van der Werf
First author: Department of Entomology, Cornell University, NYSAES, Geneva, NY 14456; second author: 1 Findlay Avenue, Ottawa, Ontario K1S 2T8 Canada; and third author: Department of Theoretical Production Ecology, Wageningen Agricultural University, Bornsesteeg 47, Wageningen, 6708PD, the Netherlands
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Accepted for publication 13 July 1999.
Guides for making crop protection decisions based on assessments of pest abundance or incidence are cornerstones of many integrated pest management systems. Much research has been devoted to developing sample plans for use in these guides. The development of sampling plans has usually focused on collecting information on the sampling distribution of the pest, describing this sampling distribution with a mathematical model, formulating a sample plan, and sometimes, but not always, evaluating the performance of the proposed sample plan. For crop protection decision making, classification of density or incidence is usually more appropriate than estimation. When classification is done, the average outcome of classification (the operating characteristic) is frequently robust to large changes in the sampling distribution, including estimates of the variance of pest counts, and to sample size. In contrast, the critical density, or critical incidence, about which classifications are made, has a large influence on the operating characteristic. We suggest that rather than investing resources in elaborate descriptions of sampling distributions, or in fine-tuning sample size to achieve desired levels of precision, greater emphasis should be placed on characterizing pest densities that signal the need for management action and on designing decision guides that will be adopted by practitioners.
© 1999 The American Phytopathological Society