Susceptibility of five thrips pests to spinetoram and the frequency of G275E target-site mutation in a major vegetable production region of China

The control of thrips pests primarily relies on the application of insecticides. However, the effective implementation of chemical control is complicated by varying levels of insecticide resistance among species and populations. In this study, we investigated the susceptibility of five thrips pest species on vegetables to a commonly used insecticide, spinetoram, and determined the frequency of the G275E target site mutation in a major vegetable production region in China. Among the 27 tested populations, Thrips palmi exhibited the lowest susceptibility, with LC₅₀ values ranging from 21.15 to 136.40 mg/L, and a mutation frequency of 52.08 %–93.75 %. Three populations of Frankliniella occidentalis had LC₅₀ values from 7.44 to 11.24 mg/L, while a fourth population was significantly more susceptible (1.75 mg/L). A G275E mutation frequency of 15.8 % was detected in one of the four F. occidentalis populations. In contrast, populations of Thrips tabaci, Megalurothrips usitatus, and Frankliniella intonsa had relatively low LC₅₀ values (0.39–1.44 mg/L, 0.41–7.98 mg/L, and 0.03–1.24 mg/L) and a mutation frequency of 0 %, indicating that these species remain largely susceptible to spinetoram. Our study demonstrates the varied susceptibility of thrips pests to spinetoram, highlighting the ongoing challenge of insecticide resistance.