Botanical Oils Isolated from Simmondsia chinensis and Rosmarinus officinalis Cultivated in Northern Egypt: Chemical Composition and Insecticidal Activity against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst)

Abstract

The rice weevil, <i>Sitophilus oryzae</i> (L.), and the red flour beetle, <i>Tribolium castaneum</i> (Herbst), are key stored-product pests in Egypt and worldwide. The extensive use of synthetic insecticides has led to adverse effects on the environment, human health, and pest resistance. As a result, environmentally friendly pest management alternatives are desperately required. The botanical oils of jojoba, <i>Simmondsia chinensis</i> (L.)<i>,</i> and rosemary, <i>Rosmarinus officinalis</i> L. plants growing in Egypt were extracted, identified by gas chromatography/mass spectrometry (GC-MS), and evaluated for their insecticidal activity against <i>S. oryzae</i> and <i>T. castaneum</i>. The main constituents identified in BOs were carvyl acetate (20.73%) and retinol (16.75%) for <i>S. chinensis</i> and camphor (15.57%), coumarin (15.19%), verbenone (14.82%), and 1,8-cineole (6.76%) for <i>R. officinalis.</i> The <i>S. chinensis</i> and <i>R. officinalis</i> BOs caused significant contact toxicities against <i>S. oryzae</i> and <i>T. castaneum</i> adults, providing LC₅₀ values of 24.37, 68.47, and 11.58, 141.8 ppm at 3 days after treatment (DAT), respectively. <i>S. chinensis</i> oil exhibited significant fumigation toxicity against both insects; however, it was more effective against <i>S. oryzae</i> (LC₅₀ = 29.52 ppm/L air) than against <i>T. castaneum</i> (LC₅₀ = 113.47 ppm/L air) at 3 DAT. Although the essential oil (EO) of <i>R. officinalis</i> significantly showed fumigation toxicity for <i>S. oryzae</i> (LC₅₀ = 256.1 and 0.028 ppm/L air at 1 and 3 DAT, respectively)<i>,</i> it was not effective against <i>T. castaneum</i>. These BOs could be beneficial for establishing IPM programs for suppressing <i>S. oryzae</i> and <i>T. castaneum</i>.