Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 7, 1996
Publication Date: N/A
Interpretive Summary: Prior work had demonstrated that younger stages of the German cockroach were more tolerant to various insecticides than adults. Pest control operators had also communicated to us that after insecticide applications, young German cockroaches seemed to survive the treatments better than adults (i.e. they were unable to kill younger stages). This phenomenon prevents effective control of German cockroaches. We identified the biochemical mechanisms responsible for this stage-dependent insecticide tolerance. Specifically, we showed that younger German cockroaches metabolize insecticide faster than adults. In addition, younger German cockroaches possess more detoxification enzymes than adults. We were able to make younger German cockroaches as susceptible as adults to insecticides with the addition of an insecticide synergist such as piperonyl butoxide. Therefore, these recommendations reduce insecticide load in the urban environment by making them more effective and prevents unnecessary insecticide applications.
Technical Abstract: Final instar nymphs and adult males of the Village Green strain of German cockroach were investigated to determine the biochemical mechanisms responsible for conferring stage-dependent propoxur tolerance. Propoxur susceptibility was dependent upon age of the final instar. Nymphs (1-day-old) were as susceptible to topically applied propoxur as adult males (7-days-old) while 7- and 12-day-old nymphs were up to 16-fold more tolerant. In vitro microsomal oxidation of propoxur was significantly higher (2.7-fold, based on per mg protein) in male and female final instars than in adult males. No qualitative differences in metabolite formation was observed between nymphs and adult males. Nymphs had higher cytochrome P450 content and methoxyresorufin O-demethylase and ethoxyresorufin O-deethylase constant values for propoxur in nymphs and adult males indicated that acetylcholinesterase insensitivity did not contribute to the enhanced nymphal tolerance. Propoxur recovered from cuticular rinses of adults and nymphs indicated that decreased insecticide penetration did not contribute to the enhanced nymphal tolerance.