American cockroach (Periplaneta americana) is a tropical species that can be found in Indonesia and elsewhere. It is of public health importance as it is a vector of some human pathogens. Soap, including bar soap can be used as pesticide for cockroaches. It contains surfactant as an active ingredient. However, the effectiveness of low-cost and commercially available bar soap in controlling these cockroaches has received little attention and is not fully understood. This paper reports the effect

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... of bar soap solution exposure on the American cockroach and determination of the LC 50 of solution. The research used True-Experimental design with a Post-Only Control Group. Cockroaches were randomly selected from the rearing cage and the post-test measured cockroach mortality after exposures. The soap solutions were prepared in 4 concentrations (10%, 20%, 30% and 40%), then sprayed directly onto 15 cockroaches with 5 replications. The cockroach condition was observed at 24 hr after treatment and the number of cockroach deaths were counted. Normality data were tested using the Shapiro-Wilk test (P=0.05) and analysed using Friedman's test to determine the difference of variance of concentration. Abbott's test was used to specify the effectiveness of soap solution and the LOGIT test was used to determine LC 50. The results suggest that cockroach death occurred after exposure and there was a significant difference between the effectiveness of the soap solution concentrations on mortality (p=0.000). The Logit analysis indicated that the LC 50 of bar soap solution was at 32%. It can be concluded that the soap solution has a killing effect on the American cockroach with LC 50 at 32% after 24 hr of treatment.