Khalil I. Al-Mughrabi, W.K. Coleman, A. Vikram and R. Poirier
Partner: Potatoes New Brunswick
Abstract: S-carvone, L-menthone, peppermint and spearmint oils were tested in vitro for their inhibitive effects against Fusarium
coeruleum, Fusarium sambucinum, Fusarium avenaceum, Fusarium oxysporum, Alternaria solani, Rhizoctonia solani,
Helminthosporium solani, Phytophthora infestans (A1 and A2 compatibility types), Phytophthora erythroseptica, Phoma exigua and
Pythium ultimum which are causal agents of major potato storage diseases. The growth of the majority of most pathogens was completely inhibited by
the four pure oils tested. Fusarium 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 the oils. 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. Long term inhibitive effects of
mixtures of L-menthol or peppermint oil and aluminum starch octenylsuccinate (ASOS) on the growth of F. sambucinum and R. solani was also tested
in vitro. Growth inhibitions of two pathogens were measured for a period of over 5 weeks and compared with that of different doses of oils
(0.1, 4, 8, 10, and 20 g) mixed with 10 g of ASOS. Percent inhibition of F. sambucinum by single application of the mixtures of ASOS and L-menthol or
peppermint oil decreased over 11-13 days after treatment, while the mixtures at same rates consistently inhibited the growth of R. solani for over 15 days.
Essential oil doses of 4 g/10 g ASOS and 8 g/10 g ASOS were inhibitive for periods of over 13 and 20 days, respectively. Antifungal effects of essential
oils against all tested pathogens suggest their potential to be used as alternative biocides to control potato storage diseases.