Chemical constituents and fumigant toxicity of essential oil from Carum copticum against two stored product beetles

Plant secondary metabolites play an important role in plant-insect interactions and therefore such compounds may have insecticidal or antifeedant activity against insects. Carum copticum C. B. Clarke (Apiaceae) is one of these plants that have medicinal effects on humans. The chemical composition of the essential oil from dry seeds of C. copticum was studied by gas chromatography (GC) and gas chromatography mass spectrometry (GC-MS). Thymol (41.34%), alpha-terpinolene (17.46%) and rho-cymene (11.76%) were found to be the major constituents of the oil. In fumigant toxicity tests with the essential oil against adults of Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) at 27 +/- 1 degrees C and 60% +/- 5% RH, it was observed that S. oryzae (LC50 = 0.91 mu L/L) were significantly susceptible than T. castaneum (LC50 = 33.14 mu L/L). The mortalities of the insect species reached 100% at concentrations higher than 185.2 mu L/L and 12-h exposure time. The findings indicate the strong insecticidal activity of C. copticum oil and its potential role as a fumigant for stored-product insects.