EFFICACY OF PLANT EXTRACT FORMULATIONS TO SUPPRESS STEM ROT DISEASE ON VANILLA SEEDLINGS

Four plant species, i.e. Eugenia aromatica (Family Myrtaceae), Piper betle (Family Piperaceae), Alpinia galanga (Family Zingiberaceae) and Sphaeranthus indicus (Family Compositae) were used to develop extract formulations to confirm their antifungal activity. Of the six formulations tested, four formulation, F1,F2,F3 and F4, contained each extract of above mentioned plants, while F5 and F6 were consisted of the mixtures of E.aromatica and P.betle extract and A.galanga and P.betle extract, respectively. Treatment with 5% solution of F5 formulation showed the highest inhibitory effect against the radial growth of F. oxysporum f.sp. vanillae on PDA medium. Diameter of 5 days fungal colony on PDA treated with F5 was only 6.7 mm, while 87.9 mm on the non amended control. The development of stem rot disease was obviously suppressed on vanilla seedlings grown in the soil treated with 5% solution of each plant extract. The lowest disease incidence was attained by the treatment of F5, in which only 7% of the vanilla seedlings were infected. The low disease incidence in the plot treated with F5 was in line with the low population density of F. oxysporum f.sp. vanillae in the soil. Results of present study displayed that an extract formulation containing the mixture of E. aromatica and P. betle extracts was the most effective treatment to suppress the population growth of F. oxysporum f.sp. vanillae in the soil and in turn to suppress the stem rot disease on vanilla seedlings. This formulation can be used as an alternative measure to control stem rot disease on vanilla seedlings preparation.