A Banana-Destroying Fungus Has Arrived in the Americas

The so-called Panama disease targets bananas’ vascular systems to prevent fruit from growing

A previous strain of the TR4 fungus led banana producers to switch from the Gros Michel strain to the now-dominant Cavendish variety Steve Hopson via Wikimedia Commons under CC BY-SA 2.5

Since the 1990s, a fungus called Fusarium wilt tropical race 4 (TR4), or the Panama disease, has devastated banana plants across Asia, Australia, Africa and the Middle East, inflicting millions of dollars in damages and threatening the welfare of nations where the fruit serves as a key source of nutrition.

Until recently, TR4 had never been detected in the Americas, but as the Colombian Agricultural Institute (ICA) announced during an August 8 press conference, the deadly fungus has finally reached South American shores.

Per an ICA statement, laboratory tests revealed TR4’s presence in a 175-hectare area of Colombia’s Guajira Peninsula. Although authorities have since cleared 168.5 of these affected hectares, the state-run agency has declared a national emergency in hopes of expediting containment efforts.

As Sabine Galvis reports for Science magazine, ICA will take preventative measures including upping sanitary control at ports, airports and border entry points; increasing funding for small- and medium-size banana exporters working to introduce biosecurity measures such as disinfecting machinery, shipping containers and shoes; and closely monitoring the situation through surveillance flights and on-the-ground inspections.

It remains to be seen whether these steps will be enough to stop TR4, a fungus that targets bananas’ vascular systems to stop the plants from bearing fruit. According to Science magazine’s Erik Stokstad, TR4 spores persist in surrounding soil for decades on end, making it impossible to contain the fungus without destroying all infected plants, removing the farm from production, and blocking spores’ escape via runoff. To date, no known fungicides or biocontrol measures have 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,” Fernando García-Bastidas, a Colombian phytopathologist who organized the laboratory analysis, tells National Geographic’s Myles Karp.

Gert Kema, a phytopathologist at the Netherlands’ Wageningen University, adds, “Once you see [TR4], it is too late, and it has likely already spread outside that zone without recognition.”

Karp writes that the fungus’ arrival in South America could prove devastating to the banana-reliant region, which houses four of the world’s top five banana exporters and all ten of the United States’ top exporters. In addition to wreaking financial havoc, TR4 may spell disaster for the millions of Latin America, Africa and Asia residents who rely on bananas as a primary food source. (U.S. consumers will likely experience rising prices and lower stock, but as Karp notes, “They’ll survive.”)

Scientists have long feared TR4’s introduction into the Americas. Still, Stuart Thompson explains for the Conversation, the infectious outbreak is not wholly unprecedented: During the mid-20th century, a related strain of Fusarium wilt destroyed plantations across Latin America, paving the way for a shift from the predominant “Gros Michel” banana variety to the “Cavendish” version commonly seen today.

Cavendish bananas—currently constituting 99 percent of exported bananas and almost half of total worldwide production—are largely immune to this earlier form of Panama disease. TR4, however, impacts not only Gros Michel bananas, but the Cavendish and up to 80 percent of other cultivated varieties.

As National Geographic’s Karp reports, no new banana variety is equipped to replace the Cavendish similarly to how the now-dominant strain replaced the Gros Michel. Although sientists have experimented with TR4-resistant versions and genetically modified Cavendish bananas, the public has been reluctant to embrace these alternatives.

“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,” Rony Swennen, a researcher at Belgium’s University of Leuven who oversees a collection of more than 1,500 banana varieties, concludes to Karp. “The question is, will the industry accept it, and are the customers ready to change to another taste?”

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