Laboratory Evaluation of Toxicity of Insecticide Formulations from Different Classes against American Cockroach (Dictyoptera: Blattidae)

BACKGROUND: The present study was designed to investigate the insecticidal efficacy of four different classes of insecticides: pyrethroids, organophosphates, phenyl-pyrazoles and neo-nicotenoids. One representative chemical from each class was selected to compare the toxicity: deltamethrin from pyrethroids, Dichlorovinyl Dimethyl Phosphate (DDVP) from organophosphates, fipronil from phenyl-pyrazoles and imidacloprid from neo-nicotenoids. The objective of this study was to determine which of these insecticides were most effective against American cockroach. METHODS: These insecticides were tested for their LC(50) values against Periplaneta americana under topical bioassay method, using different concentrations for each chemical. RESULTS: Fipronil 2.5% EC was highly effective at all concentrations applied, while DDVP 50% EC was least toxic amongst all. One way analysis of variance confirmed significant differences between mortality of P. americana and different concentrations applied (P< 0.05). CONCLUSION: Locality differentiation is an important factor in determining the range of resistance between various localities, as all three localities behaved differently in terms of their levels of resistance.