Host induced variability in the tosicity of insecticides against spodoptera litura and Helicoverpa armigera

An experiment was undertaken at the Department of Agricultural Entomology, University of Agricultural Science, Dharwad. It involved bioassay of indoxacarb, flubendiamide, chlorpyrifos and Bacillus thuringiensis subsp.kurstaki (Btk) against Spodoptera litura (Fab) and Helicovepa armigera (Hubner) populations collected from different host crops. S. litura was collected from cabbage, soybean and groundnut while H. armigera from tomato, chickpea and cotton. S. litura collected from groundnut was highly susceptible with lower LC₅₀ values against the insecticides viz., indoxacarb (15.91 ppm), flubendiamide (11.69), chlorpyrifos (50.36) and B. thuringiensis subsp. kurstaki. S. litura collected from cabbage was found to be more resistant with higher LC₅₀ values against all of the insecticides. Similarly, H. armigera larvae collected from cotton was more susceptible with lower LC₅₀ values against indoxacarb, flubendiamide and chlorpyrifos, whereas the larvae collected from tomato showed resistance towards all of the insecticides.