trasal-contact method test using glass petri-dish rather than the conventional glass jar was used to evaluate the permethrin toxicity and synergism effect of piperonal butoxode (pbo) on nymphae of five strains of blattella germanica (l.). the test was carried out on 2-3 days old of first nympal stage, at four replicates of 10 cockroaches. the susceptible strain showed t50 and kt50 of 12.81 and ...