Abstract The essential oil of the leaves of Artemisia nilagirica from South India was investigated by GC and GC/MS, which lead to the identification of 59 compounds including Î±-thujone (41.9%), borneol (10.8%), and Î²-thujone (9.1%). The leaf oil inhibited the growth of the plant pathogen Phytophthora capsici. This property has been attributed to the presence of thujones in the oil.