Insecticidal activities of essential oils from leaves of Laurus nobilis L. from Tunisia, Algeria and Morocco, and comparative chemical composition

Laurus nobilis essential oils from Tunisia, Algeria and Morocco were analyzed for their chemical composition and assessed for their repellent and toxic activities against two major stored product pests: Rhyzopertha dominica and Tribolium castaneum. The three oils showed quantitative rather than qualitative differences in their chemical compositions. 1,8-cineole, linalool and isovaleraldehyde, were identified as the major common compounds whereas, alpha-pinene, alpha-terpineol, eugenylmethylether, beta-pinene, spathulenol and beta-myrcene were also well represented in all three oils. Results showed that L nobilis essential oils were repellant and toxic to adults of R. dominica and T. castaneum. Repellent and fumigant toxicities were highly dependent upon insect species and oil origin. In filter paper tests, L nobilis essential oil from Morocco was more effective compared to Tunisian and Algerian oils. RD50 values were respectively 0.013 mu l/cm(2), 0.036 mu l/cm(2) and 0.033 mu l/cm(2) for R. dominica versus 0.045 mu l/cm(2), 0.139 mu l/cm(2) and 0.096 mu l/cm(2) for T. castaneum. Moreover, fumigant activity tests showed that both R. dominica and T castaneum were more susceptible to L nobilis essential oil from Morocco than that from Algeria or Tunisia. The corresponding LC50 values were respectively 68, 99 and 113 mu l/l air for R. dominica against 172, 194 and mu l/l air for T. castaneum. Our work clearly vindicates interest in the efficacy of essential oils from plants of Mediterranean origin both as insecticides and repellents against stored product pests. (C) 2011 Elsevier Ltd. All rights reserved.