A fruit quality problem has been identified in far north Queensland during the processing of ripe banana for pulp. The disease symptoms show an internal fruit discoloration; reddish brown to blackish centre and pulp breakdown. The incidence of disease has been estimated at 1% of ripened fruit and it is found most common in wet season. Initially it was thought to be a physiological problem, but two bacteria from the Enterobacteraceae family; Pantoea agglomerans and Enterobacter cowanii have been frequently recovered from infected fruits. Artificial inoculations of banana fruit with the bacteria were conducted at the QDAF South Johnstone Research Station to determine their pathogenic nature. Fingers on bunches at the bract-lift stage were injected with suspensions (10 8 cfu /ml) of each of the bacteria. One month after inoculation, fingers were cut open to check for disease development. Both bacteria produced similar symptoms to the fruit samples taken from the pulp processing facility. Inoculated fingers were easily distinguished from others in the bunch by their deformed shape, being out of line with other fingers and their premature
yellowing and reduced fruit size. Internally, inoculated fingers showed a rusty red discoloration of the pulp with a deep gelatinous cavity. The exact disease cycle caused by these opportunistic bacteria is currently unknown. No treatment has been identified to manage the bacteria, the risk of infection may be reduced through insect pest management and maintaining the proper drainage and field sanitation during warm and humid weather conditions. Fruit with obvious symptoms of deformity (narrow at flower end or straight and out of alignment) should be discarded at the packing shed.
This study provided the first report of Enterobacter cowanii and Pantoea agglomerans causing internal finger rot or fingertip rot of banana.