Evidence of field‐evolved resistance to Cry1Ac‐expressing <i>Bt</i> cotton in <i>Helicoverpa armigera</i> (Lepidoptera: Noctuidae) in northern China

Abstract

This study documented a case of field-evolved resistance in H. armigera after several years of intensive planting of Bt cotton. Proactive tactics must be adopted to prevent further increase of resistance gene frequency in the Qiuxian region.