Two-Stage Cluster Sampling for Pine Tip Moths

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Abstract
Techniques are discussed for sampling immature stages of pine tip moths, Rhyacionia spp. (Lepidoptera: Tortricidae, Olethreutinae), on young trees. Sampling is described for all immature stages of the Nantucket pine tip moth, R. frustrana (Comstock), and the pitch pine tip moth, R. rigidana (Fernald), on 3-year-old loblolly pine, Pinus taeda L., in the Georgia piedmont. Some new biological observations are given to aid in the examination of collected shoots for the location of the immature stages. Two-stage cluster sampling was employed. The first stage is the random selection of sample trees; the second stage involves vertical stratification of the trees and the random subsampling of shoots from these strata. Field procedure is detailed. Statistical formulae are presented for estimating the numbers of individuals per shoot, per tree, and per ha, with respective estimates of variance. Estimation of gain in precision due to stratification is discussed. A technique is presented to determine the optimum numbers of trees and shoots to sample to obtain a specified precision at a minimum cost.

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