LAUSR

Abstract The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is a well-known pest mite with an extensive host range worldwide. The control of T. urticae populations mostly relies on the application of synthetic acaricides or pesticides. Chlorfenapyr is a broad spectrum insecticide/miticide effective against agriculturally important pests. In this study, sublethal effects (LC10, LC20 and LC30) of this insecticide on demographic parameters of T. urticae based on the age-stage, two-sex life table theory were investigated under laboratory conditions [25 ± 2 °C, 60 ± 5 % RH and 16:8 (L:D) h]. According to the obtained results, the LC50 value for females of T. urticae was 47.66 ppm. The egg incubation, protonymph, as well as deutonymph durations of both sexes were significantly reduced as a consequence of treatment with LC20 and LC30 of chlorfenapyr. In addition, our results indicated that oviposition period in LC10 lasted 9.62 days, which was closer to the control (9.73 days); while it significantly decreased with increasing the concentration from LC20 to LC30. Furthermore, LC20 and LC30 treatments decreased the fecundity of females by 55.5% and 61.6%, respectively. The values of both intrinsic (r) and finite rates of increase (λ) at LC20 and LC30 was significantly inferior to other experimental treatments. It could be concluded that along with the lethal doses, the sublethal concentrations of chlorfenapyr profoundly reduced the population growth rate of T. urticae.