But it has also stunned buyers of the root in the United States, Europe and Japan, who suddenly saw prices of processed maca shoot up, or were told that there was simply no maca left to ship to them.

Zach Adelman, the founder of Navitas Naturals, based in Novato, Calif., one of the top importers in the United States, said that his company previously paid about $3.60 a pound for maca powder. Now some suppliers are asking for more than $20 a pound.

“It doesn’t look like it’s coming down or stabilizing even,” Mr. Adelman said. At Whole Foods stores, the price of his organic maca, labeled “Incan superfood,” recently increased to $30 a pound from as low as $20. Next year, he said, shoppers will pay up to $80 a pound. “It’s going to hit them like a ton of bricks in the new year when they go and find a bag that’s three times as much,” he said.

Some scientific studies claim to show a link between consuming maca and an increase in libido. Such beliefs go back centuries. One historical account says that the Inca emperor fed maca to his troops to give them energy but removed it from their diet after victorious campaigns to tame their sexual desire.

Maca had all but disappeared as a crop by the 1980s but began a comeback in the 1990s, promoted by the government and aided by its reputation as an aphrodisiac. According to Peru’s Ministry of Agriculture, there were 6,227 acres planted with maca in 2012, up from 3,207 in 2010. Acreage appears to have grown significantly since then, and farmers said they planned to increase their plantings even more to meet the new Chinese demand.

In June, as the harvest started, Chinese buyers arrived in this town of 10,000 people, which sits at 13,555 feet above sea level on a bleak plain surrounded by windswept, dun-colored hills.