NURSERY AND FIELD EVALUATION OF STREPTOMYCES NIGROGRISEOLUS GANOSA1 TO CONTROL BASAL STEM ROT IN OIL PALM SEEDLINGS

Basal stem rot (BSR) disease caused by Ganoderma species is a threat to the oil palm industry. In our initial study, rhizosphere actinomycetes identified as Streptomyces nigrogriseolus GanoSA1 (Streptomyces GanoSA1) possess competent biological control activity in the growth of Ganoderma in vitro. This study was carried out to evaluate whether Streptomyces GanoSA1 formulated in the vermiculite-bio charcoal powder can reduce disease incidence caused by G. boninense PER71 and promote oil palm growth through nursery and field trial. Mixing of Streptomyces GanoSA1 powder at 108 CFU (colony-forming unit) per gramme in soil resulted in the strain establishment in the applied soil and increased oil palm seedlings height with no observed adverse effect on seedlings growth. The seedlings treated with the powder formulation resulted in a reduced percentage of disease incidence (DI, %) by 51.1 per cent and disease severity index (DSI, %) by 35.0 per cent compared to untreated seedlings and seedlings inoculated with G. boninense PER71 alone (93.3% DI and 75.83 % DSI, respectively). The field trial indicated that, after 36 months of planting, only 6.6 per cent of oil palm treated with the Streptomyces GanoSA1 powder showed symptoms of BSR disease and death due to Ganoderma infection compared to the untreated oil palm at 75.0 per cent. These trials highlight the potential of the Streptomyces GanoSA1 powder to reduce BSR disease in oil palm and promote oil palm growth. Keywords: Streptomyces, Ganoderma, artificial inoculation, seedling baiting technique.