Aug. 13, 2019
A fungus that has wreaked havoc on banana plantations in the Eastern Hemisphere has, despite years of preventative efforts, arrived in the Americas.
ICA, the Colombian agriculture and livestock authority, confirmed on last Thursday that laboratory tests have positively identified the presence of so-called Panama disease Tropical Race 4 on banana farms in the Caribbean coastal region. The announcement was accompanied by a declaration of a national state of emergency.
The discovery of the fungus represents a potential impending disaster for bananas as both a food source and an export commodity. Panama disease Tropical Race 4—or TR4—is an infection of the banana plant by a fungus of the genus Fusarium. Although bananas produced in infected soil are not unsafe for humans, infected plants eventually stop bearing fruit.
First identified in Taiwanese soil samples in the early 1990s, the destructive fungus remained long confined to Southeast Asia and Australia, until its presence was confirmed in both the Middle East and Africa in 2013. Experts feared an eventual appearance in Latin America, the epicenter of the global banana export industry.
“Once you see it, it is too late, and it has likely already spread outside that zone without recognition,” says Gert Kema, Professor of Tropical Phytopathology at Wageningen University in the Netherlands whose lab analyzed soil samples to confirm TR4 in Colombia, as well as in earlier outbreaks.
No known fungicide or biocontrol measure has proven effective against TR4. “As far as I know, ICA and the farms are doing a good job in terms of containment, but eradication is almost impossible,” says Fernando García-Bastidas, a Colombian phytopathologist who coordinated testing.
Banana agriculture is itself partly to blame for the potential of the fungus to spread. Commercial plantations grow almost exclusively one clonal variety, called the Cavendish; these plants’ identical genetics mean they are also identically susceptible to disease. The practice of growing crops with limited genetic diversity—technically called monoculture—aids in cheap and efficient commercial agriculture and marketing, but it leaves food systems dangerously vulnerable to disease epidemics.
Consumers in importer nations like the United States might eventually be disheartened to see higher prices and scarcer stocks of bananas for their toast and smoothies, but they’ll survive. For millions in Latin America, the Caribbean, Africa, and Asia, however, bananas are a fundamental source of nutrition.
Besides the Cavendish bananas that dominate modern supermarket shelves, residents of banana-producing nations rely on a multitude of local varieties, including plantains, for their food security. Panama disease TR4 has a notoriously broad host range, meaning it threatens nearly all of these varieties to some degree.
Not just for eating
Latin America depends on bananas not only as a food source but also as a primary economic resource. The region contains four of the top five producers of bananas for the export market, and all of the top 10 banana exporters to the United States. Ecuador, which shares a border with Colombia, is the world’s largest exporter. The proliferation of TR4 in South and Central America could cause widespread economic distress.
The situation would not be entirely novel. In the first half of the 20th century, an earlier strain of Panama disease—now known as Race 1—nearly eradicated the global supply of the Gros Michel banana, which was then the only banana exported to the United States and Europe.
Desperate, the predecessors of Chiquita and Dole switched production to a banana they knew to be resistant to Panama disease, despite its relatively bland flavor: the now-ubiquitous Cavendish. TR4, the latest strain of Panama disease, spares not even the Cavendish.
Unlike in the earlier Panama disease epidemic, this time, there’s no ready replacement banana to bail out the industry. Although thousands of banana varieties grow around the world, only a few have the precise characteristics necessary to withstand the rigors of large-scale commercial cultivation, long-distance transport, and international marketing. A banana with those characteristics, a taste and appearance similar to the beloved Cavendish, and resistance to TR4 does not exist.
No replacement banana
Because bananas reproduce asexually, breeding new varieties is an incredibly difficult and time-consuming task. Scientists at the Honduran Foundation for Agricultural Research, or FHIA, have developed bananas that tolerate TR4 and other diseases, but these may be too unfamiliar to appeal to consumers and farmers. During the 1990s, a development project brought small quantities of FHIA’s Goldfinger and Mona Lisa bananas to market in Canada, but shoppers didn’t bite.
Other scientists—most notably, James Dale of the Queensland University of Technology in Australia—are testing genetically modified disease-resistant Cavendish bananas, but public acceptance of GMOs could prove a significant obstacle to their widespread adoption. Varieties created in Asia through a method called somaclonal variation are only partially resistant and have less-than-ideal agricultural qualities.
Regardless of the method used, creating just one viable replacement is not a long-term solution. “We need to deploy the rich biodiversity by generating a suite of new banana varieties, not just one,” says Kema. “Monoculture is by definition unsustainable.”
Consumers and industry stakeholders may love the Cavendish banana, but a steadfast adherence to a Cavendish ideal may prove to be myopic.
“I’m not saying we have a standby Cavendish to replace the current Cavendish, but there are other varieties with other colors, and other shapes, and other yields, which will survive TR4,” says Rony Swennen, a professor at the University of Leuven who maintains the International Musa Germplasm Collection, a collection of more than 1,500 banana varieties. “The question is, will the industry accept it, and are the customers ready to change to another taste?”
As Panama disease TR4 makes its way around Latin America, we may soon have no choice.