Small-scale farmers of Kebbi State use a range of Ocimum (Scent plant) and cymbopogon (Lemongrass) plant species to protect their grain from insect infestation. This study aim at identifying from the range of plant species, the species and method of their preparation with bioactive compounds most effective against Tribolium castaneum. The different plant samples tested were either cultivated or collected from the wild, which were prepared as either shade-dried or sun-dried and then subjected to Gas chromatography linked to mass spectrometry (GC-MS) analysis, to determine the type and amount of the different active compounds in the sample of the plants. The bioactivity of the different plant preparation on the insect was tested. The result of the chemical analysis indicated that the plant species collected in different places have deferring chemical compounds and ratio that can be used to distinguish one from another, which consequently affect their bioactivity against T. castaneum. Chemical analysis and bioassay indicated that Ocimum species and drying methods used affected repellency; cultivated Ocimum significantly repelled more beetles than the wild type and shade-dried plants repelled more beetles than sun-dried. This study highlights the potential of cultivated shade-dried O. basilicum in giving a better grain protection from the beetle infestation than the wild sun-dried plant

Keywords: Bioactivity, Ocimum, Cymbopogon, grain protectant, Tribolium