IN VITRO EFFECT OF PLANT ESSENTIAL OILS ON GROWTH OF SOME SOIL-BORNE PATHOGENS

A study of antifungal and antibacterial activity of 17 commercially available essential oils was carried out in vitro using cultures of Pythium sp., Fusarium oxysporum f. sp. lycopersici, F. oxysporum f. sp. pisi, Verticillium albo-atrum, Rhizoctonia sp. and Clavibacter michiganensis subsp. michiganensis as test organisms. The cultures, grown on artificial media in petri dishes, were exposed to volatile phase of the oils for seven days. The growth rate of the pathogens was partially or completely inhibited by all the essential oils at concentrations up to 0.65 µl/ml of air. Cinnamon, thyme, basil, and fenchel essential oils showed fungicidal and bactericidal effect on all the tested pathogens at the concentration of 0.16 µl/ml of air. However, turpentine, orange, and bergamot orange oils, at a concentration 0.65 µl/ml of air or lower, were not lethal for any of the pathogens. V. albo-atrum was the most sensitive pathogen in this study, while both formae speciales of F. oxysporum showed moderate level of tolerance to the majority of the investigated oils. The results indicated that some of the tested essential oils could be used for the control of investigated soil-borne pathogens.