Studies on the etiology and symptomatology of root and storage rot disease of cocoyam in Nigeria.

The losses caused by root and storage rot of cocoyam in Nigeria are estimated as 40 to 45%. Field symptoms of the disease include inhibited growth, leaf chlorosis followed by necrosis and shrivelling of affected parts, and finally premature death of the aerial portions of the plant. A large proportion of the roots are destroyed. Poor production of cormels and reduced corm size are other field symptoms of the disease, differing according to the type of causal agent. Botryodiplodia theobromae, Fusarium solani, F. moniliforme, and Sclerotium rolfsii were isolated from diseased corms, occurring single or in mixed infection. All isolated fungi proved pathogenous on Xantbosoma spec. as well as on Colocasia spec., with Colocasia exhibiting greater damages. Three types of rot are suggested for classification of cocoyam rot in Nigeria: black rot, Fusarium rot, Sclerotium rot.