Prevalence and Severity of Nattrassia mangiferae Root and Stem Rot Pathogen of Cassava in Bénin.

Root rot pathogens were found through diagnostic surveys in all departments (regions) of Bénin, West Africa, to affect 86 to 100% and 96 to 100% of cassava fields during the dry and rainy seasons, respectively. Disease incidence in individual fields ranged between 0 and 53%, and averaged 16 to 27% per department. Nattrassia mangiferae was consistently the most frequently isolated root rot pathogen (56% in the dry season and 22 to 52% in the rainy season).

First Report of Nattrassia mangiferae Root and Stem Rot of Cassava in West Africa.

During part of the dry season in 1996 (November to December), surveys were made for incidence of root and stem rot in 99 fields of cassava (Manihot esculenta Crantz) randomly selected between latitudes 6°36'N and 7°49'N in Benin (79 fields) and Nigeria (20 fields). Root rot was observed in 65 fields in Benin and 15 fields in Nigeria. Disease incidence ranged from 0 to 54%.

First Report of Curvularia lunata Associated with Stem Disease of Cassava.

During surveys covering 60 cassava (Manihot esculenta Crantz) fields, randomly selected (between latitude 4°55'N and 8°16'N) in south Ghana, and 27 fields in southeast (between 4°50'N and 7°56'N) Nigeria, 8-month-old or older stems of some cassava genotypes were found to be covered by grayish brown lesions, predominantly on lignified portions of stems. Field disease incidence ranged from 0 to 80%, and severity from no disease to highly affected (>15 lesions per stem). To identify the pathogen, infected stem portions were cut out, surface disinfected, and cultured on potato dextrose agar (PDA) acidified with 0.