Chemical composition and insecticidal activity of the essential oil of Cymbopogon flexuosus against Bemisia tabaci

Abstract

The essential oil isolated by hydro-distillation method from the leaves of Cymbopogon flexuosus was analyzed by GC-FID and GC-MS. Twenty-three compounds constituting of 98.72% compounds of the oil were identified. The major compounds were identified as geranial (47.3%), neral (34.7%), geraniol (3.76%), neryl acetate (3.17%) and β-caryophyllene (1.62%). Citral (94.68%), a mixture of neral (42.52%) and geranial (52.16%) was also isolated from the lemongrass oil. Lemongrass oil and citral were found to have dose dependent contact toxicity and ovipositional deterrent activity against Bemisia tabaci. The mortality due to lemongrass oil and citral ranged from 31.77 to 88.79% and 35.2 to 90.12% and 25.16 to 79.15 % & 28.58 to 82.2% after 24 and 48 hr of treatments at 0.07 to 0.9% concentrations as compared to control, in which 15.26 to 16.42% mortality was recorded. The lemongrass oil and citral were found to have ovipositional deterrent activity against B. tabaci. Results also showed that minimum number of eggs laid on the leaves treated (0.05%) with oil and citral were 6.333 and 11.333 after 48hr, compared to control (29.333 to 32.667). Thus, oviposition deterrence index at 0.05% concentration of oil and citral was found to be -66.09 and -44.27. Citral was identified as a bioactive molecule, responsible for the mortality and ovipositional deterrent activity of the oil against B. tabaci.