Abstract
The seasonal prevalence of Tetranychus kanzawai and synthetic pyrethroid (SP)-resistant Amblyseius womersleyi in tea fields under SP application was studied during the second tea season in 1994. The density of T. kanzawai peaked in mid-June and then declined. In response to this population change, the occurrence of A. womersleyi was also confirmed. Resistant A. womersleyi effectively suppressed mite damage to new leaves. In 34 plots of 40 assessed in the tested field, damage to new leaves in late June was lower than EIL (20%). Sucking pests Sirtothirips dorsalis and Empoasca onukii were suppressed better by SP than organophosphate insecticides. Simultaneous pest control by this pesticide resistant A. womersleyi and chemicals was also confirmed. A significant positive correlation was also detected between damage to new leaves at plucking and infestation of T. kanzawai when new buds sprouted. These results suggest that acaricide application harmless to A. womersleyi and the release of A. womersleyi or its integration effectively prevented damage on new tea leaves by T. kanzawai.
