Simulation studies of binomial sampling: a new variance estimator and density predictor, with special reference to the Russian wheat aphid (Homoptera: Aphididae)

Standard methods of obtaining absolute population estimates for the Russian wheat aphid, Diuraphis noxia (Mordvilko), are not feasible because of the insect's small size, aggregated distribution, and difficulty in handling the samples. Because presence-absence information can be obtained easily, prediction of population density based on the proportion of sample units uninfested by the organism (Po) was investigated. Data on sample density (m) and Po for the Russian wheat aphid were obtained weekly in two winter wheat fields. The relationships between ln(m) and ln(-ln Po) and between ln(s2) and ln(m) were determined by regression. Several different published formulae for density predictions and their variances using the above regressions were examined analytically. New density predictor and variance estimators were developed and shown through simulation to be superior to existing estimators