The aim of this study was to find an alternative to synthetic fungicides currently used in the control of
devastating fungal pathogen Botrytis cinerea, the causal agent of grey mould disease of tomato. Antifungal
activities of essential oils obtained from aerial parts of aromatic plants, which belong to the Lamiacea family
such as origanum (Origanum syriacum L. var. bevanii), lavender (Lavandula stoechas L. var. stoechas) and
rosemary (Rosmarinus officinalis L.), were investigated against B. cinerea. Contact and volatile phase effects of
different concentrations of the essential oils were found to inhibit the growth of B. cinerea in a dosedependent
manner. Volatile phase effects of essential oils were consistently found to be more effective on
fungal growth than contact phase effect. A volatile vapour of origanum oil at 0.2 μg/ml air was found to
completely inhibit the growth of B. cinerea. Complete growth inhibition of pathogen by essential oil of
lavender and rosemary was, however, observed at 1.6 μg/ml air concentrations. For the determination of the
contact phase effects of the tested essential oils, origanum oil at 12.8 μg/ml was found to inhibit the growth
of B. cinerea completely. Essential oils of rosemary and lavender were inhibitory at relatively higher
concentrations (25.6 μg/ml). Spore germination and germ tube elongation were also inhibited by the
essential oils tested. Light and scanning electron microscopic (SEM) observations revealed that the essential
oils cause considerable morphological degenerations of the fungal hyphae such as cytoplasmic coagulation,
vacuolations, hyphal shrivelling and protoplast leakage and loss of conidiation. In vivo assays with the
origanum essential oil, being the most efficient essential oil, under greenhouse conditions using susceptible
tomato plants resulted in good protection against grey mould severity especially as a curative treatment. This
study has demonstrated that the essential oils are potential and promising antifungal agents which could be
used as biofungicide in the protection of tomato against B. cinerea.