Fumigant Toxicity of Essential Oils of Nine Plant Species from Asteraceae and Clusiaceae against Sitophilus granarius (L.) (Coleoptera: Curculionidae)

Essential oils obtained from nine different plant species (Achillea coarctata Poir., Achillea gypsicola Hub.-Mor., Artemisia dracunculus L., Artemisia vulgaris L., Helichrysum plicatum Dc., Tanacetum agrophyllum (L.), Taraxacum officinale (L.) (Asteraceae), Hypericum scabrum L. and Hypericum perforatum L. (Clusiaceae)) were tested against adults of Sitophilus granarius (L.) (Coleoptera: Curculionidae). Results clarified that essential oils of A coarctata, A gypsicola, T. agrophyllum, H. scabrum and H. perforatum had highest insecticidal effects on S. granarius adults, compared with the control. Mortality rate of S. granarius adults increased significantly (p<0.01), as the dosage level and/or exposure time increased. Treatments with the essential oils of A coarctata, A gypsicola, A dracunculus, T. agrophyllum, H. scabrum and H. perforatum showed high levels of mortalities in S. granarius adults, when they were applied at the higher tested concentrations (10 & 20 mu l) at all post treatment periods or at a moderate concentration (5 mu l) with a long exposure period (48 or 96 h). The essential oils of A. vulgaris, H. plicatum and T. officinale had either very low or no effects. Mortality percentages of S. granarius adults, after 96 h of exposure at the maximum dose (20 mu l essential oil) of A coarctata, A gypsicola, A. dracunculus, H. scabrum, H. perforatum, T agrophyllum, H. plicatum A. vulgaris and T officinale attained 100, 100, 100, 100, 100, 98.99, 83.84, 23.23, and 18.18%, respectively. No mortality was recorded in the control. After 96 h of treatment, highest levels of mortalities (95.96 %) were recorded at the dose of 1 mu l essential oil of H. perforatum They were (84-100 %) at the dose of 5 mu l of the essential oils of A coarctata, A gypsicola, A. dracunculus, T. agrophyllum and H. perforatum, (93.94 %) at the dose of 10 mu l for H. scabrum and (83.84 %) at the dose of 20 mu l for H. plicatum.