Capability of Scolothrips takahashii (Thysanoptera: Thripidae) as a control agent of Tetranychus urticae (Acari: Tetranychidae) for protecting strawberry plug plants in summer

To evaluate whether the predatory thrips Scolothrips takahashii Priesner can be used as a control agent of the two-spotted spider mite Tetranychus urticae Koch at strawberry nurseries in summer, we examined the effects of releasing S. takahashii on populations of T. urticae. Twelve plots, each consisting of seven strawberry plants with 30 adult T. urticae females on each, were placed in an experimental greenhouse. Plots were randomly allocated to four treatments: adult S. takahashii females released at the ratio of 30:1 (number of T. urticae:number of S. takahashii); adult S. takahashii females released at the ratio of 10:1; adult females of the phytoseiid mite Phytoseiulus persimilis Athias-Henriot released at the ratio of 30:1; and no natural enemy released (control). In both S. takahashii release treatments, T. urticae numbers decreased to almost zero within 24 days and were significantly lower than those in the control treatment at 14 days; the decreasing pattern of T. urticae populations in these two experimental treatments was similar to that seen with P. persimilis release. These results suggest that S. takahashii can be an effective control agent against T. urticae in integrated pest management programs to protect strawberry plug plants in summer.