Release strategies of Amblyseius womersleyi and population dynamics of Amblyseius womersleyi and Tetranychus urticae:: II.: Test of two release rates on apple

The two-spotted spider mite, Tetranyuchus urticae Koch is an important pest in Korean apple production. We tested two release rates of the predatory mite, Amblyseius womersleyi Schicha for biological control of T urticae in two varieties of apple, 'Fuji' and 'Tsugaru'. Mass-reared A. womersleyi were transferred to apple canopies in an experimental apple orchard plot in early season when T urticae densities were low. The effect of A. womersleyi release on T urticae peak density was significant in both apple varieties. Tetranychus urticae peak densities were the reverse order of the release rates of A. womersleyi. Cumulative mite-days per leaf were maintained below 200 throughout the season regardless of the initial A. womersleyi release rate or apple variety. Initial settlement and subsequent conservation of A. womersleyi are suggested as important factors for successful biological control of T urticae in apple orchards. Further research and implementation of the results are discussed relative to IPM.