Bananas vs FUSARIUM wilt: the fight for existence

By Sara Azeem, Assistant Editor of GLOBUS

“Yes, we have no bananas
We have-a no bananas today.
We’ve string beans, and onions
Cabbages, and scallions,
And all sorts of fruit and say
We have an old fashioned to-mah-to
A Long Island po-tah-to
But yes, we have no bananas.
We have no bananas today.”

“Yes, We Have No Bananas”, composed by Frank Silver and Irving Cohn was a major hit in the United States in 1923. The lyrics, however, tell the true story of a period of utter chaos in the global banana market: when the Gros Michel variety of bananas was beginning to be wiped out by a deadly fungal disease. Fusarium wilt, or more commonly known as the Panama disease, tore through plantations worldwide, completely eradicating the Gros Michel by the 1960’s. First the leaves of the banana trees stopped growing. Then they started to curl and wilt. Eventually the trees dried out completely and died. The plants died because the channels that carry water and minerals from the roots to the leaves became blocked. Initially, it was assumed that the fungus clogs the vascular system, but it is now known that the plant itself does this, presumably in an act of self-defense. But fortunately for us, there existed another variety of banana – the Cavendish. Smaller, and not as sweet, but which proved to be immune to the fungus. Since then, the Cavendish banana has dominated the global banana market. 

Bananas are the most consumed and exported fruit in the world. In the UK, more than five billion bananas are eaten every year, and every single one of them is a Cavendish. According to the Food and Agriculture Organisation of the United Nations, the Cavendish banana accounts for 50% of global food production, while constituting almost 99% of the global export market, and is worth more than $13.6 billion (£10.6 billion). 

But now, the Fusarium fungus is back, and stronger than ever. The Tropical Race 4 (TR4) strain has overcome the resistance of the Cavendish and is now threatening to wipe out bananas as we know them. The new strain originated in Indonesia, then spread to Taiwan, where it had devastating effects, before moving onto China and the rest of Southeast Asia. Taiwan now exports a mere two percent of what it did in the late 1960s. The lethal fungus has also leapt to Pakistan, Lebanon, Jordan, Oman, Mozambique, and Australia’s northeast Queensland. South American countries are among the largest exporters of bananas to the European market, and so major efforts were taken to prevent the spread of the disease to those regions. Unfortunately, in August 2019, authorities in Colombia declared a national emergency after confirming TR4 had reached Latin America and closed four plantations in northern Colombia. Ecuador, Colombia, Costa Rica, and Guatemala are now on high alert. But only 15 % of global production are accounted for by exports, the rest are grown for domestic consumption by smallholder farmers in Asia and Africa where they are a staple crop. One can imagine the dire impact of the disease on food security and livelihoods in these regions. 

Bananas are clones, which has enabled them to be produced commercially on large scales using the monoculture model. But this very property also makes them extremely susceptible to spreading infection; all it takes is for one plant to get infected to destroy the entire plantation. Once a tree is infected, there is no way to salvage production. The plantation must be abandoned. To make matters worse, the fungus produces spores which remain in the soil for decades, rendering the land unusable for non-resistant crops. Another important genetic characteristic of bananas is that they are sterile and thus, waiting for evolution to do its thing through natural selection is not an option. Quarantining and exclusion are the mostly widely used methods to deal with the epidemic but despite strict measures, the disease can easily be transmitted from contaminated soil on boots or via an infected plant. And with increasing extreme weather events, containment is not very effective as the spores can just be carried by wind and water.

One potential solution lies in the wild Madagascan banana tree. It grows wild species of bananas that are immune to the Panama disease, but the fruits are inedible with large seeds.  Researchers are trying to create a hybrid of the two species of bananas to produce an infection-resistant strain. The problem is that only five mature Madagascan trees remain (as of 2018), warranting their inclusion in the latest official Red List of the International Union for Conservation of Nature. Different approaches are being trialed to solve this global dilemma. Some researchers are trying to develop a variant that is resistant to TR4, but, with the current adverse outlook of consumers to GMOs, getting these hybrids into the market might prove difficult. However, none of these potential solutions confront the fact that farming huge plantations of clones is an intrinsically unstable mode of production. While they may offer economies of scale and keep prices down, there is no guarantee that the fungus will not evolve to overcome these modifications. Judging by history, it probably will.

A more sustainable method could involve using more varieties of bananas and growing them alongside other crops or in alternation with them, which will ensure that the crops are not as susceptible to infection. This is viable especially because there is evidence that certain crops, like Chinese leeks and cassava, can protect bananas from TR4. Yes, prices of bananas might increase with such a production model, but the price of bananas today do not reflect the costs undertaken to grow them; they are just representative of a flawed system which has the potential of entrenching us in a vicious cycle.

Header image: by Aleksandar Pasaric, from Pexels

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