ROBERT SMITH, host: Walk down the produce aisle of your local grocery store. There are the button mushrooms, four bucks a pound; the shiitakes, I don't know, about double that. If you live at a fancy neighborhood, maybe there are black truffles for $800 a pound. That is nothing. There's another fungus that can fetch as much as $50,000 a pound, but it's not for the flavor.
Our producer Lauren Silverman went digging for some answers.
LAUREN SILVERMAN: In English, it's called caterpillar fungus. But Asia knows it by the Tibetan term, yartsa gunbu, which means summer grass, winter worm. And although it is a fungus, it's not the kind you might find popping up in your backyard, unless your backyard is the Himalayas.
BRITT BUNYARD: This fungus Cordyceps, they make their living by getting inside of their host insect and ultimately killing it and consuming it.
SILVERMAN: That's Britt Bunyard, a professor at the University of Wisconsin. He's got a doctorate in fungus. So, what he says this particular fungus does is take over the caterpillar's body and then erupt out of its head. And the result - a pinky-sized mummified caterpillar with this kind of toothpick sticking out of the dirt.
Britt Bunyard, who also created Fungi magazine, says this is the most expensive one in the world.
BUNYARD: The price doesn't compare to fungi. The price compares to things like gold and platinum and diamonds.
SILVERMAN: So why is it so expensive? Well, the fungus is also known as the Viagra of the Himalayas.
UNIDENTIFIED MAN: It is a faultless treasure of an ocean of good qualities.
SILVERMAN: The first mention of yartsa gunbu is from a 15th century Tibetan medical text.
UNIDENTIFIED MAN: In particular, it increases specially semen.
SILVERMAN: And the price? Well, it all depends on size.
DANIEL WINKLER: Size matters. So, the bigger the worm, the higher the price.
SILVERMAN: That's Daniel Winkler. He grew up mushroom hunting in Germany and now spends a lot of time in Tibet. Yartsa gubu has been popular for centuries in China, but he says the price has jumped by a factor of 10 over the past decade. These days, if you're a businessman in China trying to impress at dinner...
WINKLER: Cook up some nice goose or duck or something and stuff it with a load of caterpillar fungus and, you know, where the guest says or realizes, wow, I mean, this filling of the goose must be at least 500 or 1,000 bucks or something like that.
SILVERMAN: Because it is so valuable, yartsa gunbu has led to some violence. Last year in Nepal, seven men went missing after a dispute over the fungus, two of them were found dead at the bottom of a ravine. That caught writer Eric Hansen's attention.
ERIC HANSEN: I said, what the heck's going on? What is this stuff?
SILVERMAN: Hansen is a freelance writer in New York. He's lived and traveled in Nepal but never came across the prized fungus. So, he tried to find it in New York City's Chinatown.
HANSEN: Sure enough there it was. In the first herbal apothecary I went into, there were four big glass jars of the stuff selling for between $500 and $1,300 an ounce.
SILVERMAN: Hansen was so enthralled by this worm that he went back to Nepal.
HANSEN: As soon as they see that yartsa gunba is sprouting in these high, high alpine fields, the whole village just empties out. And then everybody climbs up into the mountains and spends pretty much six weeks crawling around looking for the tips of yartsa gunbu.
SILVERMAN: A good harvest can triple an individual's income and completely transform communities, like the village of Nar.
HANSEN: The whole town used its yartsa gunbu profits to buy solar panels. So now you have this centuries-old stone hamlet, and on the corner of each building is a black solar panel about the size of a board game.
SILVERMAN: Here in the U.S., yartsa gunba hasn't caught on. Mushroom hunter Daniel Winkler.
WINKLER: It's just too expensive. You really got to believe it does something for your health.
SILVERMAN: Which is exactly what the fungus doctor, Britt Bunyard, is skeptical about.
BUNYARD: There's no, to my knowledge, pharmaceutical companies in, say, the United States, that have looked into this or currently are looking into it. There's just nothing that's been found out.
SILVERMAN: So I asked Eric Hansen, who tried this stuff in Nepal, if it did anything for him.
HANSEN: Nothing. My back pain didn't ease, my eyesight didn't sharpen, I didn't feel like springing out of my chair and taking a jog, my loins were not aflame and my libido did not rage.
SILVERMAN: But so long as yartsa gunbu is all the rage in China, there are still fungal fortunes to be made.
Lauren Silverman, NPR News.
NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR’s programming is the audio.