Podosphaera macularis displays phenotypic variation on cultivars with major R-gene and partial resistance when a given form of host resistance is broadly deployed in the landscape. As of 2020, the hop cultivar ‘HBC 394’, trademarked name Citra®, was the most widely planted hop cultivar in the U.S. We characterized the pathogenic diversity of isolates of P. macularis on Citra® and determine whether isolates with local or general adaption have emerged coincident with shifts of Citra® to be the most widely planted cultivar. Among 27 isolates from Citra®, all were able to infect differential cultivars possessing the R-genes Rb, R3, and R5; nine isolates were additionally virulent on the differentials for R4 and R6. A collection of 92 other isolates from Citra® found that 98.9% lacked R6-virulence. Inoculations of seven isolates of P. macularis with complex virulences onto detached leaves of Citra® all produced disease, indicating a known major R-gene does not predict the powdery mildew phenotype in Citra®. Citra®-derived isolates and isolates representing the three predominant pathogenic races of P. macularis found in the Pacific Northwest had no major difference in aggressiveness when inoculated on Citra®. Citra®-derived isolates caused similar levels of disease on a range of hop cultivars as isolates derived from other hop cultivars. These findings adduce that the P. macularis isolates found on Citra® may have varied phenotypes. However, at this time, these isolates display neither a local adaptation for increased virulence on Citra® or a general adaptation for enhanced virulence across cultivars.