New Strain of Banana Fungus Threatens Industry, Food Security

A recurrence of a devastating banana fungus called Panama Disease continues to destroy crops in Asia and Africa. Though this new strain has yet to majorly affect global markets, the threat is huge to both the world economy as well as food security in developing countries.

A man sells bananas in Uganda, where bananas represent a staple dietary component.

The world’s most important fruit is in danger of going extinct, again. The banana is the most widely produced fruit on Earth (with over 100 million tons of bananas being produced annually) and is worth an estimated 5 billion US dollars a year in trade. Beloved as a creamy sweet fruit in the US, annual banana consumption is greater per American (11.9 kg) than apples and oranges combined. Accounting for 99% of all bananas exported on the world market, the Cavendish banana is the only banana much of the world knows.

The Cavendish hasn’t always been the global banana of choice. In fact, the reason for this banana’s ascension is also threatening to wipe it out. 50 years ago the most popular banana in the world was the Gros Michel, a larger, creamier, more flavorful banana than the Cavendish. In the late 1950s a fungus commonly known as Panama Disease (Fusarium oxysporum), pushed the Gros Michel to the brink of extinction, and nearly took the banana industry with it. Growers searched far and wide for a variety that would resist the disease and found its solution in the unlikeliest of places; the Chatsworth House in Derbyshire, England had been growing Cavendish bananas since it received one as a gift in the 1830s, and it is believed that nearly every Cavendish grown around the world today descends from the single plant in Derbyshire.

After successfully recovering from that scare, the banana industry avoided serious threat until in the 1990s a new strain of the Panama Disease fungus. The so called tropical race 4 (or TR4) is a relatively new strain that the Cavendish has no resistance towards. Once again the banana industry is in scrambling to avoid a full scale collapse.

Today, like in 1950, the most important banana variety is known to be susceptible to a fungus that is nearly impossible to eradicate, and difficult to contain. All races of Panama Disease live in soil and infect the root system of a banana plant, eventually destroying the plant via the vascular system. The disease does not only kill the plant, it remains in the soil for decades, rendering the site unfit for banana production. Short of very invasive and destructive soil treatments (which are illegal nearly everywhere), the fungus will be present for about 30 years.

Spreading Panama Disease is really easy too. The fungus lives in soil and when contaminated dirt is carried in the sole of a shoe or the treads of a tire, for example, the spores travel with it. Water runoff carries the disease in into neighboring fields, and since bananas are grown in moist climates, heavy rainfall is a big challenge to containment . Under these conditions, stopping the spread of Panama Disease is exceptionally difficult. On a long enough time scale, the spread of the fungus across a continent is nearly inevitable.

Graphic by Braden Anderson and Andy Thies

Since Tropical Race 4 was first observed in Taiwan in 1994, some of the places the pernicious pathogen has spread are: China, Australia, The Philippines, Indonesia, Pakistan, and most recently, Jordan and Mozambique. A few major markets have already been affected by the blight. Indonesia’s exports of over 100,000 tons annually have been wiped out, causing annual losses of some $134 million in revenue in Sumatra alone. Data from 2014 indicates that TR4 was responsible for the loss of more than 6,000 hectares in the Philippines and 40,000 hectares in China. Global markets have not felt a significant effect, but major importers like Japan have seen prices increase in the last decade.

For over 500 million people, particularly in the world’s least developed countries, the banana is not a delectable dessert fruit but a starchy staple crop Eastern Africans are especially known for being heavily reliant on bananas for nutrition, where the average person may eat up to 11 bananas a day. Over the course of a year, this means that the average American eats 11.9 kg of banana while the average Ugandan eats 240 kg.

According to an interview with Beatrice Ekesa-Onyango, a Postdoctoral Research Fellow at Bioversity International who’s work focuses on Eastern Africa, “Banana is part of the diet for almost every socioeconomic group in the region, and it is cooked in so many different ways. There are over 1,000 varieties of banana, with different qualities, including nutrition value, taste, and cooking properties.”

For the parts of Africa that rely on the numerous indigenous varieties of banana for nutrition, the original Panama Disease was of little consequence, since the fungus didn’t have any effect on most varieties of banana. However, the threat from TR4 is enormous: in total, approximately 80% of the bananas produced in the world today are susceptible, and many of these are not affected by other races of Panama Disease.

Despite major efforts to keep the disease from entering the African continent, Mozambique became the first African country to report of TR4 in 2014. So far, the fungus has been contained to only the area that was originally infected, but many experts feel that it is only a matter of time before the fungus begins to spread across Africa, either by breaking containment in Mozambique or by entering another country. If, or when, the fungus takes root in East Africa, millions of people might be without their most important food supply.

The future of the banana likely depends on more than just containing TR4. As it stands today, it doesn’t appear that there is a single banana on the planet that could be used as a satisfactory successor to the Cavendish. Creating a new banana by cross breeding has shown potential, while other laboratories are searching for the solution via genetic modification. There is little doubt that with the help of these scientists, the global banana market will find a new mass production banana, and the industry will recover. There is much more uncertainty over how the millions of tons of indigenous bananas will be replaced.

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