Evaluation of antifungal properties of Monarda citriodora hydrolate and essential oil against certain phytopathogens and mycocomplexes

The antifungal activity of the Monarda citriodora Cerv. ex Lag. hydrolate and essential oil against an Alternaria alternata (Fr.) Keissl. isolate, obtained from infected Monarda leaves, as well as mycocomplex, developed on the lateral photosynthetic organs of the essential oil-bearing plants M. didyma L. and M. fistulosa L., grown in the collection plots of the Nikita Botanical Gardens, was evaluated. In laboratory studies were performed that hydrolat showed no significant inhibitory effect on fungal phytopathogen. The essential oil of the thymol chemotype (thymol 62.84%, carvacrol 7.20%) completely inhibited mycelial growth as concentrate and in the diluted form of 1:25 to 1:50. In the field experiments conducted on M. didyma and M. fistulosa plants naturally infected with a complex of fungal pathogens, treated the composition, comprising the diluted essential oil (1:25), did not result in a significant reduction in infection development. Phytotoxicity was observed (chlorosis, drying, leaf drop). The high antifungal activity of the essential oil in vitro is due to the dominance of phenolic compounds. The results indicate the potential of the essential oil as a biofungicide, provided that formulations are optimized to reduce phytotoxicity.

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