TR 4 fungus: Does good soil protect organic bananas?

The banana plant disease TR 4, which has destroyed large banana stocks in Asia, arrived in Colombia. Four plantations are affected so far, including one organic plantation. The hypermarket chain real, which has converted its banana assortment to organic, is already rejoicing that they are not affected due to the good soil of their organic banana plantations. For BanaFair Manager Rudi Pfeifer, this reasoning is unfounded.

Is it clever marketing or due to the fact that CEO of real Patrick Müller-Sarmiento has Colombian roots? When it became known that banana plantations in the Latin American state were affected by the dangerous fungal disease Tropical Race 4 (short: TR 4), the hypermarket chain quickly pointed out that their organic bananas were not affected, saying that real organic bananas defy TR 4.

Healthy, humus-rich soil as protection?

The reasoning sounds logical. Peter Reitz, Head of Fruit and Vegetable Purchase at real explained that the fungus forms in soil that is heavily leached out by decades of monoculture and pesticide usage. He said that these so would not longer contain any microorganisms, resulting in unhindered spreading of the fungus. According to him, the organic or Demeter-certified bananas offered at real are exclusively grown on plantations with healthy, humus-rich soils, so the fungus has no chance. Therefore, although real bananas mostly come from Colombia and are the variety Cavendish, they should not be affected by the outbreak.

Organic banana plantation also affected

The banana variety Cavendish is cultivated both conventionally and organically. It was introduced as an export banana after the TR 1-fungus destroyed the stocks of the variety Gros Michel, previously main export banana, in the 1960s. It is not known whether organic bananas survived the disease at the time. According to Rudi Pfeifer, Managing Director of BanaFair, TR 4 already affects an organic banana plantation (see interview below). However, with a size of 90 hectares, this is an organic monoculture of the Dole Food Company. Whether smaller organic plantations with organically grown soils are resistant to the fungus remains to be seen.

Field trial with organic fertilizer

An experiment by scientists gives little hope: in a contaminated cultivation site in Southern China, they observed soil enriched with bio-organic fertilizer and untreated, anaerobically disinfected soil for comparison. The results showed that bio-organic fertilizer was able to reduce the amount of TR 4 in the soil, but the suppressive effect on the fungus decreased after one month. After two months, there was no significant difference between the treated and the control soil. While the fungus population then decreased in all environments, it increased again in the sixth growth month of the freshly planted banana plants.

The exact structure and procedure of the field trial can be found in the study “Temporal variations of Fusarium oxysporum f. sp. Cubence tropical race 4 population in a heavily infected banana field in Southwest China”.

Protective power of soils ineffective in monocultures?

Even after this experiment it remains open whether a bio-organically grown soil is effective against the fungus. As a sceptical phytomedicine expert put it: Even a vital persona who eats healthily and keeps fit through sport can get nail fungus. With this, he indirectly pointed out that the vitality of soil cannot generally prevent fungal infestation of plants. Mildew, for example, is also problem in organic farming. TR 4 could therefore always be possible with the Cavendish variety. A solution could be variety diversification instead of industrial monoculture. Our interview partner Rudi Pfeifer, Managing Director Import/Sales at BanaFair agrees with this (see interview below).

Interview (translated from German)

Low-cost bananas are a phase-out model

Rudi Pfeifer, Managing Director Import/Sales of BanaFair e.V. was available for an interview. The non-profit organisation fairly trades organic bananas from small farmers.

Organic-market.info: Are organic bananas also affected by TR 4 fungus?

Rudi Pfeifer: In principle yes. The fungus will spread to wherever it finds favourable living conditions and enough food. In Colombia, TR 4 has so far been discovered on four plantations, including an organic plantation by Dole. According to our information, this plantation covers 90 hectares. This is obviously many times the area of small family farms. Perhaps it is more a question ofwhich organic bananas will be affected, meaning whether the way in which the organic bananas are produced plays a role, if they are grown in large-scale plantation monoculture or in rather small-scale structures, mixed cultivation or agroforestry systems.

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