Abstract
I investigated the effects of spring skiffing on the densities of Tetranychus kanzawai in hedge or plucking surface of a tea field during early spring in 2005. The stages of T. kanzawai were almost adult females and eggs from 4 days before skiffing to 10 days after skiffing. The number of adult females in hedge increased rapidly from 3 days after skiffing to 10 days. The proportion of number of adult females before skiffing to 10 days after skiffing in plucking surface was 1.6, on the other hand, the proportion in hedge was 5.8. These results indicates that T. kanzawai adult females moved from branches and leaves which fell into the ground by skiffing to hedges of tea bush. I also investigated the effects of skiffing and the timing of acaricide application on the densities of T. kanzawai in hedge or plucking surface. Tea fields were subjected to one of three different treatments: acaricide spray before skiffing (plot A), acaricide spray after skiffing (plot B), or no acaricide (plot C). The densities of T. kanzawai adult female in hedge of plot A were significantly lower than those in plot B and C at 10 and 24 days after skiffing. The densities of T. kanzawai immature of plot A were significantly lower than those in plot B and C at 31 days after skiffing for the hedge and at 24 and 31 days after skiffing for the plucking surface. The rate of prevention for T. kanzawai in plot A was more than 80%, it was higher than that in plot B at 24 and 31 days after skiffing for the hedge and for the plucking surface. These results suggest that the application of acaricide before skiffing was more effective for controlling T. kanzawai than the application after skiffing.
