Constituents of the Essential Oil of Vernonia Amygdalina as Maize Weevil Protectants
Asawalam, E. F.
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A laboratory study was conducted to determine the efficacy of Vernonia amygdalina essential oil for Sitophilus zeamais control. The experimental design was a completely randomized design with four replications. The bioactivity of the essential oil extracted by hydro distillation from leaves of Vernonia amygdalina was assessed under laboratory conditions at 27 ±2 ºC, 60-65% R.H and 12: 12h light: dark regimes for it’s biological activity against S. zeamais (Maize weevil) in maize grains. The essential oil at three levels of application was mixed with 250 g of disinfested maize in one litre volume glass jar. The individual components of the essential oil were identified through GC, GC-MS and GC- Co injection with authentic standards. The identity of a total of 17 constituent compounds of the essential oil of the plant was confirmed and their relative proportion determined. Eucalyptol (1, 8 Cineole) had the highest percentage composition in V. amygdalina essential oil (25.1%). All the treatments with the essential oil showed significant level of toxicity to the weevil. The highest dosage (0.3%) of the essential oil of the plant material tested, induced the highest mortality in the S. zeamais after 7 days. Grains treated with the essential oil extract significantly reduced the number of Progeny produced by S. zeamais, and evoked a high repellent action against the weevil. There was no observable feeding damage on grains treated with the highest dosage of the essential oil extract. It is suggested that the plant is suitable for possible exploitation in insect pest control.