Excito-repellency and fumigation potentials of chlorpyrifos and cypermethrin against the American cockroach, Periplanta americana (L) (Dictyoptera: Blattodea)

Abstract

The repellence and fumigation properties of two insecticidal agents, chlorpyrifos and cypermethrin, were tested against the American cockroach, Periplaneta americana, in laboratory assays. The insecticides were diluted in ace tone and tested against the roaches in predetermined concentrations and in an untreated control. The experimental cages were choice chambers and a non-choice chamber for repellency and fumigation assays, respectively. Both tested insecticides repelled cockroaches in a dose-dependent manner. Chlorpyrifos induced a significantly higher P<0.05 repellence under concentrations 5.0 and 10.0 mg/ml in both sexes of cockroaches. The repellency indexes range between 0.22-0.63 and 0.11-0.66 for male and female, respectively. Chlorpyrifos had moderate repellence indexes (0.50-0.66) while cypermethrin showed lower repellency indexes (0.11-0.36). Cypermethrin induced faster knockdown of KT50 and KT100 in both sexes of cockroach in the fumigation assay. However, chlorpyrifos produced faster mortality MT50 and MT100 in both sexes. It was concluded that both insecticides were effective in the control of P. americana. However, while chlorpyrifos could double as a repellent and a fumigant, cypermethrin was only effec tive as a fumigant. Therefore, the modes of application of these insecticides relatively dictate the levels of control they exhibit against this insect pest.