Welcome to Stellenbosch University

Brief History of Banana Fusarium Wilt

Banana Fusarium wilt was first discovered in Australia by Bancroft in 1874, with reports of disease outbreaks in tropical America following soon thereafter (Costa Rica and Panama in 1890). Because of its early discovery in Panama, the damage it caused to plantations in the country and the unknown nature of its cause, the disease became popularly known as Panama disease. The disease-causing agent was isolated by Dr Erwin Smith after inspecting a Cuban sample in 1910, and the responsible fungus named Fusarium cubense. But it was E.W. Brandes who first demonstrated its pathogenicity to banana when he inoculated bananas in steam-sterilised soil infested with the fungus. Panama disease did not attract much further research attention until a severe epidemic broke out in tropical America subsequent to the establishment of vast monoculture plantations of the highly prized 'Gros Michel' banana for export. Three decades after its isolation the pathogen was recognized to be a variant of the ubiquitous F. oxysporum species, and was renamed F. oxysporum f. sp. cubense (Foc).

It is believed that the movement of Foc has been closely linked to the dissemination of susceptible clones into Australia, the Americas and Africa, since the pathogen is often introduced into new areas on infected rhizomes that are free of visual symptoms. The fungus might have been introduced into the West Indies with the Silk variety that came from South India, and from there spread to Central and South America during the time when Gros Michel was widely planted for export in the area. Between 1926 and 1959 the export trade in Central and South America was well established and successful, but suffered huge losses due to the rapid spread of Foc and the susceptibility of Gros Michel. Gros Michel was eventually replaced with resistant Cavendish cultivars during the 1960s. Cavendish cultivars, though, were found to be susceptible to Foc in the subtropics. They first succumbed to the disease in the Canary Islands in the 1920s, followed by reports of banana Fusarium wilt in South Africa (1940s), Australia (1950s) and Taiwan (1970s). A devastating strain of Foc was discovered in Cavendish plantations in Indonesia and Malaysia in 1990. This strain, called Foc TR4, spread to northern Australia in 1997, and was thereafter reported from Taiwan, the Philippines and mainland China. After being confined to Asia for almost two decades, Foc TR4 has spread to the Middle East and Mozambique.

Based on pathogenicity to different banana cultivars, three races of Foc have been recognized. Race 1 causes disease in the Gros Michel (AAA) and Silk (AAB) cultivars. Race 2 attacks Bluggoe (ABB), and race 4 infects Cavendish (AAA) cultivars and all the cultivars that are susceptible to Foc races 1 and 2. Foc race 4 is further subdivided into tropical and subtropical strains, the former attacking Cavendish banana in the tropics while the latter attacks Cavendish bananas grown in the subtropics, where cold winters are thought to predispose these cultivars to infection. Race 3 has been omitted as a pathogen of banana, as it only attacks Heliconia spp.  All evidence on the genetic diversity and ancestry of Foc points towards an Asian origin for the banana pathogen, as most isolates of the pathogen from outside Asia are related to the Asian population. However, independent evolution could also have occurred outside this centre of origin, with a variant of the fungus isolated from a specific geographical area in Malawi being genetically distinct from other isolates of Foc.

Fusarium wilt can be found in all banana-producing countries of the world except the South-Pacific islands, parts of Melanesia, and countries around the Mediterranean Sea and Somalia. Most recently the disease was reported from New Guinea and Yap in the Federated States of Micronesia. Once the fungus is introduced into a disease-free plantation, it can spread with contaminated irrigation water and soil attached to implements, shoes and vehicles. Heavy rainfall can lead to increased spread of the pathogen from plant to plant and from the surface down to the roots. The run-off water may contaminate the irrigation reservoirs and increase the spread of the fungus through the plantation.

Since the discovery of Fusarium wilt of banana, various control methods have been attempted to curb the damage caused by the disease. Yet, no long-term control measures are available other than the planting of resistant cultivars. Soil fumigation, fungicides, crop rotation, flood-fallowing and organic amendments are some of the control strategies that have been investigated in the past. Studies on biological control and soils that are naturally suppressive to Fusarium wilt of banana due to beneficial microorganisms have yielded unconvincing results. Many effective biological control agents can be found for Fusarium wilt diseases of other crops, which make biological control a promising option for the integrated management of Fusarium wilt of banana. Current practices for the prevention of Fusarium wilt of banana include the use of disease-free tissue culture plantlets and proper sanitation methods. The treatment of vehicles, machinery, tools and footwear with effective surface disinfectants is particularly important. In fields where Foc is already present, the planting of resistant cultivars is essential, if such cultivars are acceptable to the local markets.