Toxicity of Ten Native Edible and Essential Plant Oils Against the Granary Weevil, Sitophilus granarius L. (Coleoptera: Curculionidae)

Document Type : Original Article

Authors

1 Department of Zoology, Faculty of Science, Sohag University,Sohag, Egypt

2 Entomology Department, Faculty of Science, Benha University, Cairo, Egypt

Abstract

The comparative toxicity of ten selected native essential and edible oils was assessed against S. granarius. The oils used are black seed oil (Nigella sativa), Sesame oil (Sesamum indicum), olive oil (Olea europaea), Peppermint oil (Mentha piperita), Basil Oil (Ocimum basilicum), orange oil (Citrus sinensis), Rosemary oil (Rosmarinus officinalis), Clove oil (Dianthus caryophyllus), Garlic oil (Allium sativum), and Cinnamon oil (Cinnamomum zeylanicum). Different concentrations of oils were mixed with wheat grains and provided for adults in test tubes. Mortalities were recorded for 3 days post-treatment. The overall results showed that Garlic oil was the most toxic and Rosemary was the least toxic among both edible and essential oils.  A direct correlation was found between oil dose and percent mortality of adults under all exposure periods.  The recorded values of LC50 and the toxicity index showed that Sesame oil was the most toxic edible oil followed by Black seed and Olive oils.  The essential oils used can be arranged in descending order according to their toxicities to S. granarius adults as follows: Garlic > clove > Cinnamon > Basil > Orange > Peppermint> Rosemary. All the fixed and essential oils used, demonstrated satisfactory activity and proved to be promising as control agents of S. granaries and consequently other similar stored product insects. Some oils were highly toxic at low concentration and short exposure time; whereas some oils might be required in higher concentrations and longer exposure time to achieve satisfactory control of the insects.

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