Determining Population Characteristics and Sampling Procedures for the Western Flower Thrips (Thysanoptera: Thripidae) and the Predatory Mite Amblyseius cucumeris (Acari: Phytoseiidae) on Greenhouse Cucumber

Abstract

Distribution characteristics of the western flower thrips, Frankliniella occidentalis (Pergande), and the predatory mite Amblyseius cucumeris (Oudemans) were studied on greenhouse cucumber and used in developing presence–absence sampling procedures. The variance-mean relationship was described by Taylor's power law and resulted in aggregation indices on middle leaves of 1.62 for thrips larvae and 1.31 for thrips adults and A. cucumeris. Tables are presented for estimating population density from percentage of leaves infested and for determining sample size required at different population densities and precision levels. Thrips density correlated with leaf damage but not with fruit damage.