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 extracted from sixteen Korean spices and medicinal plants towards the rice weevil, 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 essential oil fi om M arvensis showed it to be rich in menthol (63.2%), menthone (13.1%) and limonene (1.5%), followed in abundance by beta -pinene (0.7%), alpha -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) and alpha -pinene (LC50 = 54.9 mul litre(-1) air). Studies on inhibition of acetylcholinesterase activity of S oryzae showed menthone to have a nine-fold lower inhibitory effect than menthol, despite menthone being 8.1-fold more toxic than menthol to the rice weevil. Different modes of toxicity of these monoterpenes towards S oryzae are discussed. (C) 2001 Society of Chemical Industry.