Chemical Control of Two Leaf Spot Diseases of Cluster Yam (Dioscorea dumetorum) Caused by Cercospora contraria and Didymosphaeria donacina. S. A. Emua, Department of Botany, University of Ibadan, Ibadan, Nigeria. A. O. Fajola, Department of Botany, University of Ibadan, Ibadan, Nigeria. Plant Dis. 67:389-391. Accepted for publication 28 July 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-389.

Five fungicides (captan, basic copper chloride, captafol, mancozeb, and Phaltan) were evaluated for inhibition of germination of the conidia of Cercospora contraria and Didymosphaeria donacina, which cause two leaf spot diseases of Dioscorea dumetorum. The fungicides were also evaluated after artificial infection in the greenhouse and natural infection in the field during two growing seasons. Four of the fungicides (captan, captafol, mancozeb, and Phaltan) were consistently effective in inhibiting germination of the conidia in the laboratory and inhibiting the diseases in the greenhouse and in the field. Mancozeb, however, has been recommended for field use because of its effectiveness, low phytotoxicity, low cost, and the apparent luxuriant growth it induced in treated plants.