2020 Volume 2020 Issue 71 Pages 149-156
Bioassays were conducted to assess the efficacy of 11 acaricides against 12 populations of two-spotted spider mite, Tetranychus urticae, collected from apple orchards in the central and southern Miyagi prefecture. Milbemectin, BPPS, acequinocyl and bifenazate, which were used infrequently in the last 10 years, showed high efficiency in all or most populations. The efficiency of cyenopyrafen and cyflumetofen, which were frequently used in most orchards are classified as IRAC code 25A, was reduced in multiple populations. Spiromesifen, which was also frequently used, showed high efficiency in most populations but reduced efficiency in some populations. This indicated that some precautionary measures, such as biennial application, need to be taken to delay the reduction of acaricides susceptibility. Surveys of the surrounding environment indicated that the orchards where many acaricides showed a higher efficiency tend to be surrounded by forest.
