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Ramorum Leaf Blight and Sudden Oak Death, caused by the pathogenic oomycete Phytophthora ramorum, have brought an uncertainty to the future of western forests. Two understory hardwoods, tanoak (Notholithocarpus densiflorus (Hook. and Arn.) Manos, C.H. Cannon, and S. Oh) and California bay (Umbellularia californica (Hook. & Arn.) Nutt.), are commonly infected with Ramorum Leaf Blight, the foliar form of the pathogen. As the lethal Sudden Oak Death is the form of this pathogen most commonly studied, comparatively little research has been conducted on the non-lethal Ramorum Leaf Blight. This study therefore measured physiological characteristics (midday water potential, stomatal conductance, net photosynthesis, and water-use efficiency) of healthy and infected foliage from tanoak and California bay trees in Redwood National Park to determine the effects of the blight on leaf-level productivity. For both species, midday water potential, stomatal conductance, and net photosynthesis were all lower in infected samples compared to healthy samples. There was no significant difference in water-use efficiency between infected and healthy foliage. Results suggest that Ramorum Leaf Blight can lower leaf-level productivity. Further research on the subject is still needed to better support informed management decisions in infected forests and to predict the long-term effects of the foliar blight, a pathogen with hundreds of host species, in the Pacific Northwest.