Abdou, D.A.M., M.M. Elbokl, A.E.M. Abd Elmageed and M.G. Habashy. 2023. Lethal and Sublethal Effects of Mixed Pesticides on Tetranychus urticae Koch and its Predator Phytoseiulus persimilis. Arab Journal of Plant Protection, 41(1): 40-47. https://doi.org/10.22268/AJPP-41.1.040047 Tetranychus urticae Koch is considered one of the most economically important pests on a wide range of crops in orchards worldwide. T. urticae control has been largely based on the utilization of acaricides. Sublethal effects of Romectin gold 32.8% SC (Abamectin 2.8% + Imidaclopride 30%) and AgriFlix 18.56% SC (Thiamethoxam 15.24% + Abamectin 3.23%) were studied on toxicity index and life-table parameters of T. urticae. LC25 concentration of Romectin gold and AgriFlix that were 0.0019 and 0.013 ppm, respectively, were utilized for sublethal studies. All acaricides showed a significant effect on T. urticae. Results obtained indicated that Romectin gold was the compound that had the higher effect on adult females of T. urticae and its predatory mite P. persimilis than AgriFlix. Sublethal concentrations of Romectin gold and AgriFlix may influence the durability of pre-adult stages, longevity, and biological parameters of T. urticae. The duration of life cycle of both females and males decreased significantly compared to the control with no significant effect between the two tested compounds. At the same time, Romectin gold produced the highest life cycle and life span. AgriFlix significantly decreased the pre-oviposition period with the lowest time of 1.10 days compared with 2.00 days for the control. To the contrary, Romectin gold had no significant effect on the preoviposition period. On the other hand, treatments with both Romectin gold and AgriFlix decreased significantly the oviposition period compared with the control. Romectin gold and AgriFlix significantly reduced the total number of eggs produced per female. AgriFlix acaricide decreased the total number and the daily rate of eggs produced by 73.36 and 65.05%, respectively. Results showed that exposure of females to sublethal concentrations of Romectin gold and AgriFlix reduced the net reproductive rate (R0), while intrinsic rate (rm) was increased compared to the control. Similarly, the finite rate of increase (exprm) for the control was significantly higher than that for Romectin gold and AgriFlix. Additionally, it was found that mean generation time (T) of the control was significantly shorter than that of Romectin gold and AgriFlix. Meanwhile, sex ratio was the same for control, Romectin gold and AgriFlix. Keywords: Sublethal effects, toxicity index, Life-table parameters, Abamectin, Imidaclopride and Thiamethoxam.