Essential oils to control Alternaria alternata in vitro and in vivo

The inhibitory effects of five essential oils (thyme, sage, nutmeg, eucaptus and cassia) against Alternaria alternata were tested at different concentrations (100–500 ppm) in vitro. The cassia oil and thyme oil both exhibited antifungal activity against A. alternata. The cassia oil inhibited completely the growth of A. alternata at 300–500 ppm. The thyme oil exhibited a lower degree of inhibition 62.0% at 500 ppm. Spore germination and germ tube elongation of the pathogens in potato dextrose broth was strongly inhibited in the presence of 500 ppm cassia oil. Irreversible inhibition of fungal growth could be caused by exposure to 300 ppm and 400 ppm cassia oil for 6 days and 500 ppm cassia oil for 3 days. Cassia oil at 500 ppm reduced the percentage of decayed tomatoes. The experiments on reducing natural decay development of tomatoes gave similar results. Therefore, essential oils could be an alternative to chemicals for control of postharvest phytopathogenic fungi on fruits or vegetables.