Technical Abstract: Since 2002, severe leaf spotting on parsley (Petroselinum crispum L.) has occurred in Monterey County, California. One of two different pathovars of Pseudomonas syringae sensu lato were isolated from diseased leaves from seven distinct outbreaks and twice from the same outbreak (2002 and 2009). Fragment analysis of DNA amplified between repetitive sequences (rep-PCR), 16S rDNA sequence analysis, biochemical and physiological tests identified the pathogens as Pseudomonas syringae pv. apii and P. syringae pv. corriandricola. Koch’s postulates and host range tests demonstrated that Pseudomonas syringae pv. apii and P. syringae pv. corriandricola cause leaf spot diseases on parsley, celery and coriander. A phylogenetic tree was built based on the concatenated sequences of the four housekeeping gene fragments gap1, gltA, rpoD, and gyrB for one hundred and eighty-nine strains of Pseudomonas syringae including over 40 pathotype strains and sequences were uploaded to the Plant-Associated Microbes Database (PAMDB). The topology of the phylogenetic tree generated by MLSA directly corresponded to P. syringae genomospecies and P. syringae pv. apii was allocated appropriately to genomospecies 3. This is the first demonstration that MLSA can accurately allocate members new pathogens directly to Pseudomonas syringae sensu lato genomospecies. According to the MLSA P. syringae pv. coriandricola is a member of genomospecies 9, P. cannabina. In a blind test both P. syringae pv. coriandricola and P. syringae pv. apii isolates from parsley were correctly identified to the pathovar. In both cases MLSA described diversity within each pathovar that was previously unknown.