A SAMPLING SYSTEM FOR EGGS OF WESTERN BLACKHEADED BUDWORM, ACLERIS GLOVERANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE), ON WESTERN HEMLOCK, TSUGA HETEROPHYLLA (RAF.) SARG.

Abstract

AbstractEggs of western blackheaded budworm, Acleris gloverana (Walsingham), are laid on the lower surface of western hemlock, Tsuga heterophylla (Raf.) Sarg., needles. A comparison was made of the following measures of sample branch size as a basis for expressing egg density: fresh branch weight, branch area, total twig length, branch volume, and number of buds. The criteria for selection of these measures were as follows: correlations of branch size with dry needle weight, variances of egg density and their relative contribution to sample size, and ease of measurement. Fresh branch weight was the best choice. A sequential sampling system was developed on this basis and was related to a scale of predicted defoliation. In addition, a transformation was provided for use in data analysis.