A Deadly Fungus Is Killing All Our Bananas

Hope you're not too fond of smoothies...

|
Jun 4 2015, 9:00pm

Image: Charles Roffey/Flickr

You might be glad you stored those 18 black bananas in your freezer ("in case you want to make muffins"), if a killer fungus that's wiping out the world's banana crop continues to spread.

The crop-killing, soil-borne fungus called Fusarium wilt had been killing banana plants in Southeast Asia recently appeared in the Middle East, Africa, and Australia, leaving fruit exporters baffled and nervous.

There are different varieties of bananas just like there are different kinds of apples and some of these varieties are better at fighting off some strains of Fusarium than others. The trouble is that we don't grow lots of types of bananas, we pretty much just grow one—the Cavendish. Literally, it is all the same banana: the Cavendish bananas are clones. And this banana sucks at fighting off this newest strain of Fusarium.

"The Cavendish variety is really important. It's about half of the bananas worldwide," Randy C. Ploetz, a tropical fruit pathologist at the University of Florida, told me over the phone. "About 45 percent of all banana production is of Cavendish, so even if this strain of Fusarium didn't affect anything else, it would really be important."

There are other reasons fruit producers are worried, too. Since Fusarium comes from the soil, it's difficult to detect until it's too late. It attacks the banana at the roots, infects the plant from the ground up, and kills it from the inside out. By the time a farmer realizes something is wrong, it's usually too late, Ploetz said.

It also is difficult to eradicate, he told me: some areas where Fusarium ravaged crops in the past still had banana plants becoming infected when they tried to replant four decades later.

The good news is that the fungus hasn't made its way to Latin and South America yet—by far the biggest producers of bananas in the world. But the fact that the fungus managed to travel as far as Africa and the Middle East, and that nobody knows how, is troubling, Ploetz said.

"Perhaps just mud on plantation workers' boots brought it in, but it's not clear," Ploetz said. "It doesn't take much to think, 'gee, if it made that jump, it could make the jump to the tropical Americas.'"

It seems like the obvious solution would be to switch to growing a variety of banana that isn't as vulnerable to this strain of Fusarium. That's what we did the last time a strain of the fungus all but wiped out our global crop, in the 1950s when we switched from the popular Gros Michel variety to Cavendish. There are even other strains of bananas that are supposedly better tasting than the bananas we most often find in our grocery stores, so why not make the switch? But it's not that simple, Ploetz told me. When it comes to global production, there's simply nothing that compares to the Cavendish.

"The export trades are kind of addicted to it," he said. "It produces a lot of bananas. The exporters are really good at producing it and shipping it, they've got the post-harvest technology down to a science. If we were to convert to something else, they wouldn't be able to produce as many, consumers might not like them as much. It would be really problematic."

Although the Cavendish was a good replacement for the Gros Michel, there really aren't any other varieties that come close to being able to produce bananas in the same way. Ploetz told me researchers have been trying to develop a new variety that is resistant to this strain of Fusarium but still produces as prolifically as the Cavendish, but it's not there yet.

And it's not just about Chiquita making big bucks or hipsters having something sweet to mask the kale in their smoothies: bananas are an important, affordable, and nutritious staple food for much of the developing world, including nations from which the crop is exported. Ploetz said if we had just one other, fungus-resistant variety of Cavendish, we could swap it in as needed whenever there is an outbreak.

"We need to have another fungus-resistant banana and we really don't have it right now," Ploetz said. "It's a serious problem."