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Disease Note

Lemongrass Rust Caused by Puccinia nakanishikii in Hawaii. D. E. Gardner, National Park Service CPSU, Department of Botany, University of Hawaii, Honolulu 96822. Plant Dis. 69:1100. Accepted for publication 6 August 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-1100a.

Lemongrass (Cymbopogon citratus (DC.) Stapf), native to the East Indies, is cultivated in Hawaii for its lemonlike fragrance and for making tea. A rust fungus, identified as Puccinia nakanishikii Diet., was observed on lemongrass at Pearly City and Manoa Valley on the island of Oahu in 1984 and 1985. This is the first report of this rust in Hawaii. Mildly to moderately infected leaves show discrete linear, cinnamon-brown uredinia on the abaxial surfaces associated with chlorotic streaks, whereas severe infection causes extensive necrosis corresponding with coalesced uredinia. Telia also occur on severely infected leaves. No aecial host is known for this pathogen. Telial and uredinial characteristics, including the presence and distinctive morphology of paraphyses, distinguish P. nakanishikii from other rust fungi reported to attack Cymbopogon spp. elsewhere. Two of these fungi, P. purpurea Cke. and P. versicolor Diet. & Holw., occur in Hawaii on closely related hosts, such as sorghum, but have not been observed on lemongrass.