Evaluation of the Insecticidal Efficacy and Toxicity of Ethanolic Leaf Extracts of Ziziphus spina-christi L., Lawsonia inermis L., and Cupressus sempervirens L. Against Adults of the Red Flour Beetle Tribolium castaneum (Herbst) (Coleoptera: enebrionida

Abstract

This study aimed to evaluate the insecticidal efficacy and toxicity of ethanolic leaf extracts of three medicinal plants, namely Ziziphus spina-christi L.,  Lawsonia inermis L. and Cupressus sempervirens L. against adults of the red flour beetle, Tribolium castaneum (Herbst), under different exposure periods (24 hours, 48 hours, and 7 days). The results demonstrated that all tested ethanolic extracts exhibited significant insecticidal activity by increasing adult mortality throughout all exposure periods. The ethanolic extract of C. sempervirens leaves showed the highest insecticidal efficacy, followed by the extract of Z. spina-christi leaves, whereas the extract of L. inermis leaves exhibited the lowest efficacy among the tested extracts. A strong positive relationship was observed between increasing extract concentration and adult mortality, as well as between exposure time and insecticidal effectiveness. At the highest concentration (2.0%) after seven days of exposure, mortality reached 83.33% for C. sempervirens, 93.33% for Z. spina-christi, and 63.33% for L. inermis. These findings indicate the cumulative and progressive action of the bioactive compounds present in the ethanolic extracts over time. Furthermore, the extracts exhibited pronounced toxic effects against adult T. castaneum, as reflected by the calculated LC₅₀ and LC₉₀ values at different exposure periods. Toxicity varied according to plant species, with the C. sempervirens extract being the most toxic, followed by Z. spina-christi, while L. inermis showed the lowest toxicity. In addition, the toxicity of all extracts increased with prolonged exposure, as evidenced by the gradual reduction in LC₅₀ and LC₉₀ values after 48 h and 7 days of treatment