Toxicity of Hypaconitine from Aconitum coreanum (H. Lév.) Rapaics Against the Oriental Armyworm, Mythimna separata (Walker)

<i>Mythimna separata</i> (Walker) (Lepidoptera: Noctuidae) is a major migratory pest causing severe damage to cereal crops such as maize, wheat, and rice across Asia, and is also found in many parts of Oceania. With increasing insecticide resistance, botanical alternatives are urgently needed. This study evaluated the insecticidal potential of hypaconitine, a C19-diterpenoid alkaloid from <i>Aconitum coreanum</i>, against <i>M. separata</i> larvae. Hypaconitine exhibited significant stomach toxicity and strong antifeedant activity. It also caused pronounced growth inhibition, prolonged larval and pupal development, reduced pupation and adult emergence, induced morphological deformities, and significantly shortened adult longevity. Crucially, biochemical assays revealed sustained, time- and concentration-dependent upregulation of key detoxification enzymes-carboxylesterase (CarE), glutathione S-transferase (GST), and cytochrome P450 (CYP450)-over 72 h, indicating that hypaconitine imposes severe metabolic fitness costs rather than being readily detoxified. These effects collectively demonstrate that hypaconitine's insecticidal efficacy arises not only from direct toxicity but also from exploiting the physiological trade-offs inherent in xenobiotic defense. Its multi-modal action-combining larvicidal, antifeedant, growth-regulatory, and metabolism-disrupting effects-presents a novel strategy for bioinsecticide development with a lower risk of resistance evolution. These findings highlight hypaconitine as a promising candidate for sustainable, integrated management of <i>M. separata</i> and other resistant lepidopteran pests.