The hyphomycete genera Exochalara and Monilochaetes

The fungus Monilochaetes infuscans causes scurf disease or soil stain of sw eet-potato, Ipomoea batatas. The disease was known from America since 1890, later also from Australia, Asia, Europe, New Zealand, and the Pacific Isla nds; in South Africa it was reported in 1995. Comparative morphological and cultural investigations of M. infuscans, the type species of the genus, an d species of the related genera Exochalara and Dischloridium indicated that D. cylindrospermum is conspecific and E. guadalcanalensis congeneric with M; infuscans. The new combination M. guadalcanalensis is proposed. This arr angement results in Monilochaetes accommodating two species, while the type species of Exochalara, E. longissima (Grove) W. Gams & Hol.-Jech., and a s ubsequently described species, E. imbricata Hol.-Jech., are retained in Exo chalara, a genus characterized by sympodially branching, rather pale brown, concolorous conidiophores and rather narrow, fusiform conidia. The type sp ecies of Dischloridium, D. laeense, is quite distinct in having strongly fa sciculate conidiophores and much larger conidiogenous dimensions, but other species described in that genus may also be assigned to Monilochaetes, but the generic limites are not yet sufficiently defined.