The probe hybridized with all 34 strains of P. s. phaseolicola tested. All interspecific (pathovar) or intergeneric hybridizations were negative. Hybridization tests were highly reliable for pathogen detection and identification when individual colonies of P. s. phaseolicola could be picked individually from seed-soak liquid assay plates or when maceration fluids from disease lesions were assayed. Probings of maceration fluids from disease lesions also were highly reliable. In contrast, soak liquids from seeds contaminated with P. s. phaseolicola or washings of colonies from agar plates of such liquids gave variable results