In Vitro Efficacy of <i>Thymbra capitata</i> (L.) Cav. Essential Oil Against Olive Phytopathogenic Fungi

In recent years, the excessive use of pesticides has raised environmental and health concerns, which has led to research into natural alternatives. Essential oils may represent a sustainable solution to this problem. In this study, essential oils from <i>Thymbra capitata</i> (L.) Cav., <i>Eucalyptus globulus</i> Labill, and <i>Mentha piperita</i> L. were analyzed by GC–MS and tested in vitro using the poisoned food technique against six olive pathogen fungi: <i>Alternaria</i> sp., <i>Arthrinium marii</i>, <i>Colletotrichum acutatum</i>, <i>Fomitiporia mediterranea</i>, <i>Fusarium solani</i>, and <i>Verticillium dahliae</i>. <i>T. capitata</i> essential oil (0.1 g/L) showed the highest antifungal activity when compared to <i>E. globulus</i> and <i>M. piperita</i> essential oils, which exhibited significantly lower efficacy against the tested olive phytopathogenic fungi. GC–MS analysis revealed that carvacrol is the main compound (76.1%) in <i>T. capitata</i> essential oil. A comparison of the inhibitory effect of <i>T. capitata</i> essential oil (0.1 g/L) and carvacrol (0.07 g/L) on selected fungal strains showed similar results, with carvacrol slightly more effective, although the differences were mostly statistically insignificant, except for <i>C. acutatum</i>. To the authors knowledge, this is the first study demonstrating the inhibitory effect of <i>Thymbra capitata</i> essential oil against <i>A. marii</i> and <i>F. mediterranea.</i> The results of this study represent a basis for the development of new biochemical biopesticides based on <i>T. capitata</i> essential oil as a useful tool for the contrast of some fungal olive tree diseases.