SPATIAL-DISTRIBUTION AND SAMPLING PLANS FOR 4 SPECIES OF CEREAL APHIDS (HOMOPTER, APHIDIDAE) INFESTING SPRING WHEAT IN SOUTHWESTERN IDAHO

Taylor's power law was used to model relationships between mean densities (per tiller) and variances for four cereal aphids-Diuraphis noxia (Mordvilko), Metopolophium dirhodum (Walker), Sitobion avenae (F.), and Schizaphis graminum (Rondani)infesting spring wheat in southwestern Idaho. Model slopes were > 1.0 for all species, which indicated that the aphid species all showed aggregated spatial patterns. The spatial pattern of D. noxia was significantly more clumped than those of the other three species. No differences among years were found in the aphid species' degree of aggregation. Taylor's power law parameters were used to generate numerical (complete count) sample size curves for each aphid species. Parameters from the regression of ln(mean density) on ln[-ln(proportion of wheat tillers with no aphids)] were used to develop a functional relationship between mean density and proportion of empty sample units, and binomial (presence-absence) sample size curves for each aphid species.