Olonisakin Adebisi
Adekunle Ajasin University, Nigeria
Posters-Accepted Abstracts: Nat Prod Chem Res
The composition of terpenoids in essential oils determines the activity of the oil. The continuous usage of synthetic insecticides causes serious problems including development of resistance by insect, pollution of environment and side effects on human. Therefore, plant essential oils have proved to be alternative to the synthetic insecticides because they can easily degrade in the environment and harmless to non targeted organism. Also, appropriate formulations that will increase the length of the activity of the volatile oils are important and must be put into consideration. The chemical composition of the essential oil obtained by steam distillation from the aerial parts of Citrus aurantifolia was analyzed by Gas Chromatography (GC). Toxicity and repellency of the oil on cowpea bruchid Callosobruchis maculates (F) (Coleoptera, Bruchidae) was carried out using standard methods. Formulations of the oil were carried out using kaolin and bentonite as carriers. Thirty seven components of the essential oil were identified with limonene (82.55%), β-myceme (6.56%), cymene (1.34%) and thymol (1.09%) as major components. Other volatile compounds that are not terpenoids were also found like furan, non-anal and some acetate. The toxicity and repellency of the oil were concentration dependent. Acute toxicity ranged between 13.33%-91.66% at 5 μml to 17.5 μml per 5 g seed, respectively and the percentage repellency ranged between 57.30%-87.30% from 2.5 to 12.5 μl/30 cm2. The activity of the formulations reduced with time when using bentonite as carrier but kaolin was found to have toxic effect on insects without oil. Limonene was found to be the main terpenoids. The essential oil repelled the insects and there was acute toxicity with LC50 10.68 μL/5 g seed. The formulations of bentonite were poor. Kaolin was found to be active even without oil but there was increase in mortality with the treated kaolin
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