Lemongrass [Cymbopogon citratus (DC.) Stapf.] Oil: Potential Biocontrol Agent against Major Fungal Pathogens of Gumamela (Hibiscus rosa-sinensis L.)

Lemongrass [Cymbopogon citratus (DC.) Stapf.] oil treatment at different volumes (10, 20, 30 and 50 mu L) was tested for its antifungal activity in vitro and in vivo against Colletotrichum gloeosporioides, Fusarium moniliforme and Rhizoctonia solani, the fungal pathogens isolated from gumamela (Hibiscus rosa-sinensis L.). The efficacy of the extracted lemongrass oil was compared with 30 mu L of 100 ppm Benomyl, a broad spectrum systemic fungicide. The in vitro assay showed that lemongrass oil significantly inhibited fungal growth at higher volumes when paper disk (at 50 mu L) or agar dilution (at 30-50 mu L) techniques were used. Based on in vivo assay, lemongrass oil significantly suppressed disease development in the inoculated Hibiscus plants, matching the performance of Benomyl. The bioactivity of the essential oil in its vapor phase could have made this fumigant effective in controlling the fungal pathogens. Foliar spray of lemongrass oil was found effective against C. gloeosporioides, a fungal pathogen causing foliar disease of Hibiscus.