Effects of bistrifluron resistance on the biological traits of Spodoptera litura (Fab.) (Noctuidae: Lepidoptera).

Spodoptera litura is one of the major insect pests of vegetables in Sichuan, China, and it has developed serious resistance to many traditional chemical insecticides. In this present study, S. litura individuals collected from five regions in Sichuan in 2017, which were detected the resistance to bistrifluron. We found that the resistance ratios (RRs) bistrifluron were in the ranges of 15.9- to 77.7-fold, respectively, compared with a laboratory susceptible (Lab-HN) strain. To elucidate the effect of bistrifluron on the life history parameters of S. litura, we established the bistrifluron-susceptible (Bis-UNSEL) and bistrifluron-resistant (Bis-SEL) strains based on the DY field population with the highest RR of 77.7-fold among the all field populations to bistrifluron compared with a laboratory Lab-HN strain. The results show that the Bis-SEL strain developed a 113.8-fold RR while that of the Bis-UNSEL strain was almost equal to that of the Lab-HN strain (with overlapping confidence intervals (CI) of their LC50 values, P < 0.05). Meanwhile, the life span of the egg and pupa stage of the Bis-UNSEL strain was prolonged, and the strain also showed shorter adult duration and lower fecundity. Demographic characteristics, such as the intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R0) in the Bis-SEL strain were significantly higher than the Bis-UNSEL strain, whereas the mean generation time (T) and gross reproduction rate (GRR) were lower. The results clearly showed that the developing resistance of bistriflueon on S. litura promoted its population growth. Therefore, the present study could provide useful informations for determining potential management methods to prevent the development of bistrifluron resistance in S. litura.