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The current study was conducted to develop a cost-effective and reliable method to estimate population densities of 1st-instar bag worms, Oiketicus kirbyi (Guilding), in Costa Rican oil palm plantations. Total numbers of larvae per tree were correlated with numbers on 80, 160, 240, or all (320--360) folioles of all palm leaves. The r2 values of these correlations were used to assess the accuracy of population estimates obtained by sampling leaves in different positions within the palm crown or different numbers of folioles per leaf. Larvae were most abundant on apical and subapical foliolesof leavesin the upper palm crown. When a limited number of folioles per leaf (80, 160, or 240) was sampled, leaves in the upper crown provided the most accurate estimates of larval densities per tree. Decreasing accuracy of population estimates from upper to lower leaves resulted from increasing variability of larval proportions from upper to lower leaves. Larval populations of 2 other oil palm defoliators, Opsiphanes cassina (Felder), and Stenoma cecropia (Meyrick),are currently assessed by sampling leaf 17. Sampling O. kirbyi larvae on 160 foliolesof leaf 17, in the middle palm crown, may represent an acceptable compromise among cost-efficiency,reliability,and simultaneous assessments of several defoliatingcaterpillars. Reasonablyaccurate estimates of larvaldensities per area obtained in this study by sampling 1 palm per hectare should not be interpreted as a general recommendation for sample size, because the effect of population density on optimal sample size per hectare remains yet to be investigated.
Document Type: Research Article
Publication date: April 1, 1996
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.