Spatial distribution pattern of Tetranychus urticae and its egg predator Scolothrips longicornis on different bean cultivars

Abstract : Bionomics of two-spotted spider mite, Tetranychus urticae Koch, and its egg predator Scolothrips longicornis Priesner was studied in the southeast of the Tehran province, Varamin from 11th July to 22th September 2010 on six bean cultivars including Goli, Akhtar, Sadaf, Parastoo, Talash and Baker. The mean population densities of the overall life stages of T. urticae and S. longicornis per leaf on Goli (36.27 and 2.87, respectively) were significantly more than other cultivars. The spatial distribution of T. urticae and S. longicornis was determined by the following four methods: index of dispersion, Lloyd's mean crowing, Taylor's power law and Iwao's patchiness regression, whereas Morisita's coefficient of dispersion was calculated for T. urticae on different crops. The index of dispersion, Morisita's index and Lloyd's mean crowding indicated an aggregated pattern for spatial distribution of this mite and their predator on all bean cultivars. The spatial distribution pattern of T. urticae and S. longicornis using Taylor's power law and Iwao's patchiness in most cases was aggregated and in few cases random. The linear regression between the predator and prey population densities indicated a density-dependant predation by S. longicornis on T. urticae. Spatial distribution parameters of two-spotted spider mite and its predator can be used to outline a sampling program, estimate population density of these mites and efficiency of the predator for using in IPM programs
Keyword : Tetranychus urticae, Scolothrips longicornis, population density, spatial distribution, density dependence interaction, optimum sample size
Author(s) : , H. Pakyari
Downloads : 1198


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