Susceptibility levels of field populations of Frankliniella occidentalis (Thysanoptera: Thripidae) to seven insecticides in China

The western flower thrips, Frankliniella occidentalis (Pergande), is a widespread and serious agricultural pest. Controlling F. occidentalis is difficult because it rapidly develops resistance to many insecticides. To assess the development status (2016–2018) of insecticide resistance of F. occidentalis and to improve resistance management, we determined the susceptibility levels of field populations in China to seven commonly used insecticides (spinosad, spinetoram, abamectin, emamectin-benzoate, chlorfenapyr, thiamethoxam and β-cypermethrin). The results showed that F. occidentalis developed resistance to spinosad, spinetoram, abamectin, emamectin-benzoate, thiamethoxam and β-cypermethrin, and except for spinetoram and thiamethoxam, the resistance of southern populations to the other four insecticides was higher than that of northern populations. A population from Changping, Beijing, had the highest resistance level and its spinetoram resistance ratio was 16,972 (susceptible reference strain LC50 = 0.001 mg/L). Susceptibility to spinosad and abamectin varied greatly among the populations (LC50 values ranged from 0.006 mg/L to 9.943 mg/L for spinosad and from 1.071 mg/L to 939.410 mg/L for abamectin). The use of non-chemical control methods and IPM should be considered for the sustainable management of F. occidentalis populations.