Five phytoseiid mite species: Phytoseiulus persimilis Athias-Henriot, Neoseiulus californicus McGregor , Neoseiulus womersleyi Schicha , Amblyseius eharai Amitai and Swirski, and Euseius sojaensis Ehara Acari: Phytoseiidae were collected from commercial Japanese pear orchards in Shizuoka Prefecture. To evaluate the suppressive effect of generalist phytoseiid species on the spider mite Tetranychus kanzawai Kishida Acari: Tetranychidae , we compared four treatments E. sojaensis release, A. eharai release, synthetic pyrethroid application, and no-release performed in a greenhouse. These treatments were conducted when T. kanzawai densities were low, and pine pollen was provided as alternative food for predatory mites in all treatments. At late June, the peak densities of T. kanzawai were significantly low in E. sojaensis release and in no-release compared with in pyrethroid application and in A. eharai release. The dominant phytoseiid species in E. sojaensis release and in no release was E. sojaensis. After July, however, E. sojaensis densities became lower in E. sojaensis release as well as no-release, and thus T. kanzawai densities became higher in all treatments at early August. These results suggest that conservation and augmentative release of E. sojaensis prior to T. kanzawai population increase, might suppress the outbreak of this spider mite in Japanese pear orchards until early summer.
Nesidiocoris tenuis Reuter has good potential as a biological control agent for tomato. In this study, we evaluated the withinplant distribution of N. tenuis in greenhouse grown tomatoes under an increasing temperature condition. When the population density of Bemisia tabaci Gennadius was low, N. tenuis aggregated on the upper leaves. However, when the population density of B. tabaci was increased on the middle leaves, N. tenuis also increased on the middle leaves. These results suggest that N. tenuis are capable of aggregating in an area where B. tabaci are distributed and preying on them. However, we need to investigate not only the increasing temperature condition but also the decreasing temperature condition to prove N. tenuis changes its within-plant distribution depending on prey density.
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