Effectiveness of Essential Oils and Their Combinations with Aluminum Starch Octenylsuccinate on Potato Storage Pathogens

Abstract

S-carvone, L-menthone, peppermint and spearmint oils were tested in vitro against Fusarium coeruleum, F. sambucinum, F. avenaceum, F. oxysporum, Alternaria solani, Rhizoctonia solani, Helminthosporium solani, Phytophthora infestans (A1 and A2 mating types), Phytophthora erythroseptica, Phoma exigua and Pythium ultimum which are causal agents of major potato storage diseases. The majority of these pathogens were completely inhibited due to pure oils, although F. sambucinum, F. avenaceum, A. solani and P. exigua were not completely inhibited by one or more pure oils. Peppermint oil was the least effective among tested oils. However, R. solani, H. solani, P. erythroseptica, and P. infestans (A1 and A2 mating types) were completely inhibited for a period of 1-18 weeks by single treatments of all four pure oils. Effects of mixtures of aluminum starch octenylsuccinate (ASOS) and L-menthol or peppermint oil on F. sambucinum and R. solani were also tested in vitro for a period of over 5 weeks. Percent inhibition of F. sambucinum by single application of mixtures of ASOS and L-menthol or peppermint oil decreased over 11-13 days after treatment, while the mixtures at the same rates consistently inhibited the growth of R. solani for over 15 days. Mixtures of 10 g of ASOS and 4 g or 8 g doses of essential oils were the most effective in inhibiting pathogens growth for periods over 13 or 20 days, respectively. The antifungal effects of essential oils and their components against all tested pathogens suggest their potential use as alternative tools for controlling potato storage diseases.