Native rhizobacteria as biocontrol agents of Heterobasidion annosum s.s. and Armillaria mellea infection of Pinus radiata

• Native Pinus radiata rhizobacteria inhibit growth of fungal pathogens H. annosum and A. mellea.
• P. fluorescens S32R2 and E. billingiae S31R1 were strong antagonists of both fungi in vitro.
• P. fluorescens S32R2 and B. simplex S11R41 best protected P. radiata seedlings against both fungi.

Biocontrol bacteria Pseudomonas fluorescens, Bacillus simplex and two different strains of Erwinia billingiae were isolated from the rhizosphere of a healthy tree located in a Pinus radiata plantation with high presence of fungal pathogens. The bacteria were selected based on a high level of antagonism in vitro against P. radiata pathogens Heterobasidion annosum s.s. (68.6–99.3% area inhibition percent (AIP)) and Armillaria mellea (64.8%–94.2% AIP). None of the bacteria were pathogenic for two-month-old seedlings of P. radiata. P. fluorescens and B. simplex reduced the incidence of H. annosum and A. mellea infection on P. radiata. While H. annosum was detected in 90% of seedlings that were not inoculated with bacteria, detection was reduced to 40% and 55% of seedlings treated with P. fluorescens and B. simplex, respectively. Following infection with A. mellea, 54% of the seedlings that were not treated with bacteria died, whereas for those treated with P. fluorescens, B. simplex and the two strains of E. billingiae, the proportion of plants that died was 13.1%, 7.1%, 3.6% and 11.6% respectively.