Control of storage diseases of apples by plant volatile compounds and hot water

The antifungal effect of four plant volatile compounds (thymol from Thymus vulgaris, eugenol from Syzygium aromaticum, cinnamon oil from Cinnamomum zeylanicum and lemongrass oil from Cymbopogon citrullus) and of hot water (48, 51, 54, and 57 C) against two postharvest diseases in apples, caused by Neofabraea perennans and Penicillium expansum, was tested in vitro and in vivo. Lemongrass oil or a mixture of thymol (60 mg L-1) and eugenol (3 g L-1) reduced infection with N. perennans and P. expansum by 40-46% and 41-45%, respectively, in artificially inoculated apples ('Amorosa') compared with non -treated apples. Hot water (48-54 degrees C) decreased infection with P expansum and N. perennans by 33 and 41%, respectively, while the hot water 57 degrees C treatment had a negative effect. A combination of thymol (60 mg L-1) and eugenol (3 g L-1) inhibited mycelial growth of both pathogens by 75-80%. Cinnamon oil and lemongrass oil also showed strong inhibition of mycelial growth of N. perennans, but not of P. expansum. Hot water treatment for 1 min decreased mycelial growth of perennans by more than 80% and of P expansum by 35-55%. No significant differences were found between the different temperatures of the hot water for N. perennans, while hot water at 54 C had the greatest effect on P expansum. Viability of N. perennans conidia was inhibited by 73 and 54%, respectively, after treatment with a combination of thymol (60 mg L-1) and eugenol (3 g L-1), or lemongrass oil. Conidia of P. expansum lost approximately 60% of their viability when treated with the thymoleugenol mixture.Control of storage diseases of apples by plant volatile compounds and hot water