Optimization of antifungal and insecticidal effects of garden thyme (Thymus vulgaris L.) essential oil through response surface methodology

In the present study, optimization and modeling of the mycelial growth inhibitory and fumigant toxicity of Thymus vulgaris essential oil were investigated using Response Surface Methodology (RSM) against the pathogenic fungi Fusarium graminearum and Botrytis cinerea and the lesser grain beetle (Rhyzopertha dominica), respectively. The chemical composition of this essential oil was also assessed through Gas Chromatography-Mass Spectrometry (GC-MS) and carvacrol (27.99%), thymol (12.76%), and geraniol (8.91%) were identified as its main components. Mycelial growth inhibition of pathogenic fungi and insect pest mortality was significantly enhanced with increasing of the essential oil concentrations and the exposure times. Optimum conditions to achieve maximum mycelial growth inhibitory (88.67%) were evaluated as time of 88.59 h and the concentration of 486.66 ppm. Also, a time of 74.01-h and the concentration of 552.96 ppm were caused the maximum growth inhibitory of B. cinerea (94.43%). The concentration of 43.10 µl/l and 60 h exposure time were estimated as optimum conditions for achieving 72.23% mortality of R. dominica. Results demonstrated that the essential oil of T. vulgaris has a high potential for management of F. graminearum and B. cinerea and the lesser grain beetle