Last spring the Peruvian government announced that they had detected a much-dreaded plant disease in the country’s Piura region. A few banana trees in a small plantation had dried up, quite suspiciously. Laboratory analysis showed the trees were infected by a fungus––the Fusarium oxysporum f. sp. cubense of the Tropical Race 4 (TR4) strain, a.k.a. the dreaded “Panama disease.” The trees were quickly uprooted, and the country, which relies on organic banana production for its economic survival, declared a state of emergency.
TR4’s soil-borne fungus attacks banana trees from the roots. It slowly colonizes the lower extremities of the plant and blocks the xylem (vessels used by the tree to channel water and nutrients), leading to a slow death by choking.
Even though the fungus doesn’t reach the fruits, and doesn’t create any health danger for consumers, it can have an enormous impact on the availability (and cost) of bananas in our supermarkets. A few years from now, will we still be able to eat our favorite naturally portable breakfast or enjoy a classic banana pudding for dessert?
“We fear how quickly this disease can spread,” says Diego Balarezo Camminati, the administrator of Cluster de Banano Peru, a non-profit organization that works with about 7,000 small-scale organic banana farmers who could fall into bankruptcy if the disease upends production. “We worry about the damage it can do to the country’s food security.”
After Colombia, Peru was the second country in Latin America to officially spot the new strain of fungus on their farms. Most producers, like in most countries around the world that export bananas, grow the Cavendish—the large yellow fruit we find in supermarkets that accounts for 40 percent of the world's bananas and dominates global exports with $12 billion per year. TR4 has no mercy for the Cavendish.
This isn’t the first time a popular banana variety has faced potential extinction. Until the 1950s, one banana variety called Gros Michel dominated the world export market of bananas. Then earlier strains of the Panama disease took hold. At first, producers began indiscriminately clearing parts of pristine forests in order to keep planting Gros Michel on uncontaminated lands but without much success. Not only was the fungus killing bananas, it was now also fostering deforestation. The disease followed wherever people went, attached to their boots, inside the earth that clung to the roots of plants as they were exported around the globe.
However, as Gros Michel succumbed to the disease, researchers discovered that one of its sister varieties, with similar yields and taste, proved resistant. This was the Cavendish. Its sprouts were quickly distributed among growers around the world, and the banana industry let out a sigh of relief and began producing again. Thanks to its resistance to the first two strains of the Panama disease, Cavendish conquered the world market as the new most loved banana: a quick swap from one massive monoculture to another. But cultivating only one variety again, instead of preserving biodiversity by coming up with a more varied set of solutions, has proved to be a short-sighted solution. So here we are again.
“Forty years later, the Tropical Race 4 appeared, and it was virulent for the Cavendish as well,” says Giovanni Bubici, a researcher on soil-borne plant pathogens at the Italian Institute for Sustainable Plant Protection.
TR4 was first discovered in the 1990s, affecting Cavendish in Taiwan. It spread quickly, to Malaysia and Indonesia, India and Israel, Mozambique, Colombia, and Peru. Today, the disease is present in 20 of the 150 countries producing bananas—and its spread shows no sign of stopping. The banana industry in Latin America particularly pays attention to the fungus “because entire countries and regions base their economy on banana production,” says Bubici.
Once the fungus enters a plot of land, it is hard to control and almost impossible to eliminate. According to Bubici, chemical fungicides have been ineffective in containing the disease because it can survive in soil for more than 20 years. Due to the movement of irrigation water and machinery, the disease can spread within plants and conquer new parcels of land. This is why Bubici, collaborating with an international team of scientists on the Microbial Uptakes for Sustainable Management (MUSA), began studying alternative, less invasive ways to control the fungus.
One way was to introduce microorganisms—like pseudomonas and trichoderma—that make the banana plant more resistant to the disease. Rather than harming the plant, these microorganisms help it produce antibiotics and compete with the “bad guy” for space and nutrients. Another method is to genetically modify the plants, according to James Dale, a biotechnologist at the Queensland University of Technology in Brisbane, Australia. He is currently seeking approval from the Australian government for a Cavendish varietal he’s modified to be highly resistant to TR4.
So what happens if the scientists’ work does not quickly help prevent or contain the disease?
Luis Ernesto Pocasangre, a professor at EARTH University in Costa Rica, is not too concerned about people finding bananas in their supermarkets. He believes that some banana varieties will still be produced in the future, though it won’t be as easy as it has been in the past. “Bananas will be here forever,” he says. “But producing bananas will be more difficult with this disease," Pocasangre said.”
But he worries about small-scale organic farmers like those in Peru who make their living off of the crop. Pocasangre has worked with Panama disease prevention campaigns for governments and banana producers worldwide, and during his fieldwork, he noticed that industrial farms were more likely to control the fungus from entering their fields than small organic farms: tougher prevention routines, like sterilizing the boots of people coming in and out of the fields, made a big difference in the prevention fight.
Since TR4’s detection in Peru, Pocasangre noticed that large-scale buyers and distributors have been discriminating against bananas coming from infected areas, suddenly dropping orders from small-scale farmers, maybe for fear of being associated with an infected land. The banana fruit carries no disease, but this discriminatory trend is hitting farmers hard.
The underlying problem, researchers point out, is our food system’s reliance on monoculture. Similar examples abound, from olive trees in Southern Italy to orange trees in Florida.
Perhaps, then, we should look to countries like Uganda, where there are about 95 varieties of banana, with most small-scale farmers growing several types on their lands. According to Edie Mukiibi, a Ugandan banana farmer and the president of Slow Food International, a non-profit organization protecting local foods and traditions, this kind of biodiversity can save farmers from economic collapse. Although TR4 has not yet been detected in Uganda, the previous strains have—and Ugandan farmers have learned how to live with them.
“This is the beauty of planting different varieties [following] our traditional system, because we know different bananas respond differently to different environmental problems,” Mukiibi says. “At the end of the day, you will still have some bananas to feed your family, you will have some bananas to take to the market, and then life will go on.”
Bubici believes that African banana biodiversity can play an essential role in the containment of the pathogen’s spread, but only in specific local scenarios like Uganda, where bananas are a staple food and part of the culture.
Of course, Uganda alone cannot provide bananas to the whole world. But if other countries followed its example—trading in unsustainable monocultures for the long-lasting benefits of biodiversity—we just might ensure the long-term survival of our beloved yellow fruits.