The succession of phytophagous and phytoseiid species in a newly planted apple orchard without insecticide applications

概要

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Population dynamics of phytophagous and phytoseiid mites in a newly planted apple orchard were investigated for the consecutive 5 years just after the stop of insecticide applications, to verify the effect of the phytoseiids on the dominance and density of phytophagous mite species. Phytoseiid mites were typically most abundant in autumn from 2005 to 2008, except in 2009 when there were two marked peaks. Although 10 phytoseiid mite species were collected over the five-year study period, species abundance and composition changed gradually over time. The phytophagous mites were most abundant in the autumn of 2005, but the timing of peak occurrence and density changed as the study progressed. Changes in the abundance and species composition of the phytoseiid mite communities, Tetranychus urticae abundance was not suppressed by the phytoseiid mites. Although Panonychus ulmi was suppressed to insecticide application, P. ulmi may affect T. urticae abundance under a no-insecticide regime. Finally, T. urticae disappeared and P. ulmi and Aculus schlechtendali decreased in abundance. Although not marked, Typhlodromus vulgaris played a key role in affecting the stability of mite communities in apple orchards when no insecticides were applied.