Sub-Lethal Effects of Emamectin Benzoate on Life History Traits and Relative Fitness of the Tobacco Caterpillar, Spodoptera litura (Lepidoptera: Noctuidae)

Abstract

This experiment was carried out in the laboratory of Department of Entomology, College of Agriculture, Rajendranagar during kharif, 2022. The sublethal effects of emamectin benzoate (EB) were investigated on Spodoptera litura in field collected population from vegetable crops of Chevella and Maheshwaram mandals, Rangareddy district, Hyderabad under laboratory conditions. Emamectin benzoate (EB) is widely used in the control of lepidopteran pests, but there is sparse information available regarding its sublethal effects on S. litura. The LC50 value was 0.018310 and 0.018078 per cent in Chevella and Maheshwaram populations, respectively for 24 hr exposure time. LC25 of the insecticide was used for sublethal effect study in both field populations. The sub-lethal concentrations of the emamectin benzoate resulted in reduced weight gain of all the stages of S. litura, prolonge larvae, pupae and adult duration, increased larval mortality and decreased female survival, reduced pupation, emergence and hatchability rates, as well as fecundity. Further studies on demographic parameters to determine the population dynamics of resistance acquired populations of S. litura revealed an increase in mean generation time (T) and a decrease in net reproductive rate (Ro), intrinsic rate of increase (rm), finite rate of natural increase (λ) and reduced relative fitness (Rf) with 0.67 and 0.68 in Chevella and Maheshwaram populations, respectively.