Disease surveys carried out between 1989 and 1992 showed Armillaria to be restricted to the northern and eastern parts of Zimbabwe and to be absent from the western and southern parts. Armillaria disease is of local economic significance especially in fruit and clonal pine seed orchards. Pathogenicity studies showed significant differences in infection of cassava (Manihot esculenta) variety Zanaga (Ccv1) between isolates belonging to the three Zimbabwean Armillaria groups (I, II and III), but there were no significant differences in the infection of another cassava variety, Zcv1, from Zimbabwe. The group II isolates failed to cause any infection on the cassava clones. Rhizomorphs were the main means of infection in the pathogenicity studies, although they are rare in nature in Zimbabwe. Results using detached cassava tubers to assess pathogenicity proved to be inconsistent. Periderm restoration responses, which have been observed in woody plants and are presumed to function by restricting pathogen ingress, were observed in cassava infected with Armillaria.