Residual contact vial (RCV) method was used to monitor insecticide resistance in field populations of the melon thrips, Thrips palmi. Median lethal doses (LD50) at 8 h post-treatment of six insecticides (chlorfenapyr, cyantraniliprole, cypermethrin, dinotefuran, emamectin benzoate and spinosad), which are commonly used for T. palmi control, were determined at 8 h post-treatment using a susceptible RDA strain. The diagnostic doses for on-site resistance monitoring of the six insecticides, which were determined as two-fold higher doses of LD90 for the RDA strain, were in the range of 0.299 to 164,25 μg-1cm2. To test the applicability of RCV for T. palmi, insecticide resistance levels in three field populations (Gyeonggi; GG_AS, Chungbuk; CB_CJ, Jeonbuk; JB_KJ) were evaluated. Field populations showed reduced mortality (0-50% mortality) to spinosad, cypermethrin, cyantraniliprole and emamectin benzoate, that they have different degree of resistances to these insecticides. In particular, all test field populations exhibited 0% mortality to spinosad, suggesting wide spread of spinosad resistance in the field. Moreover, no detectable mortality to emamectin benzoate was observed in JB_KJ strain, suggesting uneven distribution of emamectin benzoate resistant population of T. palmi. To provide more precise information on resistance profiles and distribution in T. palmi populations, it would be necessary to conduct a large scale resistance mapping for broad geographical regions.

• Min Ju Kim(Department of Agricultural Biotechnology, Seoul National University)
• Kyungmun Kim(Department of Agricultural Biotechnology, Seoul National University)
• Deok Ho Kwon(Research Institute for Agriculture and Life Sciences, Seoul National University)
• Si Hyeock Lee(Department of Agricultural Biotechnology, Seoul National University, Research Institute for Agriculture and Life Sciences, Seoul National University)