Induction of cytochrome P450 monooxygenase activity in the two-spotted spider mite Tetranychus urticae and its influence on acaricide toxicity

Detoxification by cytochrome P450 monooxygenases is an important mechanism involved in pesticide resistance in insects and mites. The activity of these enzymes can be induced by a variety of chemicals. The aim of this study was to evaluate the effect of six P450 inducers (phenobarbital, barbital, 3-methylcholanthrene, geraniol, isosafrole, pentamethylbenzene), known to have an inducing activity in insects and mammals, on the O-deethylation activity in the two-spotted spider mite Tetranychus urticae. Treatment with barbital, phenobarbital and geraniol resulted in a dose-dependent increase in activity. Neither 3-methylcholanthrene, isosafrole nor pentamethylbenzene were effective inducers. Time course studies showed that induction by geraniol and barbital started rapidly within a period of 1-4 h after initiation of the treatment, while maximal activity was reached within 4 and 48 h, respectively. In addition, it was shown that induction with xenobiotic compounds can alter the monooxygenase-mediated acaricide tolerance in a susceptible strain of T. urticae. Although barbital induced higher levels of P450 activity, geraniol proved to be a better compound to decrease toxicity of the tested acaricides.