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Spatial distribution and population fluctuation of Tetranychus urticae and its predator Phytoseiulus persimilis in a rose greenhouse

عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is a serious pest of many greenhouse crops such as bean, cucumber, rose and many others. The control of spider mites has been mainly based on the use of acaricides. The wide use of acaricides is of environmental concern and has developed acaricide resistance in mites. Phytoseiid mites are used for biological control of pest mites. This study aimed to determine population fluctuation and spatial distribution pattern of T. urticae and its predator Phytoseiulus persimilis Athias-Henriot (Phytoseiidae) on four rose varieties (Avalanche, Dolce vita, Samurai and Sorbet) under greenhouse conditions. Motile stages (combined adults and juveniles) and eggs of T. urticae and P. persimilis were counted on a leaf weekly using a hand lens. The sampling was carried out randomly and the leaves of a rose plant were taken from the canopy base (shoots bent over beds), the middle of the canopy (area between base and top) and the top (flowering shoots), which summed a total of 30 leaves. Taylor's power law method was used to estimate the spatial distribution pattern of both prey and predator. From 6th September 2016 to 22th April 2017, T. urticae and P. persimilis showed aggregated distribution patterns during the sampling dates. According to the results, the highest population density of T. urticae per leaf was recorded on Samurai (14.90.84) and the lowest population density was observed on Dolce vita (5.250.48). A synchronous behavior between both predator and prey was observed in the four varieties tested. Also a decreasing trend was observed in T. urticae population by increasing the number of P. persimilis so that after 16 weeks, the population of T. urticae on all mentioned varieties decreased to the minimum density near zero. It was concluded that P. persimilis is so efficient in controlling T. urticae under greenhouse conditions.
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