Abstract: 【Aim】 The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is an important insect pest of rice. The present study aims to determine the sublethal effects of pymetrozine on the development and reproduction of this insect and its susceptibility to other insecticides. 【Methods】 The life table method was used to evaluate the sublethal effects of pymetrozine (LC₁₀ and LC₂₅) on developmental duration, survival rate, emergence rate and longevity of F₀ and F₁ generations of S. furcifera and rice stem dipping method was adopted to determine its susceptibility to other insecticides after pymetrozine (LC₁₀ and LC₂₅) treatment. 【Results】 The developmental duration of the F₀ generations of S. furcifera treated with sublethal concentrations (LC₁₀ and LC₂₅) of pymetrozine for 48 h was increased by 1.98 d and 4.25 d, the longevities were shortened by 0.49 d and 1.73 d, the survival rates (85.00% and 68.50%, respectively) of the 3rd-5th instar nymphs and the emergence rate (75.89% and 67.78%, respectively) decreased as compared with the control (92.00% and 85.90%, respectively), but significant difference was just observed in generation duration between the LC₂₅ treatment group and the control. Furthermore, the F₁ generation of S. furcifera exposed to sublethal concentrations (LC₁₀ and LC₂₅) of pymetrozine for 48 h had decreased emergence rate (76.97% and 68.94%, respectively), copulation rates (77.79% and 66.44%, respectively), egg hatching rates (73.19% and 68.67%, respectively), fecundity (112.36 and 88.34 eggs laid per female, respectively), and relative fitness (0.41 and 0.20, respectively) as compared with the control (88.22%, 86.67%, 87.26%, 147.80 eggs laid per female and 1.00, respectively). The susceptibility of pymetrozine-treated S. furcifera to thiamethoxam, chlorpyrifos, and buprofezin showed that the LC₅₀ values of the three chemicals were 2.16, 40.87 and 3.12 mg/L in LC₁₀ treatment group, and 4.93, 17.96 and 8.39 mg/L in LC₂₅ treatment group, respectively. The relative toxicity index (RTI) of thiamethoxam, chlorpyrifos and buprofezin to S. furcifera indicated that the susceptibility of pymetrozinetreated S. furcifera to these three insecticides was reduced. 【Conclusion】 Pymetrozine at sublethal concentrations can reduce the fecundity and population growth of S. furcifera and make it less susceptible to thiamethoxam, chlorpyrifos and buprofezin.

Key words: Sogatella furcifera; pymetrozine, sublethal effect, fitness, population trend index, insecticide susceptibility