Occurrence and distribution of Alternaria leaf petiole and stem blight on sweetpotato in Uganda

Assessment of disease occurrence in relation to agroecological and cropping variables is essential for effective Alternaria leaf petiole and stem blight disease control. The occurrence and distribution of the disease was investigated in a systematic survey of the major sweet potato-producing districts in Uganda for two cropping seasons. The composition of the Alternaria sp. was determined from a random sample of diseased leaf tissues. Farmers' practices and perceptions on disease management were also investigated. A survey of the 35 districts in both years showed that Alternaria disease was widespread throughout Uganda. The predominant species observed were A. bataticola (55% of isolates) and A. alternata (40% of isolates). The severity of Alternaria disease was very low, however, the range in disease incidences were from 0 to 49.2%. The disease was more prevalent in the Lake Crescent Region than in the less humid regions of eastern and northern Uganda. No significant correlations were detected between altitude at which sweet potato cultivars were grown and disease severity or yield. Among the sweet potato cultivars surveyed, the lowest incidence of Alternaria disease was detected on cultivars Dimbuca and Silk. The study also noted that perception of farmers and disease practices were contributing factors to disease spread. These studies suggest that selective deployment of cultivars and cultural practices can limit the spread and damage attributed to Alternaria leaf petiole and stem blight disease of sweet potato. This is the first record of A. bataticola on sweet potato in Uganda