Implications of cypermethrin exposure on population dynamics and fitness traits of laboratory-selected resistant and susceptible populations of Spodoptera litura (Fabricius).

The tobacco cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) is an economically important agricultural polyphagous pest worldwide. It has shown high resistance to several insecticides, including cypermethrin, a synthetic pyrethroid that is used in large-scale commercial agricultural applications. The present study investigated the development of selection-induced resistance to cypermethrin and associated fitness costs in S. litura. After continuous exposure to cypermethrin for consecutive fifteen generations, the cypermethrin-selected population (CYP-Sel) of S. litura developed a 21.2-fold resistance. The CYP-Sel strain had a relative fitness of 0.16 when treated with LC, prolonged larval duration, and development time. Meanwhile, the strain also showed shorter adult duration, lower fecundity, and hatchability compared with the Unsel-Lab population. CYP-Sel population showed a significant disadvantage in intrinsic rate of natural increase (r), net reproductive rate (R), and finite rate of increase (λ) when compared to the Unsel-Lab population. This knowledge could help to design resistance management strategies against this particular pest, along with potential management strategies to overcome the development of resistance.