insecticidal effects of peppermint and black pepper essential oils against rice weevil, sitophilus oryzae l. and rice moth, corcyra cephalonica (st.)

background: the rice weevil, sitophilus oryzae and rice moth, corcyra cephalonica are major and cosmopolitan insect. adults of s. oryzae (male and female) and both larvae are insatiable feeders on a great variety of grains. objective: this study was conducted to estimate the insecticidal effect of essential oils from peppermint, mentha piperita l. and black pepper, piper nigrum l. against two major stored product insects.  methods: essential oils from two species of plants were obtained by clevenger-type water distillation. the major compounds in these essential oils were identified using gas chromatography-mass spectrometry and their insecticidal effect was tested against adults of the rice weevil, sitophilus oryzae l. and the 3rd instars larvae of rice moth, corcyra cephalonica (st.).  results: the major compounds found in peppermint were menthol, isomenthone, limonene and cineole and in black pepper were limonene, α and β pinene and caryophyllene. highest toxicities were observed against s. oryzae populations treated with m. piperita and p. nigrum essential oils with lc50 values of 85.0 and 287.7 µl/l air after 72 hours after commencement, respectively. in the case of c. cephalonica larvae, the lc50 values were 343.9 and 530.5 µl/l air for m. piperita and p. nigrum essential oils at 72 hours after commencement, respectively. these results are attributed to the compounds present in essential oils of m. piperita and p. nigrum. conclusion: it was resulted that m. piperita and p. nigrum oils have insecticidal effects against s. oryzae and c. cephalonica. for this reasons, the selected plant oils have potential for development of novel insecticides.