A SEQUENTIAL SAMPLING PLAN FOR ADULT TUBER FLEA BEETLES (EPITRIX TUBERISGENTNER): DEALING WITH “EDGE EFFECTS”

AbstractWe propose a sequential sampling plan for adult tuber flea beetles, Epitrix tuberisGent., in potato fields, which is based on a confidence interval calculated around a critical density value (Iwao 1975) and which uses Taylor’s Power Law (Taylor 1961) to estimate the variance. Because of the highly edge-biased gradients of density displayed by this insect, separate sequential expressions have been calculated for densities at the edges and centers of fields.In a survey of 12 commercial potato fields, spring-generation E. tuberisdensities in centers of fields were always far below the threshold level of one beetle per 10 plants employed at the time of sampling. The survey also indicated that fields that have been sown with potatoes for 2 consecutive years have higher beetle densities than fields sown with potatoes for a 1st year. Edge:center density ratios, however, were the same for the two categories of fields.