化大致为一条Logistic曲线,通过计算机拟合,得林分材积损失率的估测模型.根据防治指标定义和估测模型推导出寨场山、稔山及圆墩3种立地类型的防治指标依次为34％、47％及30％(以受害指数表示),由经济为害水平(EIL)定义出发,我们得到相应的3种防治决策函数.

This paper tried to inquire into the method of formulating economic threshold of the pine needle hemiberlesian scale. On the specialities of pest infection they were reseached in two levels of individuals and population of trees. Damage degrees of individuls were divided into four classes. The results showed that the pest density in different crowns from class Ⅱ to class Ⅳ was regularly variable and it decreased with the increasxe of damage degrees. The current annual increment of volume was largely reduced in class Ⅲ & Ⅳ . In the level of population of trees (i. e. stand) mean density of pest insect in Nian Shan was much higher than that in Zhai Chang Shan. The index of damage of stand was regarded as the measurement of stand losses. The mean index or damage of stand in Zhai Chang Shan, Nian Shan and Yuan Dum was respectively 37. 49%, 28. 42% and 33. 95%. From the data surveyed the volume damage rates showed a Logistic curve as the index of damage changed. Predictive models of volume damage rates were constructed by means of computer. According to the definition of ECONOMIC THRESHOLD (ET)and predictive models, ET was ogtained in Zhai Chang Shan, Nian Shan and Yuan Dun. They were 34%, 47% and 30%. We also got the functions of decision malting from the definition of ECONOMIC INJURY LEVEL (EIL) in viewpoint of economics.