Authors
J. E.
Smith
,
Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, 0002, South Africa
, and
T. A. S.
Aveling
,
Department of Botany, University of Pretoria, Pretoria, 0002, South Africa
During surveys of cowpea (Vigna unguiculata (L.) Walp.) fields in the Gauteng province, a destructive stem disease was observed. Stem symptoms began as tan brown discolorations that later spread, becoming dark purplish-brown. Sunken, necrotic lesions and small, black acervuli also were visible on the stems. Colletotrichum dematium (Pers.) Grove was consistently isolated from diseased material. Pathogenicity of an isolate of C. dematium from cowpea stems (deposited with the National Collection of Fungi, South Africa, designated PPRI 6121) was confirmed by inoculating stems of 20 cowpea seedlings with a 105 conidia per ml suspension. Inoculated plants were maintained in humidity chambers for 48 h and then returned to the greenhouse. After 7 days, symptoms resembling those observed in the field were apparent. C. dematium was reisolated from these plants and produced cultures identical to those of the original isolate. This is the first report of C. dematium on cowpea in South Africa.
