Comparative demography of Tetranychus urticae on cotton varieties using the age-stage, two-sex life table approach

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a major constraint to cotton production worldwide. The age-stage, two-sex life table approach provides a comprehensive assessment of arthropod population dynamics by incorporating stage differentiation, variable developmental rates, and the contribution of both sexes to population growth. This method provides more accurate estimates of demographic parameters and host suitability than conventional female-based life tables. Yet comparative demographic responses of T. urticae to cotton varieties remain insufficiently characterized in Bangladesh. Therefore, this study evaluated the life-history traits and population dynamics of T. urticae on five cotton varieties (CB-12, CB-14, CB-15, HC-1, and M-1) using the age-stage, two-sex life table approach under controlled laboratory conditions. The host plant significantly influenced development, reproduction, and demographic parameters. Development from egg to adult ranged from 14.92 days on M-1 to 16.34 days on CB-14. Fecundity was highest on CB-15 (72.38 eggs female^-1) and CB-14 (71.16 eggs female^-1), and lowest on CB-12 (42.31 eggs female^-1) and HC-1 (43.13 eggs female^-1), indicating substantial variation in host suitability. The intrinsic rate of increase (rₘ) and finite rate of increase (λ) of T. urticae were greatest on M-1 (0.1694 and 1.1846 day⁻¹, respectively), followed by CB-15 (0.1557 and 1.1685 day^-1), reflecting faster population growth on these varieties. In contrast, CB-12 and HC-1 consistently exhibited reduced fecundity and lower population growth potential (r_m = 0.1487 and 0.1474 day^-1, respectively). The net reproductive rate (R₀) of T. urticae showed similar trends, being highest on CB-15 (49.98 offspring female^-1) and the lowest on HC-1 (27.85 offspring female^-1). M-1 and CB-15 were the most susceptible hosts for T. urticae, whereas CB-12 and HC-1 exhibited greater levels of resistance. These findings identify CB-12 and HC-1 as promising sources of host plant resistance and demonstrate the importance of varietal selection for sustainable management of T. urticae in cotton production systems.