Stem and foliar blight in roselle (Hibiscus sabdariffa L. var. sabdariffa)in the tropical forest region of south-western Nigeria

The aetiology and epidemiology of leaf and stem blights of roselle (Hibiscu s sabdariffa L. var. sabdariffa) was investigated at Ibadan, in the tropica l forest region of south-west Nigeria. Out of 250 diseased plants examined, 63% had symptoms of leaf blight, 46% stem blight and 42% had both. Leaf bl ight symptoms were associated with infection by Phyllosticta hibiscini and stem blight with Fusarium oxysporum. Infection in the field by these fungi occurs during the peak of the rainy season, beginning in patches which late r spread, causing extensive blight, defoliation and complete wilting. Popul ations of 4.6 +/- 0.5 x 10(6) g(-1) and 4.3 +/- 0.4 x 106 g(-1) colony form ing units/g were found in soil for P. hibiscini and F. oxysporum respective ly, while plant debris also harboured both pathogens.