Comparative study of the fitness of Tetranychus urticae on different apple cultivars and Timing of control using age-stage two-sex life table analysis.

Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most serious pest mites damaging crops. The life table and projection of the T. urticae population growth on two apple cultivars (Gala and Golden Delicious) were analysed using the age-stage two-sex life table procedure at 26 ± 1 °C, 70 ± 5% RH, and a photoperiod of L: D = 16:8 h. The stage-specific developmental duration and pre-adult survival of T. urticae were unrivalled between the two cultivars. Population parameters for T. urticae, including R0, r, and λ, exhibited higher values on the Gala cultivar compared to Golden Delicious, resulting in the greatest female fecundity recorded on Gala, with an average of 59.71 eggs per female, in contrast to the 39.01 eggs per female noted on Golden Delicious. The 0.025th and 0.975th percentile confidence intervals for T. urticae population parameters and survival rate were calculated utilizing the bootstrap resampling technique with 100000 resamples. The unrestricted growth of an initial cohort of 10 eggs over 60 days demonstrated that the T. urticae population could expand to 174 and 66 individuals on Gala and Golden Delicious, respectively. Under control conditions, the population did not exceed 20 individuals on either cultivar. This research indicated that T. urticae exhibited greater fitness on Gala than on Golden Delicious. It also highlighted that combining life table data with the age-stage structure of both sexes enables optimal timing of control. Additional life table-focused studies that involve temperature and host plants are necessary to refine the findings and conclusions.