Comparative Evaluation of Pesticidal Potential of Five Aromatic Plants, with Emphasis on the Fungicidal Activity of Lavandula dentata and Thymus vulgaris Extracts Against the Soil-Borne Tomato Pathogens Fusarium oxysporum f.sp. radicis-lycopersici and Verticillium dahliae.

The transition toward a sustainable agri-food system, aligned with agricultural and environmental policy objectives, has increased interest in aromatic plants as non-synthetic pesticide alternatives. This study focused on evaluating the antifungal potential of five specific aromatic plant species, particularly Lavandula dentata, Origanum vulgare, Thymus vulgaris, Salvia officinalis and Rosmarinus officinalis, against the phytopathogenic soil-borne fungi Fusarium oxysporum f.sp. radicis-lycopersici and Verticillium dahliae. During screening, L. dentata and T. vulgaris extracts exhibited strong in vitro fungicidal activity. Bioactive compounds previously detected in both lavender and thyme were identified in their extracts using a triple quadrupole/linear ion trap mass spectrometer. Assessment of in vitro phytoprotective action of L. dentata extract in solid and liquid growth media demonstrated inhibitory effects against F. oxysporum f.sp. radicis-lycopersici at concentrations above 1% v/v, with inhibitory effects of L. dentata extract being observed at concentrations equal to or above 2% v/v. T. vulgaris extract inhibited V. dahliae growth on solid media at concentrations at 1% v/v or above, while inhibitory effects were observed in broth media containing 2% v/v thyme extract. Seed germination tests of both L. dentata and T. vulgaris revealed a concentration-dependent reduction in their germination index (GI) at concentrations equal or above 2% v/v, apart from the effect of lavender extract on cress, where inhibition occurred at dose application above 5% v/v. In planta experiments demonstrated the complete phytoprotective action of lavender extract against F. oxysporum f.sp. radicis-lycopersici, while a marginal improvement in plant survival was observed during application of T. vulgaris extract.