Chemical Composition and Insecticidal Activity of Essential Oil from Leaves of Houttuynia cordata Against Tribolium castaneum (Coleoptera: Tenebrionidae)

Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is a major pest of stored grain environments, leading to contamination and economic damage globally. The extensive use of synthetic insecticides to control this pest raises concerns about resistance, toxicity, and environmental impacts. This study investigated the chemical composition and insecticidal potential of essential oil derived from Houttuynia cordata Thunberg leaves as a sustainable alternative. The essential oil was extracted via water distillation and analyzed using gas chromatography–mass spectrometry (GC-MS), identifying 9 major compounds. Alpha-myrcene (76.58%), alpha-ocimene (8.96%), and alpha-pinene (3.59%) were the most abundant. Bioassays were conducted to assess the contact toxicity, fumigation toxicity, and repellent activity of the essential oil against adult T. castaneum. The contact toxicity bioassay revealed increasing mortality over time, with a median lethal dose (LD50) of 30.14 µL/mg adult and an LD90 of 49.78 µL/mg adult at 72 h. The fumigation toxicity bioassay indicated a lethal median concentration (LC50) of 16.06 µL/L air and LC90 of 41.86 µL/L air at 72 h. Repellent activity bioassays demonstrated 100% at a concentration of 3.75 µL/mL after 8 h. These findings suggest that H. cordata essential oil could serve as a promising botanical insecticide for managing T. castaneum. Its strong repellent activity, along with high contact and fumigant toxicity, supports its integration into sustainable pest management strategies as a natural alternative to synthetic pesticides.