Screening for inhibitory activity of essential oils on fungal tomato pathogen Stemphylium solani Weber

Development of crop protective products with natural origin as alternative to synthetic fungicides have been in focus, because they present low environmental impact when compared to conventional pesticides. A total of ten essential oils were chemically characterized and tested for antifungal activity against Stemphylium solani, which causes gray leaf spot on tomato. All essential oils showed antifungal activity against the fungus tested. Essential oils of Aloysia citrodora (citral) and Eucalyptus staigeriana (citral), Cinnamomum camphora (linalool) and Foeniculum vulgare (anethole), proved to be the most effectives, showing 100% inhibition of mycelial growth at maximum concentration of 2.5 µL mL-1. Essential oils were also evaluated for their phytotoxicity on tomato. Volatile effect of E. staigeriana, Eucalyptus globulus and Baccharis trimera oils reduced seedling growth, however the other tested oils had no volatile effect on tomato seeds and seedlings. Contact effect of all essential oils presented negative response on germination of seeds and development of seedlings. Thus, the essential oils used in this study presented fungicidal action and could be used for the development of new environmental friendly products for controlling phytopathogen on tomato, however further formulation and field application form are necessary to achieve this target.