Spatial Distribution Pattern and Application of Fourth-Generation Mature Larvae of Cotton Bollworm(Helicoverpa armigera Hübner) in Corn Field

[Objective]The paper was to study the spatial distribution pattern of fourth-generation mature larvae of cotton bollworm in corn field. [Method] The plots with different occurrence densities of fourth-generation cotton bollworm were investigated from August to September in 2009. Six groups of sampling data were obtained, and seven indicators including aggregation index method, Iwao method and Taylor method, etc. were used to determine its spatial distribution pattern. [Result] Aggregation index test showed that in all plots, Moore I0, Lloyod m*/m1, Kuno Ca0, diffusion coefficient C1, diffusion index Iδ1, negative binomial distribution K0, indicating that mature larvae of cotton bollworm showed uniform distribution in summer corn. Iwao regression equation of fourth-generation mature larvae of cotton bollworm in summer corn was m* =0.090 6+0.766 9 m, r=0.986 3, indicating that the basic components of cotton bollworm distributed was single individual, and mature larvae of cotton bollworm in summer corn showed uniform distribution. The optimal sampling number of fourth-generation mature larvae of cotton bollworm in corn under different population densities could be calculated using formula N1=(1.090 6/m-0.233 1)/D2. [Conclusion] The result provided basis for accurate evaluation of population quantities and variation law of cotton bollworm, as well as prediction and control of the pest.