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

Simple SummaryThe oriental armyworm (Mythimna separata) is a highly destructive migratory pest threatening cereal crops. With rising insecticide resistance and environmental concerns, novel bio-based alternatives are critically needed. This study evaluates hypaconitine—a diterpenoid alkaloid derived fromAconitum coreanum—for its insecticidal potential. We demonstrate that hypaconitine acts not only as a potent stomach poison and antifeedant, but also exploits a key physiological vulnerability in the pest: the high metabolic cost of sustained detoxification. Treated larvae exhibit prolonged development, severe pupal deformities, reduced adult emergence, and shortened lifespan—classic signs of fitness loss. Biochemical analyses confirm strong, prolonged induction of detoxification enzymes (CarE, GST, CYP450), indicating that the insect’s own defense response becomes a liability. By turning the pest’s detoxification system against itself, hypaconitine disrupts multiple life stages with a multi-modal mode of action that reduces the likelihood of rapid resistance evolution. These findings position hypaconitine as a promising, eco-friendly lead compound for next-generation bioinsecticides targeting resistant lepidopteran pests.Mythimna separata(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 fromAconitum coreanum, againstM. separatalarvae. 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 ofM. separataand other resistant lepidopteran pests.