Insecticidal and behavioral effects of Dysphania ambrosioides seed essential oil against Tribolium castaneum under laboratory and simulated storage conditions

This study aims to evaluate the chemical composition, antifeedant, repellent, fumigant, contact, and topical toxicity of Dysphania ambrosioides seeds EO (DAEO) against adult Tribolium castaneum, a major stored product insect. The repellency under simulated storage conditions and the acute toxicity to female rats were also assessed. GC-MS analysis revealed that DAEO was characterized by high levels of ascaridole (49,52 %), α-terpinene (17,98 %), and ρ-cymene (11,96 %). In insecticidal bioassays, the LC₅₀ values after 24 h were 39.8 μL/L air for fumigation, 0.069 μL/cm² for contact, and 0.090 μL/insect for direct application. The results from the antifeedant bioassay showed that DAEO significantly decreased all nutritional indexes starting from the lowest concentration, with a 56.3 % feeding deterrence index (FDI) and a 2.7-fold reduction in the relative consumption rate (RCR) at 0.32 μL/pellet. Contact exposure to non-lethal concentrations demonstrated strong FDI, reaching 99 % after 24 h at 0.031 μL/cm². In the repellency bioassay, DAEO exhibited a strong repellent effect with 88 % and 62 % of PR (percentage of repellency) observed after 4 and 24 h, respectively, at the lowest concentration of 0.016 μL/cm². Under simulated storage conditions, strong repellency was observed, with the proportion of insects in treated bags approximately half that in control bags after 24 h. However, this activity decreased after 72 h. Regarding acute toxicity, a dose of 10 μL/kg showed no signs of toxicity or weight loss in female rats. This study highlights the multifaceted effects of DAEO, safety, and its effectiveness under simulated storage conditions, suggesting that this EO can be considered as a promising candidate to develop an eco-friendly insecticide for controlling T. castaneum.