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

ABSTRACT

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 LC50, 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 (rm), net reproductive rate (Ro), 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.