Determination of in vitro antifungal activity of some plant essential oils against botrytis cinerea and trichothecium roseum on hazelnut

Botrytis cinerea and Trichothecium roseum cause yield and quality losses in hazelnuts, especially in fruits and fruit clusters. In this study, the antifungal activities of essential oils of thyme (Thymus vulgaris L.), peppermint (Mentha piperita L.), lavender (Lavendula angustifolia Mill.), sage (Salvia officinalis L.) and bay laurel (Laurus nobilis L.) against these pathogens were investigated in vitro under contact and vapor phase conditions. Doses of 15, 30, 60, 90, and 120 μL/petri dish were used to determine the effects of plant essential oils on mycelial development and conidal germination in the vapor phase, while doses of 1, 2, 4, 6, and 8 μL/ml were used to determine the contact effects. Two additional sub-doses of thyme essential oil (3.75 and 7.5 μL/petri for the vapor phase, and 0.25 and 0.50 μL/ml for the contact effect) were included in the experiment. The inhibition rates (%) of essential oils on mycelial growth and conidia germination of fungi and then EC50 values were calculated. Thyme essential oil, which demonstrated 100% efficacy in all 5 routine doses, also demonstrated 100% contact efficacy against B. cinerea conidal germination at 3.75 μL/petri. Bay laurel essential oil was 100% effective at the highest doses in inhibiting conidal germination in the contact phase, while the highest efficacy was achieved at the third dose in the vapor phase. Lavender inhibited T. roseum conidal germination at the third dose, while the efficacy for B. cinerea at the fifth dose was 92.33%. In terms of mycelial growth, 100% efficacy was observed at the third dose in both phases. Peppermint essential oil showed 100% efficacy in both the contact and vapor phases in the first two doses, while its efficacy in conidia germination reached 100% in the second dose. Sage essential oil yielded lower efficacy values compared to the other oils, but 100% efficacy was achieved in all applications at the highest dose. Because thyme and peppermint essential oils showed high activity in inhibiting mycelial growth of both agents, even at low doses, in the vapor phase, EC50 values could not be calculated. However, these values were determined to be 3.30 and 3.09 for B. cinerea and 0.07 and 3.96 for T. roseum, respectively, for conidia germination. The EC50 values of thyme essential oil in the contact phase for mycelial growth of both agents were 0.18 and 0.14 μL/ml, respectively, while values for conidia germination could not be calculated. The EC50 values of peppermint essential oil in the vapor phase for mycelial growth and conidia germination of B. cinerea could not be calculated, while these values were determined to be 2.26-6.20 for the other essential oils. Keywords: Botrytis cinerea, Trichothecium roseum, Essential Oil, Hazelnut