Documenting resistance to modern insecticides and insect growth regulators in Helicoverpa armigera (Lepidoptera: Noctuidae) field populations from Karnataka, India

This study in Karnataka, investigated insecticide resistance in Helicoverpa armigera and related farmer practices. The toxicity of IGR (novaluron) and newer insecticides (indoxacarb, rynaxypyr, spinosad, flubendiamide and emamectin benzoate) was assessed on field strains and farmers were surveyed regarding pesticide use and resistance management. Results revealed varying resistance levels, with the RCR strain showing higher resistance to newer insecticides and novaluron. A positive correlation was observed among tested insecticides, notably between indoxacarb and rynaxypyr. Morphometric analysis suggested that larger larval and pupal dimensions in some strains were linked to higher resistance. Farmer surveys indicated low awareness of recommended agrochemicals and widespread use of higher than recommended pesticide doses (81.78%). Farmers primarily relied on agrochemical vendors for advice (85.78%), rather than agricultural experts. Compliance with resistance management strategies like avoiding similar chemicals or using traps and refugia was very low. Conventional insecticides remained dominant (54.22%) in use. This study provides baseline data for newer insecticides and highlights early resistance development. It underscores the urgent need for enhanced farmer education and integrated pest management strategies, including judicious use of diverse mode of action insecticides like spinosad and IGRs, to combat escalating resistance in H armigera.