Sampling western spruce budworm larvae by frequency of occurrence on lower crown branches.

Abstract

A sampling method was derived whereby budworm density can be estimated by the frequency of occurrence of larvae over a given threshold number instead of by direct counts on branch samples. The model used for converting frequencies to mean densities is appropriate for nonrandom as well as random distributions and, therefore, is applicable to all population densities of budworm. The method is suggested as a possible alternative to the direct counting of larvae in lower crown sampling.

Citation

Mason, R.R.; Beckwith, R.C. 1990. Sampling western spruce budworm larvae by frequency of occurrence on lower crown branches. Res. Note PNW-RN-497. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 12 p