Accuracy of a Single 30-stem Sample for Detecting Alfalfa Weevil Larvae (Coleoptera: Curculionidae) and Making Management Decisions

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Abstract
Management decisions in many alfalfa integrated pest management programs are based on a single 30-stem sample estimate of the alfalfa weevil, Hypera postica (Gyllenhal), larval population. Repeated 30-stem samples were taken from five fields under a variety of stand conditions over a 2-yr period to calculate the variance/mean relationship with Taylor’s power law. A computer simulation was used to estimate the proportion of single-sample estimates that underestimate (fail to spray) or overestimate (spray unnecessarily) a known population mean in relation to an economic threshold. Management-decision errors were found to increase significantly as the population mean neared the threshold.