Chemical composition and insecticidal activity of Nepeta italica L. extracts against Sitophilus granarius (L. Linnaeus, 1758) (Coleoptera: Curculionidae) and Tribolium confusum Jacquelin du Val, 1863 (Coleoptera: Tenebrionidae)

Abstract

This study was carried out to determine the insecticidal activities of Nepeta italica L. (Lamiaceae) extracts against Sitophilus granarius (Linnaeus, 1758) (Coleoptera: Curculionidae) and Tribolium confusum Jacquelin du Val, 1863 (Coleoptera: Tenebrionidae) pests along with chemical composition of the active extract. Topical and contact activity of three different extracts (hexane, n-butanol, water) of N. italica were evaluated against adults of the two pests. Chemical constituents of the active (hexane) extract were identified by gas chromatography-mass spectrometry (GC/MS) apparatus. The major compounds were determined as 2-tert-Butyl-6-methyl-phenol (4.94%), nonadecane (4.78%), 1,9-diepipresilphiperfolane-9,15-epoxide (4.47%), neophytadiene (3.49%) and palmitic acid (3.36%). It was found out that the concentration required to kill S. granarius adults (LC50: 758.343 ppm) after 96 h in topical application using hexane extracts was higher than the concentration required to kill T. confusum adults (LC50: 509.988 ppm). Likewise, when mortality times at the highest concentration were compared, the time required to kill S. granarius adults (LT50: 34.07 h) was found to be longer than the time required to kill T. confusum adults (LT50: 26.15 h). The results showed that N. italica hexane extract was highly effective in both application methods and it could be suggested to use as an alternative natural bioinsecticide in the management of these pests.