Cereal Aphid Populations in Winter Wheat: Spatial Distributions and Sampling with Fixed Levels of Precision

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Abstract
Taylor's power law and Iwao's patchiness regression were used to analyze spatial distributions of four aphid species, Schizaphis graminum (Rondani), Macrosiphum avenae (F.), Rhopalosiphum padi (L.), and R. maidis (Fitch), in 0.3-m samples taken from winter wheat fields. Taylor's power law generally provided a better description of variance/mean relationships for the species than did Iwao's patchiness regression. All species exhibited aggregated patterns of spatial distribution, but patterns of distribution differed among some species. Sample size requirements for fixed levels of precision and sequential sampling plans of fixed levels of precision were determined by utilizing estimated variance/mean relationships obtained from Taylor's power law regressions. Sample size requirements for estimation of population means with fixed levels of precision were greatest for R. padi, and decreased in the order M. avenae, S. graminum, and R. maidis.