Abstract
A sequential sampling procedure for classifying the ratio of prey/predators with respect to a critical ratio was developed. This procedure was combined with a sequential density classification procedure for use in sampling European red mite ( Panonychus ulmi (Koch)) and a phytoseiid predator, Typhlodromus pyri (Scheuten) in New York apple orchards. Use of the sequential procedure would result in ≥40% savings in sample size for many prey and predator densities. Frequencies of erroneous classification were similar for the sequential procedure and a fixed sample size procedure that used the maximum number of samples that might be taken when using the sequential method. To use the sequential ratio classification procedure, variance-mean models for the prey and predator are required as well as knowledge of the correlation between these two populations. Sensitivity analysis showed that the procedure, as applied to European red mite and T. pyri , is robust with respect to variation in this correlation.
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