Prevalence of Cassava Root Disease in the Brong Ahafo Region of Ghana

Abstract

Cassava root rot diseases contribute to substantial yield loss in cassava production. The study determined the incidence and severity of the cassava root rot disease in the Forest and Transition zones of the Brong-Ahafo Region; identified the disease pathogen; assessed farmers’ knowledge on the disease and identified cultural practices that promote the disease. Six focus group discussions and a survey was carried out with 55 cassava farmers in the Dormaa East and Sunyani West Districts (Forest zone) and Nkoranza South Municipal (Transition zone) and their farms were sampled for rotten roots and laboratory investigations carried out.  The highest mean disease incidence recorded at Amanfe (34.7%) was similar to that at Wamfie (31.4%); Kwatire (31.2%); Kyeremasu (31.0%); Merefrewo (30.8%); Nsoatre (27.2%); Kwasoa (24.6%); Asuakwaa (21.0%) in the Forest zone. However, the mean incidence of the disease at Amanfe was significantly higher than that recorded at Wagadudu (17%); Sessima (12%); Akuropong (4%) and Asempanaye (8.1%) in the Transition zone. The highest mean severity score of 4 was recorded at Wamfie was not significantly different from that recorded at Amanfe (3); Kyeremaso (3); Merefrewo (3); Asuokwaa (3); Nsoatre (2) Kwaasoa (2) and Kwatire (2) in the  Forest zone. However it was significantly higher than that at Sessima (1); Akuropong (0.5) and Asemapanaye (0.5) in the Transition zone. Mean disease incidence and mean severity of the cassava root rot disease is higher in the Forest than in the Transition zone. Lasiodiplodia theobromae was frequently isolated from the diseased samples. All the respondents were aware of the disease. Delayed harvesting; planting in waterlogged soils and high weed density were reported as the causes of the cassava root rot disease by 71%, 25.5% and 3.6% of the respondents.  More than 70% had cultivated cassava continuously for at least three years; only 9.1% intercropped cassava with groundnut to improve soil fertility; none applied chemical fertilizer; and all the respondents retained mature roots in the ground for prolong periods. The farmers have a fair knowledge of the cassava root rot disease but they lack methods to control the disease. Unfavourable environmental conditions and poor farm management practices contribute to cassava root rot disease.