Repellency and toxicity of four essential oils to Sitophilus Oryzae L. (Coleoptera: Curculionidae)

Abstract

The essential oils of the leaves of Cymbopogon citratus, Cymbopogon nardus, Cinnamomum zeylanicum and rhizome of Alpinia calcarata grown in Sri Lanka were tested for repellent activity, fumigant toxicity and contact toxicity against Sitophilus oryzae. The major components of the essential oils were geraniol in C. nardus, citral a and b in C. citratus, eugenol in C. zeylanicum and 1,8-cineol in A. calcarata. In a dual choice repellency test, repellency to S. oryzae increased with increasing dose of each oil except C. zeylanicum at a dose of 1 mg. Cymbopogon citratus was the most toxic oil to S. oryzae during the fumigant toxicity test with an LC50 value of 0.035 g/l. Adults of S. oryzae were equally susceptible to the fumigant toxicity of C. nardus and C. zeylanicum at 0.1 g/l level. Furthermore, S. oryzae adults were tolerant to the contact (0.15 g/m2) and fumigant (0.1 g/l) activities of A. calcarata oil and the mortality of the test insects was not significantly different from the controls.