Transcriptional overexpression of CYP6B8/CYP6B28 and CYP6B9 is a mechanism associated with cypermethrin survivorship in field-collected Helicoverpa zea (Lepidoptera: Noctuidae) moths.

BACKGROUND

There are multiple reports of resistance to pyrethroid insecticides in Helicoverpa zea (Boddie); however, metabolic mechanisms responsible for insect survivorship have yet to be elucidated at the molecular level. Here, the transcriptional expression of two cytochrome P450 genes involved in pyrethroid metabolism, CYP6B8/CYP6B28 and CYP6B9, in H. zea male moths surviving discriminating dosages of cypermethrin in the adult vial test were investigated using quantitative PCR.

RESULTS

Insects classified as cypermethrin resistant in the adult vial assay contained significantly higher levels of both transcripts compared with the susceptible (ranging from a factor of 3.7 to 34.9 for CYP6B8/CYP6B28 and from 5.6 to 39.6 for CYP6B9), and in individual insects both transcripts were present at similar levels. Analysis of individual males collected across ecological regions and years in Texas showed overexpression of these genes.

CONCLUSIONS

This paper is the first to identify transcriptional overexpression of CYP genes associated with pyrethroid survivorship in field-collected H. zea. This discovery will allow for greater focus on increased metabolism studies at the population level. Understanding mechanisms responsible for resistance will greatly improve the ability to monitor resistance and make better control recommendations, as metabolic resistance may threaten the success not only of pyrethroids but also of other synthetic pesticides.