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Disease Note

Occurrence of Canna Rust (Puccinia thaliae) in Hawaii. D. E. Gardner, National Park Service CPSU, Department of Botany, and A. P. Martinez, Department of Plant Pathology, University of Hawaii, Honolulu 96822.  Plant Disease 69:1101, 1985.  Accepted for publication 6 September 1985.  Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-1101e.

Members of the genus Canna are widely grown in Hawaii as ornamentals.  These plants are commonly attacked by Puccinia thaliae Diet. (= P. cannae (Wint.) P. Henn.) throughout Hawaii.  Infection is conspicuous and widespread on C. indica L. and its horticultural derivatives.  Small, discrete uredinia occur abaxially or on both surfaces of mildly infected upper leaves and leaf sheaths, with corresponding necrotic spots on the opposite side.  Middle and lower leaves are frequently severely infected and are covered with coalesced yellow uredinia, resulting in chlorosis and death of leaves and, often, decline of the entire plant.  Telia are dark, subepidermal, and either scattered or surrounding groups of uredinia in small, more or less concentric rings.  Size and morphology of urediniospores and teliospores from Hawaii correspond to those of the published description of this fungus.  Pycnia and aecia have not been described for P. thaliae.  Canna rust has been reported several times since the early 1970s, according to University of Hawaii Plant Disease Clinic records, but presence of this potentially devastating disease in Hawaii has not been previously published.