Estimation of Toxicity of Spinosad Using Two Different Bioassay Methods Against Cotton Bollworm, Helicoverpa armigera (Hub.)

Two different bioassay methods; larval dip bioassay and surface diet bioassay were tested for the contact/ingestion toxicity and to see the advantage of one method over the other using spinosad against second instar Helicoverpa armigera. Little difference was observed in LC50 values which were 170 and 130ppm for both the methods, however ingestion/contact toxicity (surface diet bioassay) as compared to contact toxicity only (larval dip bioassay) remained comparatively but not significantly different. Results also proved that surface diet bioassay had advantage over larval dip bioassay as it provided better estimate of potential toxicity.