The objective of this study was to examine the antifungal activity demonstrated by the Bacillus subtilis isolate B6 against the plant fungal pathogen; Colletotrichum gloeosporioides were isolated from the anthracnose disease in the Lady's Slipper orchid. Filtrated culture medium and non-filtrated culture medium of the B6 inhibited spore germination, and the hyphal growth of C. gloeosporioides. The effect of the B6 non-filtrated culture medium treatment was significantly higher than that of the filtrated culture medium treatment also; it was found that treatment with the 4-day culture medium was significantly more effective than treatment with the 2-day and 6- day culture medium. Additionally, the morphology of the germ tube had changed and had tumed into abnormal shapes. The B6 was developed to two bioproduct formulations namely powder formulation and liquid formulation. The antagonistic bacteria in formulations can survive for more than six months under storage at room temperature. The treatment of the Lady's Slipper leaves by co-inoculation with the formulation 24 hours before the application of the pathogen would clearly serve to reduce anthracnose disease severity as compared to just pathogen inoculation. Therefore, evidently the B. subtilis isolate B6 can be developed for the biocontrol of the anthracnose disease in Lady's Slipper.

Keyword:anthracnose, Bacillus subtilis, biological control, formulation, Lady’s Slipper

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