Technical Abstract: Pseudomonas cannabina pv. alisalensis (Pca) causes bacterial blight on crucifers, which can reduce crucifer yields and result in economic losses in the US. Prior to the late 1990s Pca was not distinguished from the pepper spot pathogen of crucifers, Pseudomonas syringae pv. maculicola (Psm), although they have since been found to have distinct host ranges and belong to different species. The objective of this research was to determine whether recent and historical reports of crucifer diseases attributed to Psm were in fact caused by Pca. Bacteria identified as Psm from disease outbreaks worldwide were compared to Psm and Pca. DNA fragment banding patterns generated by repetitive-PCR using the Box A1R primer distinguished Pca from Psm and demonstrated that some of the pathogens previously identified as Psm were Pca. Additionally, the putative Pca strains and the pathotype of Pca were sensitive to bacteriophage PBS1 while Psm was not. The identity of the putative Pca strains was confirmed through host range evaluations. The putative Pca strains and the Pca pathotype were pathogenic on radish (cv Comet), rapini (cv Sorrento) and oats (cv Montezuma) but Psm was not. Correctly identifying and distinguishing these pathogens is crucial for developing effective management strategies and preventing pathogen spread. The outlined suite of assays represent methods effective in distinguishing these previously commingled pathogens.