Canna indica L., known as Indian shot or canna lily, occurs throughout the New World in tropical and subtropical areas. This upright, perennial, rhizomatous herb is a popular garden plant in South Africa because of its spectacular plant habit and growth vigor. During January 2005, canna lily leaves with rust symptoms were collected from Pietermaritzburg in the province of KwaZulu-Natal. Orange-yellow uredinia were observed primarily on the abaxial surfaces, often covering the entire leaf with coalescing pustules. Koch's postulates were completed in repeated tests with spray inoculations of blooming potted plants, urediniospores suspended in water (42 × 104 spores/ml), incubation in a dew chamber for 14 h at 20°C in the dark, and then returned to the greenhouse. Symptoms similar to those of the original collection formed 10 days postinoculation. Only the uredinial stage was observed, which was characterized by hypophyllous, yellow-brown, subepidermal, erumpent, and irregular shaped uredinia. The urediniospores were round to ovoid, orange-yellow, echinulate, and 25 to 35 × 15 to 20 μm. The pathogen was identified as Puccinia thaliae Diet. according to its description on Canna edulis Ker-Gawl. (1). Following the report of P. thaliae on C. indica in Hawaii in 1989 (2), to our knowledge, this is the first description of canna lily rust in South Africa.
References: (1) M. L. Jeeva et al. Plant Pathol. 53:261, 2004. (2) D. E. Gardner and C. S. Hodges. Pac. Sci. 43:4155, 1989.
