Biocontrol of strawberry pathogen Botrytis cinerea using plant extracts and essential oils

Essential oils and plant extracts of the rosemary (Rosmarinus officinalis L.), bay-laurel (Laurus nobilis L.) and clove (Syzygium aromaticum L.) contain various valuable compounds that provide antimicrobial and antifungal properties. As a result, they have the potential to be used in plant-pathogen control. Botrytis cinerea is one of the main strawberry pathogens, which infects plants during various stages of growth. The study aimed to evaluate the efficacy of plant extracts and essential oils of rosemary, bay-laurel and clove, and their mixtures against B. cinerea in vitro. Rosemary, bay-laurel and clove extracts and essential oils were separately and in combinations mixed with potato dextrose agar media at different concentrations. Fractional inhibition concentration (FIC) indexes were calculated for the mixtures to determine synergistic, additive or antagonistic effects of the combinations of the investigated plant extracts and essential oils. Results of the experiment showed that clove extract had the highest inhibition (100%) of B. cinerea, and rosemary essential oil had the lowest inhibition (31.91%). The mixtures, which managed to fully inhibit the growth of B. cinerea, were clove extract + clove essential oil, bay-laurel extract + clove essential oil and rosemary extract + clove essential oil. Synergy was found between bay-laurel extract and clove essential oil, and rosemary extract and essential oil, the FIC indexes were equal to 0.75 for both mixtures. The mixture of bay-laurel extract and bay-laurel essential oil was antagonistic as the FIC index was 2.5.