18 Monoculture
18.1 Bananas
18.1.1 Panama Disease
In a long-feared development, an extremely damaging banana disease has apparently reached Latin America. Late last week, the Colombian Agricultural Institute (ICA) in Bogotá confirmed that four plantations in northern Colombia have been quarantined because of suspected infection with Fusarium wilt tropical race 4 (TR4), a fungus that kills plants by clogging their vascular system. Already widespread in Asia, the disease can wipe out entire plantations.
The finding has yet to be confirmed, but countries in the region are on high alert. Neighboring Ecuador is the largest banana exporter in the world; Colombia, Costa Rica, and Guatemala are big producers as well. A major outbreak of TR4 could ruin many farmers and drive up banana prices globally. “It poses a big threat,” says Rob Reeder, a plant pathologist at CABI, a nonprofit research and outreach center for plant diseases in the developing world, based in Egham, U.K. “This should really start raising alarm bells.” “We should take this extremely seriously,” adds Gert Kema, a plant pathologist at Wageningen University in the Netherlands.
TR4 is a variant of Panama disease, which wiped out banana plantations across Latin America in the mid-20th century. The industry recovered after it replaced the most widely cultivated banana variety at the time, Gros Michel—also known as the Big Mike—with a new one, the Cavendish, that is resistant to Panama disease and now dominates the export industry.
TR4, which easily overcomes the defenses of the Cavendish and many other banana varieties, emerged in Indonesia in the 1960s and has spread to many other countries since then. It surfaced in Jordan in 2013, in Mozambique 2 years later, and also in India, the world’s largest banana producer. Scientists dreaded its jump to the Americas, suspecting it was only a matter of time.
Fusarium is spread largely by contaminated soil and infected plant materials. It’s possible that the strain arrived with farm machinery from abroad, or was carried by traveling farm workers or tourists. Banana leaves, used for wrapping food in many countries, are another potential infection route. (Bananas themselves do not spread the disease.)
New ways to battle the scourge are on the horizon. Adding certain types of biomass to the soil and covering it in plastic can kill the spores, as the material decomposes and releases gas toxic to bacteria and fungi. In trials conducted by Kema and his colleagues in the Philippines, the technique significantly reduced the number of spores, suggesting it might help contain the disease.
The longer-term solution is the same one that saved plantations decades ago: replacing the vulnerable plants with a resistant variety. The Honduras Foundation for Agricultural Research in La Lima has spent decades breeding TR4-resistant bananas, but so far the results have not lived up to the Cavendish in properties such as taste and resistance to blemishes. A genetically modified Cavendish produced in Dale’s lab has shown resistance to the fungus in early field trials. Dale says that banana is now in larger trials; he hopes it can be commercialized in 2023. But whether consumers will buy transgenic bananas remains a question.
What’s already clear from TR4’s apparent arrival in Latin America, Kema says, is that banana cultivation cannot continue without major changes. “This is a turning point for the industry,” he says.