First record of Cercospora richardiaecola causing leaf spots on Zantedeschia aethiopica in Brazil

Zantedeschia aethiopica (arum lily or local name: copo-de-leite) is an herbaceous member of the family Araceae, that is native to South Africa. In Brazil it is considered among the most important species for the cut flower industry (Lorenzi & Souza, 1995). Little attention has been given to diseases of ornamental plants in Brazil and Mendes et al. (1998) provides no record of fungal diseases of Z. aethiopica in Brazil.

Recently, plants grown both on a flower farm and in a garden nursery in Viçosa (state of Minas Gerais, Brazil) were found to be attacked by a leaf spot disease. The disease was more frequent on older leaves of plants that were grown in the shade and irrigated by spraying. Diseased leaves had circular to irregular greyish-brown necrotic spots, 11-21 mm wide, that frequently coalesced, leading to extensive necrosis of the lamina (Fig. 1). A cercosporoid fungus was found in constant association with the diseased tissues. After examination of the microscopic features of the fungus and direct isolation on V8 juice-agar, the fungus was identified as Cercospora richardiaecola (Chupp, 1954). Conidiophores were mainly hypophyllous, fasciculate, cylindrical, slightly sinuous, geniculate, 74.0-151.0 x 5.0-10.0 µm, dark brown, 3-9 septate; conidia were obclavate to filiform, straight to slightly curved, 40.0-237.0 x 2.5-7.5 µm, 5-15 septate, hyaline, with a thickened and darkened conidial scar (Fig. 2&3). A specimen was deposited at the local herbarium (VIC 26590).

In order to demonstrate pathogenicity, three healthy leaves on each of two arum lily plants were inoculated by using adaxial surface disks, taken from 10-day-old C. richardiaecola cultures grown on V8 agar. After inoculation, plants were left for 48 hours in a moist chamber at room temperature. Typical symptoms of the disease appeared within seven days. C. richaridaecola structures were produced on those lesions. Two non-inoculated plants kept under the same conditions did not develop the disease (Fig. 4).

Cercospora richardiaecola has been previously recorded in the USA, Puerto Rico, Guatemala and South Africa (Chupp, 1954; Farr et al., 1989). This is the first record of this fungus in Brazil and the first time its pathogenicity has been demonstrated.