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The ‘pandemic’ destroying the world’s favourite fruit

The banana equivalent to Covid-19 is spreading to new countries, forcing the industry to change how the world’s most widely eaten fruit is farmed and even how it could taste.

A killer disease turns up out of the blue. It moves by “stealth transmission”, spreading before symptoms even show. Once it takes hold, it is already too late to stop it – there is no cure. Life will never be the same again. Sound familiar?

Although this may sound remarkably like Covid-19, I am actually talking about Tropical Race 4 (TR4), a disease that affects bananas. Also known as Panama Disease, it is a fungus that has been rampaging through banana farms for the past 30 years.

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But within the last decade the epidemic has suddenly accelerated, spreading from Asia to Australia, the Middle East, Africa and more recently Latin America, where the majority of the bananas shipped to supermarkets in the global north come from. To date it is now in more than 20 countries, prompting fears of a “banana pandemic” and shortages of the world’s favourite fruit.

Scientists around the world are working against the clock to try to find a solution, including creating genetically modified (GM) bananas and a vaccine. But just like Covid-19, the question is not only if we can find a cure, but also how do we live with a “new normal” that will change bananas forever?

The first place to look for clues is the origin of the modern banana that we all recognise. Its history shows just what happens if this disease is ignored.

This is not the first time bananas have faced wipe-out, explains Fernando García-Bastidas, a researcher in plant health who studied TR4 at the University of Wageningen in the Netherlands before moving to a Dutch plant genetics company trying to tackle the disease. In the 1950s the industry was decimated by what he describes as “one of the worst botanical epidemics in history”, when Panama Disease first hit. The fungal disease originated in Asia, where it co-evolved with bananas, before spreading to the vast plantations of Central America.

A diseased plant is felled to prevent further spread of the fungus

The reason it was so devastating, says García-Bastidas, was because the bananas were all one variety, the Gros Michel or ‘Big Mike’. The cultivar was chosen by the burgeoning banana industry because it produces large, tasty fruit that can be cut from the tree unripe, making it possible to transport a highly perishable, exotic food long distances while it continues to ripen. Each plant was a clone of roughly the same size and shape, produced from suckers – lateral shoots that develop from the rootstalk – making it easy to mass produce. It means each banana plant is genetically almost identical, producing a reliably consistent fruit crop. 

The banana production system was weakly founded on the limited genetic diversity of one variety, making them susceptible to disease, says García-Bastidas. You would have thought the industry had learned its lesson. You would be wrong.

The search began for a variety to replace the Gros Michel that might be resistant to Panama Disease. By the 1960s, one cultivar, the Cavendish, showed signs of resistance that could save the banana industry. Named after the 7th Duke of Devonshire, William Cavendish, who grew the plant in his greenhouse in Chatsworth House (there is still one there today), the banana could also be transported green – though it had a blander flavour than the Gros Michel. Within a few decades it had become the new genetic clone for the banana industry and remains so today. But for scientists nervously watching the vast, expanding plantations, it was just a matter of time before there was another outbreak.

Sure enough, in the 1990s a new strain of Panama Disease known as TR4 emerged, again in Asia, that was lethal to Cavendish bananas. This time, with a globalised economy where researchers, farmers and other visitors to banana plantations can fly around the world, it spread even more quickly.

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Cavendish bananas are washed before being shipped from this Ecuadorian farm

García-Bastidas, who completed his doctorate on TR4 at the University of Wageningen, describes the modern banana disease, which attacks the plants vascular system causing wilting and death, as a “pandemic”.

“Bananas are undeniably among the most important fruits in the world and are a major staple food for millions of consumers,” he says. “We cannot underestimate the impact the current TR4 pandemic could have on food security.”

It was García-Bastidas who spotted TR4 outside Asia for the first time, in Jordan in 2013.

Ever since he has been “crossing his fingers” that it would not hit developing countries, where bananas are a staple food. But it is already in Africa, after being spotted in Mozambique.

The reason TR4 is so deadly is because, just like Covid-19, it spreads by “stealth transmission”, albeit on different timescales. A diseased plant will look healthy for up to a year before it shows the tell-tale signs of stained yellow, wilting leaves. In other words, by the time you spot it, it is too late, the disease will likely have already spread via spores in the soil on boots, plants, machines or animals.

García-Bastidas, who is originally from Colombia, knew that TR4 would get to the hub of banana production in South America eventually.

A farm in Australia tries to prevent the spread of TR4 by wrapping up their bananas

In 2019 his worst nightmare came true – the call came in from a farm in Colombia. Banana plants were showing wilted yellow leaves and wanted to send him samples.

“It was like a bad dream,” he says. “One minute I am on the farm, the next in the lab, the next explaining to the Colombian government minister that the worst has happened. For a very long time I could not sleep well. It was heart-breaking.”

Like every other country with TR4, Colombia is now trying to slow the outbreak as the world nervously watches for signs of the disease in the rest of Latin America and the Caribbean.

Since there is no cure, all that can be done is to quarantine the infected farms and enforce biosecurity measures such as disinfecting boots and preventing the movement of plants between farms. In other words, the banana equivalent to washing your hands and social distancing.

In the meantime the race is on to find a solution.

In Australia, scientists have developed a genetically modified (GM) Cavendish banana that is resistant to TR4. The Bill and Melinda Gates foundation is also supporting ongoing transgenic research. However, despite strong scientific evidence that GM foods are safe, the banana is unlikely to be on a supermarket shelf near you anytime soon as regulators and the public remain suspicious.

For García-Bastidas, who now works at research company KeyGene in close collaboration with the University of Wagengingen, GM is an “easy fix” that may solve the problem for five to ten years, but does not tackle the heart of the problem, which is an entire industry based on a single cloned variety of plant.

Tests are only just being developed to track TR4 as bananas have suffered from less research funding than other staple crops.

A shop in China displays a wide choice of local varieties

Instead García-Bastidas wants to introduce more diversity into the banana crop so that it is more resilient to outbreaks of disease like TR4. He points out there are hundreds of bananas with the potential for cultivation around the world. Why not use them? Already in countries like India, Indonesia and the Philippines people eat tens of different varieties of bananas, all of which offer different tastes, smells and sizes. But they are difficult to grow and export on the scale of the Cavendish, which has been bred to withstand transport across the oceans.

At his lab in the Netherlands, García-Bastidas and his colleagues are using the latest techniques in DNA sequencing to identify genes resistant to TR4 and breed bananas that may be able to withstand the disease, as well as being commercially viable.

“We have hundreds of varieties of apples,” he points out. “Why not start offering different varieties of bananas?”

The best hope is for a resistant banana for export to emerge in the next five to 10 years. But it is not a silver bullet. After facing not one, but two pandemics in the last century, this time the banana industry has to look at more than just introducing another clone.

Dan Bebber, associate professor of ecology at the University of Exeter, has spent the last three years studying the challenges to the banana supply system as part of a UK government-funded project BananEx. He says the best way for the banana industry to survive TR4 is to change how bananas are farmed.

At the moment the Cavendish bananas are grown on a vast monoculture, meaning not just TR4 but all diseases spread fast. During one growing season, bananas can be sprayed with fungicides from 40 to 80 times.

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A banana seller looks over his Lakatan bananas, which are common in Southeast Asia

“That could have huge impacts on the soil microbiota,” says Bebber. “To look after bananas you have to look after the soil.”Bebber points to reports from the Philippines that organic farms have fared better against TR4 because the microbiota in the soil are able to fight the infection. He says banana farms should be looking at adding organic matter, and perhaps planting seasonal crops between rows to increase shelter and fertility, using microbes and insects rather than chemicals as “biocontrols” and leaving more wild patches to encourage wildlife.

This may mean bananas cost more, but in the long term they will be more sustainable.

According to Bebber bananas are too cheap at the moment. Not only because the environmental cost of a chemical-heavy monoculture has not been taken into account, but the social cost of employing people on very low wages. The charity Banana Link, which campaigns on the issue, blames the supermarkets for a “race to the bottom” that has forced prices lower and lower, compromising the environment, workers’ health and ultimately the health of the banana crop.

Fairtrade bananas have gone some way to ensuring workers are paid a fair price for bananas, but Bebber says workers across the industry are beginning to demand better pay. Again, he says this feeds into TR4 as workers need to be paid fairly to ensure the farms are better managed for disease prevention.

“For years we have failed to take into account the social and environmental cost of bananas,” he says. “It is time to start paying a fair price, not only for the workers and the environment, but the health of the bananas themselves.”

Jackie Turner, a US-based filmmaker, who has been questioning how bananas are farmed since she worked on a plantation as a student, agrees the solution lies in fairness and diversity.

In her film Bananageddon, she talks to the scientists trying to stop the spread of TR4, the food security experts warning of shortages and the workers on the plantations concerned for their livelihoods.

Blue java bananas have a sweet, vanilla taste

“TR4 is a lot like Covid-19 in that there is no treatment for it,” she says. “It is a ‘doomsday’ scenario for bananas.”

After travelling the world for two years to see the impact TR4 is already having, Turner is convinced bananas need to be farmed in a different way, which means introducing new varieties.

She says this will not only be better for the environment and protect against disease, but could be better for the consumer too.

To try to encourage the public to support smaller farmers growing different varieties she has set up the Banana List. This lists the shops selling different varieties of bananas so that consumers can see what they like and start creating demand. For example, Dwarf Red, that tastes a little like raspberries, Lady Fingers, that are smaller and sweeter than Cavendish, or Blue Java, that tastes like vanilla ice-cream. The bananas are not only delicious but will help create a diverse kind of farming more resilient to disease.

For Turner, the banana pandemic could have positive outcomes if it forces us to farm bananas in a more environmentally friendly way and to eat a more diverse range of fruit.

“Maybe we eat fewer bananas and we pay more for them,” she admits. “But you know what, they will be better bananas.”