Chemical composition and fumigant toxicity of essential oil from Thymus daenensis against two stored product pests

Plant essential oils and their constituents are recognized as proper alternatives to fumigants. Thymus daenensis Celak is one of these plants that have medicinal properties and is endemic to Iran. The essential oil was isolated by hydrodistillation from dry leaves using a modified clevenger-type apparatus and the chemical composition of the oil was assessed via GC and GC-MS. Fourteen compounds (100% of the total composition) were identified. Thymol (57.4%), carvacrol (9.8%), β-caryophyllene (6.9%), γ-terpinene (6.7%) and p-cymene (6.3%) were found to be the major compounds of the essential oil. The fumigant toxicity of the essential oil was tested against 1-3 days old adults of Callosobruchus maculatus (F.) and Sitophilus granarius (L.) at 27 ± 1 °C and 65 ± 5% R. H. in darkness. The mortality of adults was tested at different concentrations (28.12, 40.62, 53.12 and 65.62 µl/l air) and different exposure times. At the highest concentration (65.62 µl/l air), T. daenensis oil caused 90 and 60% mortality with a 3 h exposure on C. maculatus and S. granarius, respectively. Based on LC50 values, C. maculatus (4.22 µl/l air) was significantly more susceptible than S. granarius (6.55 µl/l air). These results show the efficacy of T. daenensis oil for stored-products protection.