<p>Subletahal effects of fenpropathrin on the oxalis spider mite, <em>Tetranychina hatri </em>(Ewing) (Acari: Tetranychidae)</p>

The sublethal effects of fenpropathrin on the oxalis spider mite, Tetranychina harti (Tetranychidae) were investigated. The results showed that, relative to the control group, sublethal doses of fenpropathrin significantly shortened the developmental duration of immature offspring in the LC15 group (P < 0.05) but significantly prolonged it in the LC30 group (P < 0.05). Furthermore, these sublethal exposures shortened the pre-oviposition period while prolonging the oviposition period of F1 female adult mites. Notably, a significant reduction in mean fecundity per female was observed only in the LC15 group compared to the control (P < 0.05). The cumulative survival rate curves and age-specific fecundity curves indicated that sublethal concentrations (LC15 and LC30) of fenpropathrin did not exert a clearly adverse effect on the survival or fecundity of Tetranychina harti. Both treatment groups exhibited higher net reproductive rates (R0) than the control. Similarly, the intrinsic rates of increase (rₘ) in the LC15 and LC30 groups exceeded that of the control, and the finite rates of increase (λ) in both treatment groups were also higher. In addition, the population doubling time (DT) was shorter in the treatment groups than in the control. These findings suggest that sublethal exposure to fenpropathrin may compromise its efficacy in controlling this mite population.