Grain Health Protectant Activity of Essential Oils against Infestation and Damage of Haricot Bean by Zabrotes subfasciatus (Boheman)

Experiments were conducted to evaluate the efficacy of essential oils extracted from Chenopodium ambrosioides (L.), Rosmarinus officinalis (L.), Eucalyptus globulus (Labill), Trachyspermum ammi (Sprague) and Cymbopogon citratus (Stapf) against Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae) under laboratory condition (27±3°C, 50-70% RH ). The test insects were reared in glass jar and investigated on whole Awash-1 haricot bean variety grains. A standard insecticide, primiphos-methyl 5% dust and untreated control were included for comparison. The experiment was arranged in a completely randomized design in three replications. Essential oils from the above mentioned plants were admixed with the bean grains at the rate of 750 mg/150 g of seeds. The rate of primiphos-methyl was 0.125 g/150 g of seeds. The results showed that there was complete mortality (100%) of Z. subfasciatus adults within 24 hours after treatment due to C. ambrosioides, E. globulus, T. ammi and C. citratus. Application of essential oils to bean grains significantly reduced progeny production of Z. subfasciatus. Over 97% inhibition of F1 progeny production by the pest was recorded for all essential oil treatments at the highest dose of 750 mg. Application of essential oil extracts also significantly reduced the rates of haricot bean grain infestation (up to 100%) by Z. subfasciatus. Furthermore, essential oil extracts admixed to the bean grain proved to have no significant effects on the germination capacity of the treated haricot bean grains. From the current experiment it can be concluded that the tested botanicals are as effective as primiphos-methyl which gave 100% control of Z. subfasciatus and can be used for the management of the pest.