We examined the effect of insecticides on an important pest, Thrips palmi Karny, collected in Shizuoka Prefecture from three melon greenhouses in 2013 and ten melon greenhouses in 2015. Female adults were examined using a kidney bean leaf dipping method under laboratory conditions. The mortalities of T. palmi populations examined in 2013 were high with emamectin benzoate and pyridalyl on all populations, and were high with spinosad and spinetoram except for one population. However, mortality levels were low with cypermethrin, four neonicotinoid insecticides and abamectin on all populations. The mortalities examined in 2015 were at high levels with nitenpyram on two of ten populations, whereas at low levels with dinotefuran, spinosad, spinetoram, emamectin benzoate and pyridalyl, with a few exceptions.