Illimitable Dominion Over All Bananas
The fungal disease that wants to erase bananas forever and cannot be stopped
Banana farmers and bananas around the world quake in fear. What are they afraid of? That an old enemy may reemerge and take down the whole banana system. This old banana bogeyman has a name: Panama disease.
This Southeast Asian plant disease earned its name by scourging Central American banana growers for decades after its accidental introduction. In the 1950s, the dominant food banana -- the Gros Michel "Big Mike" cultivar -- was almost completely wiped out by an outbreak of the disease.
What is it?
Panama disease is a systemic wilt disease that infects banana plants (Musa spp.). Wilt diseases attack the vascular systems of plants, ultimately killing the plant. Panama disease's pathogen enters the plant through the roots. Once the plant is infected, symptoms present externally with the yellowing of the leaf and the bending at the petiole; some cultivars maintain green leaves, but the bending at the petiole is consistent. Inside the plant, the vascular system becomes discolored and yellow starting in the roots. As the pathogen advances in the plant, and blocks the intake of nutrients, the discoloration proceeds to a reddish-brown. Eventually, all the structures of the plant will become weakened, leading to a complete structural collapse and death. Recovery from the disease is extremely rare.
The Perfect Storm
Since banana cultivars are propagated asexually, without seed or sexual reproduction, the plants are practically identical genetically. Homogenous populations like this are incredibly vulnerable to pests, and Panama disease is no different. The fungal pathogen asexually disperses its spores readily through the population, infecting new plants. The spores travel easily in water and through human intervention to new areas. The pathogen can live in soil for decades. It also persists in other plants that surround growing areas. The spores can also survive inside cloned propagules taken from infected plants, causing attempts to restore populations to fail.
Yes! We have no bananas!
In the first half of the twentieth century, however, American companies sought to dominate the production of Gros Michel bananas. Wars were fought, and governments were overthrown to make room for banana-friendly regimes. But Panama disease ripped through those homogenous plantations easily. After that, the Gros Michel fell out of favor for the Cavendish cultivar, which was more resilient against the disease. While not completely extinct, you would be hard pressed to find a Gros Michel banana in a supermarket today. The Cavendish is the now banana that consumers are most familiar with.
In 1989, a new strain was discovered in Taiwan that kills the Cavendish banana. Since its discovery, a new outbreak of Panama disease has moved through countries that grow and export bananas. And this time there is no new cultivar that can be brought to market as an alternative.
Once you see it, it is too late
Fungicides have been ineffective in controlling the spread of the disease. While efforts are being made to develop banana plants that are resistant to the pathogen, current populations of banana are fairly homogenous due to clonal reproduction. Without the natural genetic diversity, it has limited the ability to create new varieties. New varieties have been grown in labs with limited success.
The only method of controlling Panama disease is to control the spread. This means regulation and biosecurity; it means inspection and quarantine. In the United States, a Federal Order prohibiting the trade of banana plants from countries with known occurrences of the disease became effective on May 21st, 2021.
But... who cares?
This is a case study. What happened to bananas represents serious vulnerabilities in our modern industrial food system. Bananas are cheap for Americans and are a ubiquitous fruit in households. And while bananas may represent a luxury import to Americans, they are an important crop in the regions where they are grown. The new outbreak of Panama disease also affects plantains, which are an important staple crop in many of these countries.
