Insecticidal of Selected Plant Extracts and Their Combined Formulation Against the American Cockroach, Periplaneta Americana

Abstract The development of resistance and eco-toxicity associated with synthetic insecticides has renewed interest in the use of plant-derived pesticides for pest management. The leaves of Hyptis suaveolens , Ocimum sanctum , and Laurus nobilis were collected, authenticated, shade-dried, and extracted with ethanol, methanol, chloroform, and hexane, after which their phytochemical properties and insecticidal activities against P. americana were evaluated. Preliminary phytochemical screening and gas chromatography‒mass spectrometry analysis revealed a greater disparity in the chemical composition, and the differences found based on solvent type were attributed to the recovery of an extensive range of bioactive compounds by the different solvents. The major constituents are β-caryophyllene and germacrene D in H. suaveolens , eugenol in O. sanctum , and 1,8-cineole from L. nobilis . The contact toxicity bioassay revealed that the leaf extracts of all the plants induced mortality in the adults of P. americana , and the degree of toxicity of the solvent extracts differed among the plant species. Probit analysis confirmed the screening results and identified the combined formulation as the most effective treatment, with a 24-h LC 50 of < 5.00 mg/mL. The methanolic extract of H. suaveolens was the most potent among the individual extracts, with an LC 50 of 6.19 mg/mL, followed by O. sanctum methanol (7.17 mg/mL), H. suaveolens ethanol (7.88 mg/mL), L. nobilis methanol (8.33 mg/mL), O. sanctum ethanol (8.74 mg/mL), and H. suaveolens chloroform (12.02 mg/mL). The results indicate a promising avenue for H. suaveolens against P. americana and a combined formulation for developing a botanical insecticide formulation against P. americana .