Resistance to Lambda-Cyhalothrin and Deltamethrin with Associated Fitness Costs in a Tomato-Derived Population of Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract

A field population of Helicoverpa armigera collected from tomato at Pirsabak was compared with a susceptible laboratory strain to characterise pyrethroid resistance, cross-resistance, and associated life-history costs. Leaf-dip bioassays produced resistance ratios of 142.6 for lambda-cyhalothrin and 89.4 for deltamethrin, whereas the chlorantraniliprole ratio was 1.8. The resistant population developed more slowly, had lower survival and pupal weight, and produced fewer viable eggs. Fecundity declined by 26.5%, and egg viability declined by 21.4 percentage points, equivalent to a 22.6% relative reduction. The results support suspension of routine pyrethroid use where resistance is confirmed and rotation across effective modes of action. The concentration–mortality curves are reconstructed from supplied LC50 and slope parameters and are illustrative; raw dose-level mortality records are required for publication-grade verification.