Relative resistance of Bihar hairy caterpillars to insecticide mixtures

The relative toxicity of emulsions of various insecticide mixtures was evaluated against Bihar hairy caterpillar, Spilarctia obliqua in laboratory by two different techniques viz., direct spray and leaf residue method. On the basis of LC₅₀ values, Virat, Bulldockstar, Anaconda. Polytrin C, Ducord, Nurelle D, Sparak, Nagata and Spectrum were 5. 36, 5. 88, 5. 04, 3. 40, 3.23, 2.74, 1.68, 1.62 and 1.13 times more toxic than Super D. Koranda was 0.87 times less toxic than Super D when evaluated by direct spray method. Leaf residue method showed 6.45, 2.70, 2.42, 2.41, 1.75, 1.41, 1.38, 1.29, 1.21 and 1.17 times respectively more toxicity than the direct spray method in case of bulldockstar, Anaconda, Spark, Spectrum, Nagata, Polytrin C, Super D, Virat, Koranda and Anakonda. A comparision of the relative resistance based on LC₅₀ values of S. obliqua, Spodoptera litura and Helicoverpa armigera to various insecticide mixtures indicated that H. armigera was relatively resistant amongst these three pests.