Mortality and Repellency Effect of Some Essential Oils against Tribolium castaneum (Coleoptera: Tenebrionidae)

Abstract

The red flour beetle (Tribolium castaneum) is a major pest of stored grains, causing significant economic losses. In recent years, essential oils have gained attention as eco-friendly alternatives to synthetic pesticides. This study evaluated the insecticidal and repellent properties of three essential oils—lavender (Lavandula spica), mogra (Jasminum sambac), and rose (Rosa damascena)—against T. castaneum. Toxicity was assessed using direct contact and fumigation methods, targeting adult T. castaneum, respectively. Repellency was tested on larvae using filter paper assays and bioassays were conducted at varying doses and exposure durations. In direct contact assays, adult mortality increased with higher doses and longer exposure times. Lavender oil showed the highest toxicity (LD50 = 0.366–0.143 µl/cm²), followed by Mogra oil (LD50 = 1.037–0.147 µl/cm² at 3–48 h) and rose oil (LD50 = 0.651–0.188 µl/cm²). In fumigation assays, rose oil was the most effective against the target insect (LD50 = 4.031–2.252 µl/cm² at 24–48 h), followed by lavender oil (LD50 = 4.980–3.180 µl/cm²) and mogra oil (LD50 = 7.339–5.463 µl/cm²). Overall, the direct contact method was more effective than fumigation. Repellency assays showed mogra oil exhibiting significant effects (F = 25.25, P < 0.001) and achieving 100% repellency at 0.0785 µl/cm² within 3–4 hours, whereas lavender and rose oils showed lower and statistically insignificant effects. This study highlights the potential of essential oils as biopesticides for managing T. castaneum. Mogra oil demonstrated superior efficacy in direct contact assays, while rose oil excelled in fumigation tests. These findings support the use of essential oils as eco-friendly alternatives for pest management in stored grains.