Occurrence and pathogenicity of crown rot disease organisms in major banana producing Areas in Ashanti Region.

A study was conducted to investigate the occurrence of crown rot disease pathogens in major banana producing areas in the Ashanti Region of Ghana from April to September, 2008. Field survey was conducted in eight districts including Asante Akim South, Asante Akim North Municipality, Ejisu-Juabeng Municipality, Sekyere East, Sekyere South, Mampong Municipality, Kwabre East and Offinso South. Interviews together with semi-structured questionnaires were used in data collection from farmers who were randomly selected from each location. Fifty-six farmers were interviewed from the eight districts. Laboratory work was also conducted at the Plant Pathology Section of the Crops Research Institute (CRI), Fumesua, Kumasi. Crown rot diseased banana samples collected from the eight districts were used for the laboratory study. The survey revealed that 82.1% of farmers practiced mixed cropping farming system with food crops such as cassava, plantain, cocoyam, maize and vegetables including garden eggs, tomato, pepper and okra. Banana suckers from farmers ratoon fields (64.2%) were used in farm establishment. Cultural activities such as weed control (98.2%), mulching (25%), pruning (62.5%) and disease and pests management (23.2%) were practiced. Manual weeding of farm was done three times in a year (53%), dry banana leaves (72.7%) were used in mulching and pruning of dry and diseased banana leaves (100%) were also done. De-budding was practiced in Sekyere South and Offinso South districts. Poor pre- harvest practices such as mulching with diseased banana leaves, no mulching, pruning at the wrong time and the retention of flower bract and male inflorescence were found to influence the occurrence of crown rot disease in the districts. Machete was the main tool used in harvesting mature bunches. After harvest, whole banana bunches (82.7%) were sent to the market. Botryodiplodia theobromae was frequently isolated from Asante Akim South, Asante Akim North Municipality and Offinso South Districts. Fusarium semitectum was isolated from Mampong Municipality and Kwabre East Districts. Colletotrichum gloeosporioides was isolated from Ejisu-Juabeng Municipality, Sekyere East and Sekyere South Districts. B. theobromae, F. semitectum and C. gloeosporioides were the primary pathogens identified to be associated with crown rot disease. These three fungi were able to cause the crown rot disease when inoculated (singly) into healthy banana crowns and in different combinations. C. gloeosporioides alone, B. theobromae + C. gloeosporioides and B. theobromae + C. gloeosporioides + F. semitectum caused a disease severity score of 4 (on a scale of 0-4) in seven days when inoculated into healthy banana crowns. B. theobromae alone, C. gloeosporioides + F. semitectum and B. theobromae + F. semitectum caused a disease severity score of 4 in eight days while F. semitectum caused a disease severity score of 3 (75% infection) in eight days when inoculated into healthy banana crowns. Combination of B. theobromae and C. gloeosporioides recorded the highest rot length of 3.7cm with a disease severity score of 4 eight days after inoculation while B. theobromae inoculated singly had a mean rot length of 2.9cm. However, Aspergillus flavus, Aspergillus niger and Aspergillus terreus were found to be secondary invaders (saprophytes) taking advantage of the disease condition created.

Source: KNUST