Populatioon density and spatial distribution pattern of Tetranychus urticae Koch on four different bean varieties namely Talash (Colorado-bean), Sadaf (Navy-bean), Goli (Kidney-bean) and Parastoo (Black-eye-bean) were determined in Tehran region during 2003. One leaf of bean crop was selected as a sample unit. By using the primary sampling, the reliable sample size with maximum relative variation of 20% was obtained to be 40 sample units. Variance to mean ratio as well as Taylor’s power law regression method were employed for determining the spatial distribution pattern of T. urticae. The rates of variance to mean ratio of T. urticae on Talash, Sadaf, Goli and Parastoo were assessed as 7.707, 6.938, 4.869 and 13.114, respectively. Regression method was employed for determining the spatial distribution in Parastoo variety only because non-significant regression was observed between the mean and variance in other varieties.The results revealed that the spatial distribution pattern of T. urticae on four bean varieties (using variance to mean ratio) was of aggregated type. The spatial pattern of mite on Parastoo variety using regression method was a random one. The maximum and minimum rates of T. urticae population density were determined on Talash and Parastoo varieties, respectively.
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