title: Pharmacodynamics of malathion and carbaryl in susceptible and multiresistant German cockroaches (Dictyoptera: Blattellidae).
abstract: Studies with malathion and carbaryl were done to compare toxicity; absorption, metabolism, internal accumulation, and excretion; and in vivo inhibition of acetylcholinesterase (AChE) after topical applications to adult male susceptible (S, Orlando normal) or multiresistant (R, HRDC) German cockroaches, Blattella germanica (L.). Compared with the S strain, R cockroaches were highly resistant to malathion (about 33-fold) and only moderately resistant or tolerant to carbaryl (about 5-fold). Tests with topically applied 14C-labeled malathion and carbaryl indicated that both compounds penetrated rapidly and radioactive products were readily excreted. Rates of absorption or excretion in S and R strains did not differ significantly. Both insecticides were extensively metabolized; each yielded the same array and similar concentrations of metabolites in insects from either strain. In contrast, metabolic detoxification of malathion and carbaryl was significantly greater in R cockroaches when the insects were treated by injection. Strains did not differ significantly in the in vitro inhibition of brain AChE by either malaoxon or carbaryl. However, dramatic differences were observed between strains in the in vivo inhibition of AChE during a 6-h test period after topical treatment with malathion, and moderate but significant differences occurred between strains in the in vivo inhibition of AChE by carbaryl. These data suggest that the strong resistance to malathion and moderate resistance or tolerance to carbaryl in R cockroaches is probably a result of enhanced capability for metabolic detoxification.
authors.forename: D L
authors.initials: DL
authors.lastname: Bull
authors.forename: R W
authors.initials: RW
authors.lastname: Wadleigh
authors.forename: R S
authors.initials: RS
authors.lastname: Patterson
mesh_terms: D000818:Animals; D012721:Carbaryl; D003058:Cockroaches; D007305:Insecticide Resistance; D008294:Malathion; D008297:Male
chemical_list: D012721:Carbaryl; D008294:Malathion