No 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 LC 50 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.

The development of nano-insecticides has attracted much interest in the last decade because it has the potential to result in an alternative pestmanagement strategy and also reduce the risk of chemically based insecticides.Herein, native rosemary (Rosmarinus officinalis) and black seed (Nigella sativa) oils were utilized for preparing their nanoemulsions by spontaneous emulsification method in the presence of tween 80 as a structure-directing agent. The prepared nanoemulsions were explored for granary weevil, Sitophilus granarius (L.), adults control and compared with their oils. Within the typical droplet sizes of 100 and 224 nm, both rosemary and black seed nanoemulsions were found to be physically and thermodynamically stable. The insecticidal activity of the nanoemulsions was higher than that of the crude oils. After 24 h of exposure, the LD 50 values of rosemary and black seed nanoemulsions were estimated to be 102.56 and 35.08 µg/g, respectively, compared to 188.95 and 210.09 µg/g of their oils. These results revealed that the droplet size and chemical composition of the nanoemulsion are the significant factors that affect their toxicity. Surprisingly, the nanoemulsions had no effect on seed germination at LD 50 or even LD 99 . The utilization of such nanoformulations might open up a new avenue for ecofriendly pest control that is not damaging to humans or the environment, as well as a growing agricultural economy.