Aims: To develop a natural fungicide against aflatoxigenic fungi, to protect stored rice, using the essential oil of lemongrass. Methods and Results: Aspergillus flavus Link. was isolated from stored rice and identified as an aflatoxigenic strain. Lemongrass oil was tested against A. flavus and the test oil was fungistatic and fungicidal against the test pathogen at 0AE6 and 1AE0 mg ml )1 , respectively. Aflatoxin production was completely inhibited at 0AE1 mg ml )1 . The results obtained from the thin layer chromatographic bioassay and gas chromatography indicated citral a and b as the fungicidal constituents in lemongrass oil. During the fumigant toxicity assay of lemongrass oil, the sporulation and the mycelial growth of the test pathogen were inhibited at the concentrations of 2AE80 and 3AE46 mg ml )1 , respectively. Conclusion: Lemongrass oil could be used to manage aflatoxin formation and fungal growth of A. flavus in stored rice. Significance and Impact of the Study: Currently, fungicides are not used to control fungal pests or mycotoxin production on stored rice. Rice treated with the essential oil of lemongrass could be used to manage fungal pests as well as the insect pests in stored rice. The essential oil is chemically safe and acceptable to consumers, as synthetic chemical fungicides can cause adverse health effects to consumers.

The essential oils of the leaves of Cymbopogon citratus, Cymbopogon nardus, Cinnamomum zeylanacum and rhizome ofAlpinia 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,s-cine01 in A. calcarata. In a dual choice repellency test, repellency to S. oryzae increased with increasing dose of each oil except C. zeylanicum a t a dose of 1 mg. Cymbopogon citratus was the most toxic oil to S. oryzae during the fumigant toxicity test with an LC,, value of 0:035 gA. Adults ofS. oryzae were equally susceptible to the fumigant toxicity of C. nardus and C. zeylanicum a t 0.1 gll level. Furthermore, S. oryzae adults were tolerant to the contact (0.15 g/m2) and fumigant (0.1 g/l) activities ofA. calcarata oil and the mortality of the test insects was not significantly different from the controls.