甘薯田斜纹夜蛾空间格局及抽样技术研究

Spatial Distribution Pattern of Larva of Prodenia Litura(Fabricius) in Sweet Potato Fields

为了揭示斜纹夜蛾在甘薯田的空间分布格局,2010年对斜纹夜蛾不同发生密度的甘薯田块进行了调查,取得了8组样本资料,运用多种聚集度指标、Taylor的幂法则以及Iwao的m*-m直线回归方程进行统计和分析。结果表明:斜纹夜蛾的卵块为均匀型分布;幼虫呈聚集分布型,分布的基本成分是个体群。田间虫口密度高低影响空间分布,虫口密度加大,斜纹夜蛾幼虫数量差异变小。并利用Blackith种群聚集均数(λ)分析了其聚集原因,当m<4.424 1头.株-1时,其聚集是由于某些环境如气候、土壤湿度、植株生长状况等所致;当m>4.424 1头.株-1时,其聚集是由于害虫本身的群集行为与环境条件综合影响所致。同时,建立了斜纹夜蛾幼虫在甘薯上的理论抽样数公式[N=t2/D2(3.9180/m+1.8426)],给出了不同误差、不同密度条件下的理论抽样数,并列出了序贯抽样公式[T0(n)=0.5n±3.0488槡n]。

Occurrence of Prodenia litura in sweet potato fields was investigated in 2010 in order to reveal their distribution.Eight groups of samples were obtained.Several clustering indices,power law of Taylor and Iwao＇s way（regressive relation by m＊-m） were used to test the spatial distribution pattern of P.litura in sweet potato fields.The results showed the eggs of P.litura fits the pattern of symmetrical distribution,and the larva of P.litura fits the pattern of aggregative distribution in sweet potato fields with the basic component of distribution of colony.The population density effected the Spatial distribution.The cause of their aggregation was tested by Blaekith＇s method,when m4.424 1,their aggregation was caused by some environmental factors such as climate,soil humidity,and growth and so on;when m4.424 1,their aggregation was caused by their behavior and environmental conditions.Based on the data of the spatial distribution,the model for determining the optimum theoretical sampling number model [N=t2/D2（3.9180/m＋1.8426）] and the optimum sequential sampling model [T0（n） = 0.5n±3.0488] were proposed.