Chemical composition and fumigant activity of essential oils from six plant families against Sitophilus oryzae (Col: Curculionidae)

Within the framework of finding new fumigants, less toxic and environmentally friendly, in comparison with conventional fumigants, natural products and essential oils are considered to be alternative sources of potentially active compounds. In this context, the aim of the present study was the chemical analysis and the evaluation of fumigant toxicity against the adults of rice weevil Sitophylus oryzae of sixteen essential oils obtained from fourteen plant species. The essential oils of the species Apium nodiflorum, Bupleurum fruticosum, Crithmum maritimum, Liquidambar orientalis and Laurus azorica consisted mainly of monoterpene hydrocarbons. Oxygenated monoterpenes were the prevailing group of compounds in the essential oils of Laurus nobilis, Myrtus communis, Salvia fruticosa S. pomifera subsp. calycina, S. officinalis and Thymbra capitata. The essential oils of Cotinus coggygria, S. microphylla and Teucrium capitatum were rich in sesquiterpenes. The most active essential oils were those of T. capitata (LC50 = 3.4 mu L/L air) and S. pomifera subsp. calycina (LC50 = 4.4 mu L/L air) against S. oryzae adults. The essential oils of S. fruticosa, L. nobilis and S. officinalis were also found to be highly toxic (LC50 = 7.4-15.5 mu L/L air). Most of the other essential oils tested exhibited moderate to low toxicities (LC50 = 17.7-37.9 mu L/L air), while those of C. coggygria and S. microphylla did not exhibit any noticeable activity. Our results indicate that some essential oils, and in particular those of T. capitata and S. pomifera subsp. calycina might be promising fumigants for the control of important pests of stored grain such as the rice weevil S. oryzae.