Fumigant toxicity of essential oils and their constituent compounds towards the rice weevil, Sitophilus oryzae (L.)

Toxicity of various essential oils and their volatile constituents towards the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), was de termined. The most potent toxicity was found in essential oil from eucalypt us (LD50 = 28.9 mul/l air). GC-MS analysis of essential oil from eucalyptus showed it to be rich in 1.8-cineole (81.1%), limonene (7.6%) and alpha -pi nene (4.0%). Treatment of S. oryzae with each of these terpenes showed 1,8- cineole to be most active (LD50=23.5 mul/l air). In addition to 1,8-cineole , benzaldehyde (LD50 = 8.65 mul/l air) occurring in peach and almond kernel s had a potent fumigant toxicity towards the rice weevils. Therefore, benza ldehyde and other natural volatiles could be a safer fumigant to control st ored-grain insect pests than those currently used. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.