Fumigant toxicity of volatile natural products from Korean spices and medicinal plants towards the rice weevil, Sitophilus oryzae (L)

The fumigant toxicity of various volatile constituents of essential oils ex tracted from sixteen Korean spices and medicinal plants towards the rice we evil, Sitophilus oryzae L (Coleoptera: Curculionidae), was determined. The most potent toxicity was found in the essential oil from Mentha arvensis L var piperascens (LC50 = 45.5 mul litre(-1) air). GC-MS analysis of essentia l oil fi om M arvensis showed it to be rich in menthol (63.2%), menthone (1 3.1%) and limonene (1.5%), followed in abundance by beta -pinene (0.7%), al pha -pinene (0.6%) and Linalool (0.2%). Treatment of S oryzae with each 12. 7 mul litre(-1) air) followed by linalool (LC50 = 39.2 mul litre(-1) air) a nd alpha -pinene (LC50 = 54.9 mul litre(-1) air). Studies on inhibition of acetylcholinesterase activity of S oryzae showed menthone to have a nine-fo ld lower inhibitory effect than menthol, despite menthone being 8.1-fold mo re toxic than menthol to the rice weevil. Different modes of toxicity of th ese monoterpenes towards S oryzae are discussed. (C) 2001 Society of Chemic al Industry.