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Spatial Distribution and Sampling of Icerya purchasi Mask. (Hom.: Margarodidae) on Orange Trees in Southwest Iran

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Author(s): Mehdi Esfandiari | Mohammad Saeed Mossadegh

Journal: Journal of Biological Sciences
ISSN 1727-3048

Volume: 7;
Issue: 7;
Start page: 1239;
Date: 2007;
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Keywords: sampling plan | spatial distribution | Icerya purchasi | southwest Iran

ABSTRACT
The Cottony-Cushion Scale, Icerya purchasi Maskell, is an important pest of citrus and ornamentals. The first objective of this study was to analyze the spatial distribution of this insect on the orange trees, in southwest Iran. The second objective was to develop sampling plans to determine sample sizes for fixed levels of precision and fixed-precision-level stop lines for sequential sampling. Population estimates were made by registering the number of various stages of the scale on 40 twigs at 10 days intervals from 2003 to 2004. Taylor`s power law and Iwao`s patchiness regression were used to analyze the spatial distribution of the pest. Taylor`s power law fitted the data better (R2 = 0.80) than Iwao`s regression model (R2 = 0.72), indicating that I. purchasi populations were aggregated. Optimal sample sizes for fixed precision levels of 0.10 and 0.25 were estimated with Taylor`s regression coefficients. Required sample sizes increased dramatically with increased levels of precision. The sampling plans presented should be a tool for research on population dynamics and pest management decision.
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