Insecticidal efficacy and chemical composition of Balanites aegyptiaca (L.) Delile seed oils against Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

Abstract

Botanical pesticides are a new trend for pest management because they are an environmentally safe alternative for synthetic chemicals. The aim of this study was to investigate the insecticidal activity of desert date (Balanites aegyptiaca %#91;L.%#93; Delile) seed oils against the red flour beetle (Tribolium castaneum Herbst) and determine the oil chemical compounds by gas chromatography-mass spectrometry. Oils were extracted by chloroform, hexane, and ethanol, and they were tested on the pest by the film residue method at doses of 1.131, 0.566, 0.283, and 0.142 mg cm-2 after 12, 24, 36, and 48 h. Results showed that chloroform achieved a 100% mortality rate at 1.131 and 0.566 mg cm-2 after 12 and 36 h exposure, respectively. Meanwhile, the hexane extract caused a similar effect after 24 and 48 h at the same doses, respectively. The chloroform extract scored the lowest median lethal dose (LD50, 0.134 mg cm-2) against the pest after 48 h of exposure. This finding indicated that chloroform extract was the most toxic for T. castaneum compared with the other extracts. The results of the oil analysis revealed that (9Z,12Z)-octadeca-9,12-dienoic acid, hexadecanoic acid, (Z)-octadec-9-enoic acid, and (E)-octadec-6- enoic acid were the main components, but the concentration differed from one extract to another. These results suggest that chloroform and hexane extracts have potent insecticidal activity and could be used in grain storage to control pests.