The immersion of American cockroaches resulted in the highest knockdown (100%) and mortality (84.00 [+ or -] 4.00%).
When compared with the concentration needed to achieve [LC.sub.50] for German cockroaches ([LC.sub.50] = 0.56%), it took a significantly lower concentration of dishwashing liquid to achieve [LC.sub.50] for American cockroaches using the immersion application ([LC.sub.50] = 0.24%) (Table 4).
Means separation by SNK indicated that American cockroaches that were sprayed had significantly less knockdown (56.8%) and mortality (75.2%) compared with all other combinations of cockroach species and application methods (99-100%) (Table 5).
(1984) reported that a splash of commercially available soaps in water would kill American cockroaches at a 1-2% solution.
The [LC.sub.50] for American cockroaches exposed by immersion was 0.24%, but not significantly less than the [LC.sub.50] (0.56%) for the German cockroaches.