Panama Disease TR4 arrives in the Americas

A fungus that has wreaked havoc on banana plantations in the Eastern Hemisphere has, despite years of preventative efforts, arrived in the Americas.

In August 2019, authorities in Colombia confirmed that laboratory tests have positively identified the presence of so-called Panama disease Tropical Race 4 – or TR4- 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 disaster for bananas as both a food source and an export commodity. Panama disease 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 from 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, everybody is doing a good job in terms of containment, but eradication is almost impossible," says Fernando García-Bastidas, a Colombian phytopathologist.

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 monocultural plants’ identical genetics mean they are also identically susceptible to disease. The practice of growing crops with limited genetic diversity 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.