Sublethal and Transgenerational Effects of Isocycloseram on the Life Table of Two-Spotted Spider Mites (Tetranychus...

Tetranychus urticae is a highly destructive, polyphagous mite that has developed resistance to multiple acaricides, necessitating the evaluation of new compounds. Isocycloseram is a novel insecticide with potential to control this mite; the effects of its sublethal concentrations are still uninvestigated. In this study, an age-stage, two-sex life table model was used to evaluate the sublethal effects of isocycloseram concentrations (LC₁₀ and LC₃₀) on population growth, reproduction, and development of the two-spotted spider mite. The results showed that the LC₁₀ and LC₃₀ values were 0.012 mg/L and 0.022 mg/L, respectively. Sublethal concentrations of LC₁₀ significantly affected population growth by reducing fertility, while LC₃₀ significantly prolonged the immature stage and reduced average fecundity by 37%. With the LC₃₀ treatment, the net reproductive rate R₀ decreased by 43%, and the intrinsic rate of increase r decreased significantly, from 0.152 day^-1 to 0.117 day^-1. The doubling time DT was extended by 30%, from 4.55 days to 5.92 days. This study covers the importance of life table analysis for investigating sublethal effects and for ensuring that, when isocycloseram is incorporated into integrated pest management, both its direct toxicity and its effects on population dynamics are considered.