Fusarium Tropical Race 4 (TR4)

Fusarium of banana is a disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense­.

The different strains of the fungus (around 35 different reported so far) are grouped into four main ‘races’ based on their vegetative compatibility. Races one, two and three affect relatively small number of banana cultivars. Race four can infect most varieties, but is known predominantly for attacking Cavendish, the most widely cultivated variety in the world. Race four of Fusarium oxysporum f. sp. cubense is further categorised in two groups:

  • Subtropical race four (STR4), causing disease in the presence of predisposing factors such as low temperatures;
  • Tropical race four (TR4), causing disease without predisposing factors. If unchecked, Fusarium caused by Foc TR4 can wipe out an entire plantation. The pathogen can be transmitted through planting materials, movement of infested soil particles through any means such as shoes, vehicles or through water. The fungus is able to remain dormant in the soil for decades. For these reasons, Foc TR4 is considered as the world’s greatest threat to banana production.

Fusarium of banana – infection and symptoms

Fusarium oxysporum f. sp. cubense spores can lie dormant in the soil until a susceptible banana plant is established nearby. The spores infect the plant through the roots and colonise the plant’s xylem vessels, blocking the flow of water and nutrients. This condition produces the symptoms called Fusarium. The characteristic symptom of Fusarium is blackened, discoloured and weakened vascular tissue within the stems of the plant. The discolouration varies from pale yellow in the early stages to dark red and black in the later stages. Internal symptoms initially develop in the feeder roots and rhizomes and then in the plant’s pseudostem.

Externally, the first signs of the disease are wilted plants with yellowing older leaves around the margins. Sometimes the leaves remain green longer on the petiole, but as the disease progresses they eventually collapse forming a ‘skirt’ around the pseudostem before falling off. New leaves may have irregular, pale margins and wrinkled blades.

The disease may cause the pseudostem to wilt or collapse. Infected suckers (used for seeding new plants) and rhizomes do not start showing symptoms of the infection until they are around four months old. Therefore, the fungus can easily spread also through infected suckers which may be symptomless. Fruit shows no symptoms of disease.


  • The fungus can remain dormant in the soil for more than 30 years. They are resistant to fungicides and cannot be eliminated from the soil by any chemical treatment.
  • Spores can be carried on clothing, equipment or the soles of shoes. People, vehicles and animals can spread the fungus through moving infested soil particles.
  • Suckers and rhizomes originating from infected plants will be asymptomatic for up to four months, but will then develop Fusarium.
  • Spores can be carried in irrigation water or surface run-off water. They can also contaminate irrigation reservoirs. Flooding has a big role in spread the fungus.


Fusarium TR4 has infested banana plantations in South-East Asia and Pakistan, and has more recently been reported in Jordan, Mozambique and Australia. It is a growing concern for the industry as it colonizes, infects and destroys Cavendish banana plants. Once present, the disease can't be controlled by common chemical or cultural management practices. Available methods for disease containment are not fully efficient on TR4; and alternative options are still at the evaluation stage. The social consequences of Fusarium can be severe: bananas are an important source of food, income, employment and government revenues in many tropical countries.

Bananas (Musa spp.), including dessert banana, plantain, and cooking banana, are the eighth most important food crop in the world, and the fourth most important in the least developed countries (FAOSTAT, 2015). They are produced in 135 countries and territories across the tropics and subtropics. The vast majority of producers are smallholder farmers who grow the crop for either home consumption or local markets (less than 15% of the global production of more than 130 million metric tonnes is exported). Today, the international banana export trade is worth some US$ 10 billion per year (FAOSTAT).

Virtually all export bananas, and also a considerable part of the bananas cultivated for own consumption or local markets are Cavendish bananas or other cultivars susceptible to Fusarium TR4.

In brief, Fusarium TR4 has the following profile:

  • There is no viable fully effective treatment of soil or plants to control or cure Fusarium in the field;
  • The fungus’ resting spores remain viable in the soil for decades;
  • Research is going on; however, the biology and genetics of the fungus are still not fully understood;
  • There are no resistent varieties yet that can replace the export Cavendish banana;
  • The only currently available preventive measure is quarantine: preventing the transfer of infected soil or plant material from infected areas to TR4-free areas.
Source: fusariumwilt.org