Date Received: 19-11-2025 / Date Accepted: 23-01-2026 / Date Published: 28-02-2026
The beet armyworm Spodoptera exigua (Hübner) is a major pest of Welsh onion in many regions of Vietnam. In this study, we assessed the effects of insecticides on the biological and developmental parameters of S. exigua using sublethal concentrations (LC₃₀) of formulations containing chlorantraniliprole (Prevathon 5SC) and spinosad (Asaka 25SC). The experiment was conducted using the leaf-dip method on 2nd instar larvae combined with an individual-based age-stage, two-sex life table study of S. exigua. Results indicated that the exposure to LC₃₀ concentrations of chlorantraniliprole and spinosad significantly reduced pre-adult survival, prolonged developmental duration, and decreased adult female longevity and fecundity in comparison with the control. The beet armyworm exposed to LC₃₀ of chlorantraniliprole and spinosad showed markedly reduced population growth parameters, including the net reproductive rate (R₀: 90.87 and 64.55), the intrinsic rate of increase (rₘ: 0.1504 and 0.1332), and finite rate of increase (: 1.162 and 1.142), compared with the control (R₀ = 180.03; rm = 0.181; = 1.198). In contrast, the mean generation time T (29.99 and 31.29 days, respectively) was prolonged in relation to the control (28.7 days). Compared with chlorantraniliprole, spinosad caused a more pronounced reduction in fecundity and population growth potential; therefore, it can be recommended for managing this pest. These findings provide valuable information for optimizing the use of insecticides within integrated pest management (IPM) programs targeting S. exigua on Welsh onion.
