A new practical application of dipping strawberry plants in formulation oil to control Tetranychus urticae Koch（Acari: Tetranychidae）.

Abstract

In this study, we devised a new application for the control of Tetranychus urticae Koch, which infests strawberry plants, by dipping stems and leaves of strawberry plants in a 300-fold diluted solution of formulation oil prior to transplanting in the field（dipping treatment）. The efficacy of this dipping treatment against T. urticae was evaluated by laboratory tests and field tests. In laboratory tests using kidney beans , the corrected mortalities of adult females, nymphs, and eggs by the dipping treatment were 100%, 100%, and 93.7%, respectively. In the field tests conducted in 2017 and 2018, the population densities of T. urticae decreased by the dipping treatment in formulation oil. Further, compared to a chemosynthetic insecticide treatment, population densities of T. urticae were significantly suppressed for a prolonged period by additionally releasing the phytoseiid and spraying formulation oil on strawberry plants after the dipping treatment. This combination treatment had no effect on the growth and terminal flower bud emergence rate of strawberry. Thus, our findings suggest that this treatment effectively controls T. urticae.