Colonisation of apple and pear leaves by different strains of biological control agents of fire blight

The ability of biological control agents of fire blight to establish and colonise the surface of apple and pear leaves was investigated Two commercially available biological control agents Pantoea agglomerans P10c and Pseudomonas fluorescens A506 and two strains of P agglomerans isolated from apple orchards in New Zealand were used All of these strains are able to reduce fire blight incidence on apple and pear flowers After spray application the percentage of leaf surface colonised by the biological control agents was measured by imprinting leaves on fresh agar plates Pseudomonas fluorescens A506 did not survive for more than two days in the field while the strains of P agglomerans survived for several days but the percentage of leaf area colonised decreased rapidly after 48 hours These strains might not have the characteristics necessary to control fire blight infections on shoots