2019 Volume 2019 Issue 66 Pages 100-105
From March 2016 to March 2017, we investigated seasonal population dynamics of the exotic predatory mite, Phytoseiulus persimilis estimated to have colonized tea fields in Shizuoka Prefecture, Japan. Species of phytoseiid mites in the tea field investigated were P. persimilis, and native species: Amblyseius eharai, A. obtuserellus, Neoseiulus womersleyi, and Euseius sojaensis. The percentage of P. persimilis in the species composition were 5.6% (2 Jul.) and 26.0% (6 Sept.). P. persimilis adults with eggs were found on 23 Mar for the first time. The two peaks of occurrences were observed on 25 Apr. three weeks after the peak of Tetranychus kanzawai, and on 23 Aug. two weeks after the peak of T. kanzawai. P. persimilis was not observed after the middle of Sept.. Primary dominant species of native phytoseiid mites was A. eharai, they occurred during most of the seasons. The peaks of native phytoseiid mites were observed on 24 May and 9 Sept., after the peaks of P. persimilis. Indices of ω proposed by Iwao (1977) which indicates a special association between two species were calculated among T. kanzawai, P. persimilis and Amblyseius spp. The indices between T. kanzawai and P. persimilis changed plus (coexistence distribution) to minus (exclusion distribution) around Apr. - May. These results suggest that P. persimilis strongly depends on T. kanzawai, while P. persimils does not significantly affect the populations of native phytoseiid mites in tea fields.
