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How is Fusarium oxysporum spread?
Fusarium oxysporum is an asexual fungus that produces three types of spores: microconidia, macroconidia, and chlamydospores. Microconidia are one or two celled, are produced by Fusarium oxysporum under all conditions, and produced the most within the infected plants. Macroconidia are three to five celled and are commonly found on the surface of plants that have been killed by Fusarium wilt. Chlamydospores are the third type of spore and are either one or two celled. Chlamydospores can remain dormant in soil and infect other hosts for as long as 30 years, and all of these spores can spread through running water, on farm implements and machinery. (

F. oxysporum spores have also been proven to live on non-host plants in the absence of a susceptible host. This provides a means of survival for the fungus, which remains virulent until a host plant appears. When non-host plants become infected they show few, if any symptoms, and become a carrier of the pathogen. A study by Waite and Dunlap (1953) showed that, on a farm devastated by Fusarium wilt, there were traces of F. oxysporum in three common types of grass, a low growing herb and the roots of common weeds. (Fungal Wilt Disease of Plants, Mace)

Underground rhizomes are often another means of spreading the disease. Bananas raised for human consumption do not produce seeds. So, rhizomes are used as "planting material to establish new banana plantations." ( When a banana plant is infected with Fusarium wilt, the rhizome usually doesn't show any symptoms, but if the infected rhizome is used to grow new bananas, the crop will always die of Fusarium wilt before the fruit matures. (

Unfortunately, for many planters, once Fusarium oxysporum is established in soil it may be incredibly tough to eradicate. Chlamydospores can remain dormant and infect the soil for many years. "The only effective response is soil sterilization, which is far too expensive for most farmers." ( Fungicides have limited results as well, but use of resistant crops is the most common answer.

Cavendish banana cultivars are a wilt-resistant, widely used breed. When they were introduced in the 1960s to replace Gros Michel bananas, they "saved the international banana export trade inductry". By the time they were replaced, Fusarium wilt had destoryed almost 40,000 ha in Central America. Though the Cavendish cultivar is still relatively wilt-resisitant, in the 1970s, almost one third of the total population of bananas in Kiepersol, South Africa were destoryed by Fusarium oxysporum. "Fortunately, the disease has not been discovered in the other three banana production areas Levubu, Letaba, and the Underberg", so many banana breeding areas such as the Caribbean and Latin America are substituting wilt-resistant Cavendish clones into the Gros Michel production. (

Though some Cavendish clones have remained resistant to F. oxysporum, plant breeders and scientists continue to develop new resistant cultivars. Sadly, the development process is very slow. Bananas grown for commerical use are seedless and reproduce asexually, which makes breeding difficult and decreases genetic variation. (
For more information on treatment for Fusarium oxysporum and resistant banana plants:

Fusarium Wilt May be Controlled by Other Fusarium Strains (For Tomato)
Vegetative compatibility groups within Australian populations of Fusarium oxysporum f. sp. cubense, the cause of Fusarium wilt of bananas
2nd International symposium on fusarium wilt
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