oils extracted from cymbopogon citratus, lantana camara, artemisia camphorata, and imperata cylindrica plants were used as potential insecticides against the rice weevil, sitophilus oryzae (l.) (coleoptera: curculionidae). the phytochemical composition of the isolated oils was identified by gas chromatograph-mass spectrometry (gc-ms). oil contact toxicities were evaluated against the adults of s. oryzae. the activities of acetylcholinesterase (ache), alkaline phosphatase (alp), and transaminases enzymes (ast) were measured. l. camara oil (lc50 = 9.81 mg/cm2) demonstrated the highest effect, followed by c. citratus oil (lc50 = 10.89 mg/cm2), a. camphorata eo (lc50 = 16.12 mg/cm2), and i. cylindrica oil (lc50= 36.85 mg/cm2) against the adults of s. oryzae. the inhibition percentages of ache were 38.8, 41.7, 35.0, and 27.2%; alp were 42.4, 49.3, 28.1, and 18.7%; ast were 33.9, 38.7, 20.8, and 11.8%; and alt were 22.7, 30.5, 14.6, and 9.6% after treated s. oryzae with oils from c. citratus, l. camara, a. camphorata and i. cylindrica, respectively. the highest abundant compounds in c. citratus were geranial (25.95%), nerylacetal (8.85%), and neral (8.45%), in l. camara were caryophyllene (12.2%), and 3-elemene (8.89%), in a. camphorata were germacrene d-4-ol (20.83%), and borneol (19.47%), and in i. cylindrica were 5-phenylundecane (10.68%), and 6-phenyldodecane (8.70%).