柑桔粉虱在柚园的空间分布型及抽样技术

Studies on the Spatial Distribution Pattern of Dialeurodes citri in Grapefruit Garden and Sampling Techniques

经测定,柑橘粉虱在柚园的空间分布基本为负二项分布的聚集分布型,其中柚园内分布以个体间相互排斥为特征,新梢或基地内分布的主要成分是个体群即核心分布型。经种群聚集均数(λ)测定,其聚集原因是由种群自身特性与环境的异质性共同作用引起的,且λ随叶平均虫量的增加而呈直线增加。以每梢取基叶、中部叶、顶叶三叶,每株取东、南、西、北、中五个方位梢或任一梢,采用平行跳跃法或随机取样法调查虫情简易而准确。判断该虫发生程度的界限方程有2组,最多调查16或21株即能判断该虫的发生情况。

The spatial distribution pattern of Dialeurodes citri (Ashmead) in grapefruit garden generally shows a negative binomial distribution of aggregation, which is characterized with individual repulsion and predominant individual group as core distribution pattern in the crown of a tree or in the grapefruit garden. Through detection of λ value, the reason of aggregate is the species properties and the environmental difference , and λ value increases linearly with the increase of population density. The type of parallel and random sampling is easy and precise for investigating pest among the eastern, southern, western, northern and middle shoots or any shoot of a tree and among low-, mid- and top-leaves of a shoot. There are two equations to judge the occurrence degree of the Dialeurodes citri. The pest's occurrence degree can be judged by investigating 16 or 21 trees at most.