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

Abstract

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 LC50 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.

Keywords: Efficacy; Insecticides; Periplaneta americana; Resistance; Topical bioassay.

Fig. 1

Regression line of (a) Imidacloprid 5% SC (b) Fipronil 2.5% EC (c) Deltamethrin 2.5% SC and (d) DDVP 50% EC on mean mortality of SMH (locality 1) of P. americana (L)

Fig. 2

Regression line of (a) Imidacloprid 5% SC (b) Fipronil 2.5% EC (c) Deltamethrin 2.5% SC and (d) DDVP 50% EC on mean mortality of KTCH (locality 2) of P. americana (L)

Fig. 3

Regression line of (a) Imidacloprid 5% SC (b) Fipronil 2.5% EC (c) Deltamethrin 2.5% SC and (d) DDVP 50% EC on mean mortality of KLPT (locality 3) of P. americana (L)