Persian Journal of Acarology

Abstract 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.

Abstract The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a major agricultural pest, and the predatory mite Phytoseiulus persimilis Athias-Henriot is one of its most effective natural enemies. Since temperature strongly influences predator biology, in the present study, the effects of five constant temperatures (21, 23, 25, 27, and 29 °C) on the development, survival, and reproduction of P. persimilis using age-stage and two-sex life table analysis were evaluated. Developmental time decreased with increasing temperature, while reproductive onset occurred earlier at warmer conditions. Maximum fecundity, net reproductive rate (R0 = 14.62), and intrinsic rate of increase (r = 0.35) were recorded at 25–27 °C, indicating an optimal range for population growth. However, adult longevity and reproductive performance sharply declined at 29°C, suggesting heat stress limitations. These results confirmed that P. persimilis exhibits peak biological performance at moderate temperatures (24–27°C), reinforcing its suitability as a biocontrol agent under controlled environments but highlighting reduced efficiency under extreme heat. The findings provided practical insights for optimizing mass rearing and field release strategies within integrated pest management programs.