The Effect of Different Thiamethoxam Concentrations on Riptortus pedestris Development and Fecundity

The stink bug, Riptortus pedestris (Fabricius) (Hemiptera: Alydidae), is a highly destructive pest that significantly damages legume crops in East and South Asia. Neonicotinoid insecticides containing thiamethoxam are widely used to control R. pedestris in soybean fields. However, the current knowledge on the impact of different thiamethoxam concentrations on R. pedestris growth and reproduction is lacking and insufficient. The present study investigated the effects of thiamethoxam on the biological traits of R. pedestris after treatment with LC₁₀ (19.8 mg/L), LC₂₀ (31.6 mg/L), LC₃₀ (44.2 mg/L), LC₄₀ (58.9 mg/L), and LC₅₀ (77.0 mg/L) concentrations. These five thiamethoxam concentrations (LC₁₀~LC₅₀) reduced adult longevity and fecundity in the F₁ generation females. Thiamethoxam treatment also significantly decreased the population trend index, intrinsic rate of increase, net reproductive rate, gross reproductive rate, and finite rate of increase and increased the mean generation time. These results show that thiamethoxam hinders and suppresses the development and growth of the F₁ population of R. pedestris. Thiamethoxam is recommended for spray control during peak adult emergence, as it not only has a controlling effect on the parental generation but also a negative impact on the F₁ generations.