Genes in CYP9 Asubfamily of P450 are associated with the resistance of insects to pyrethroids.In order to verify the induction effect of deltamethrin to CYP9 Ain Mamestra brassicae,RT-PCR and RACE were used to clone the full-length cDNA sequence of CYP9 Agene.Its mRNA expression profiles in different tissues at fifth-instar larvae and the effect of deltamethrin were detected by real-time PCR.The results would give us a basis for resolving the management problem of the resistance of M.brassicae to deltamethr...