The relative toxicity of emulsions of various pyrethroids was evaluated against the third instar larvae of Pieris brassicae in the laboratory. Except fenvalerate, the synthetic pyrethroids viz, deltamethrin, γ-cyhalothrin, alphamethrin, bifenthrin, fenpropathrin and β-cyfluthrin were found to be highly toxic, their relative toxicity values being 23.2, 14.5, 10.5, 8.92, 7.73 and 6.12 times more compared to cypermethrin. Regardless of the method of application, relative efficacy of various synthetic pyrethroids was the same. A comparison of the relative resistance based on LC50 values of Pieris brassicae, Spilarctia obliqua and Spodoptera litura to various synthetic pyrethroids indicated higher susceptibility to P. brassicae amongst these three pests. The base line data thus generated would provide a record for detecting the resistance level of P. brassicae to vvriouu synthetic pyrethroids.
Pieris brassicae, systhetie pyrethroids
