2010 Volume 54 Issue 4 Pages 205-207
The white peach scale, Pseudaulacaspis pentagona (Targioni), is one of the most important pests infesting tea trees in Japan. We investigated the susceptibility of populations of the insect collected from tea fields in Shizuoka and Miyazaki prefectures against five insecticides, methidathion, isoxathion, buprofezin, fenpyroximate alone and a fenpyroximate- buprofezin mixture. The susceptibility was evaluated by spraying the pesticides on first instar larvae on tea branches. The corrected mortality of Shizuoka populations after treatment with 200 ppm buprofezin was less than 21.7%, indicating a high resistance to buprofezin. The LC50 of methidathion varied from 26.8 ppm (Miyazaki population) to 773.0 ppm (Yui population in Shizuoka), and thus resistance to methidathion was also suggested; however, Shizuoka populations were susceptible to both fenpyroximate treatments, as were the Miyazaki populations.