Abstract
Species composition, population dynamics of spider mites (Panonychus ulmi (Acari: Tetranychidae) (Koch) and Tetranychus urticae Koch (Acari: Tetranychidae)) and predaceous mites (Amblyseius andersoni (Chant) (Acari: Phytoseiidae) and Zetzellia mali (Ewing) (Acari: Stigmaeidae)) were studied for eight months each year (March-October) during 2005-2007 at two localities with different intensities of pesticide use. Using Berger-Parkers dominance index and Sorensons coefficient, the index of dominance and predator-predator, predator-prey, and prey-prey associations were defined among each of these species to determine changes in species compositions and population densities and comprehend the influence of pesticide use in pest management on populations of spider and predatory mites in apple orchards. Sorensons coefficient helped to measure the intensity of positive, neutral, or negative interspecific associations for each species and Berger-Parkers dominance index clarified the dominance of specific species. During 2005 the dominant species in both localities was P. ulmi, but during 2006-2007 at one locality both species of spider mites showed almost equal dominance. The results of Sorensons coefficient confirmed that there was significant predator-prey association among P. ulmi and A. andersoni and P. ulmi and Z. mali, and prey-prey association between P. ulmi and T. urticae in both localities. The analysis of the population dynamics showed delayed occurrence of predatory mites compared with the spider mites, from 48 to 106 days for A. andersoni and 91 to 137 days for Z. mali depending on the research period and locality.