First Report of Cladosporium colocasiae on Taro in the United States. G. E. Holcomb, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. . Plant Dis. 73:938. Accepted for publication 18 July 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0938C.
Cladosporium colocasiae Sawada has been identified in Louisiana
on Colocasia esculenta (L.) Schott (taro, elephant's-ear), a plant widely
used for shoreline plantings and now naturalized in Louisiana and
other southern states. The fungus causes initially olivaceous leaf spots
that become tan to brown and necrotic with age. Spots are 5-10 mm
in diameter, irregularly round to oval, and frequently surrounded by
a chlorotic halo. They often coalesce to form large necrotic areas.
The fungus sporulates on both surfaces of lesions. This disease is
most common during the fall months and has been observed in Baton
Rouge since 1970. Pathogenicity tests were performed with pure
cultures of the fungus, isolated on potato-dextrose agar, by misting conidial suspensions in distilled water on healthy taro leaves. Typical
lesions developed 7-10 days after inoculation, and C. colocasiae was
reisolated. The disease occurs worldwide on taro in tropical areas,
including Hawaii, and is reported here for the first time in the
continental United States (1).