Implementation of Sequential Sampling Plans for Gypsy Moth (Lepidoptera: Lymantriidae) Egg Masses In Eastern Hardwood Forests

Abstract

Sample units (timed walks and fixed-radius plots) used for determining gypsy moth, Lymantria dispar L., egg mass density were evaluated for use in area-wide IPM programs in southeastern Appalachian hardwood forests. Timed walks, a measure of egg masses per unit time, were significantly related to egg masses per unit ground area, but the relationship was inconsistent among habitats and individuals. Normalized residuals from the regression of timed-walk estimate on egg mass densities from fixed-radius plots showed a spatial dependence. This spatial dependence demonstrated that the regression was inconsistent among participating government agencies within an IPM demonstration project. Egg mass counts from fixed-radius plots were fit to a negative binomial frequency distribution. A computer spreadsheet was developed and used interactively to create sequential sample plans using this distribution and inputs of thresholds and acceptable error rates from managers. Validation studies were conducted on two sequential sampling plans within 132 l-km2 cells. The sequential sampling plans gave the same pest management decision as fixed-sample size plans in 79-84% of the cells, recommended additional samples in 7-19% of the cells, and gave incorrect pest management decisions in 2-3% of the cells.