Almost alone among researchers at the U.S. Vegetable Laboratory on Savannah Highway, entomologist Mike Jackson can't track his various produce experiments in progress.

While his fellow U.S. Department of Agriculture breeders spend the last months of summer watching supposedly hardy broccoli strains wither in the sun and marveling at how well an oddly shaped watermelon withstands insect attacks, Jackson is stuck with a subterranean mystery. As the researcher in charge of sweet potatoes, he doesn't have a clue how his root-tubers are faring until a tractor plow unearths them in October.

"It's like Christmas," Jackson said on this year's harvest day, eagerly examining a few of the more than 400 turned-up specimens for size, color, pest scars and disease. The planted varieties include popular breeds from other countries, which aren't yet widely grown in the U.S.; test breeds submitted by growers and breeds developed at the lab, which is perpetually trying to devise a more vigorous sweet potato that meets the market's needs.

Last year, Jackson's crew was infatuated by a healthy, good-size sweet potato with deep orange flesh. "Then we cooked it," Jackson recalls. "Everybody's face just fell. It was awful."

Before researchers can cook up this season's crop, they have to clean, cure and thoroughly document every trial sweet potato, giving them a few more hard-working months to wonder about the results of their work.

"The possibilities are amazing," said Mark Farnham, the Vegetable Lab's lead researcher. "No two sweet potatoes are alike."

Sweetening the future

Curiosity is a constant when it comes to sweet potatoes, and much of it is now focused on the future of the industry itself. After a decade of stupendous growth, fueled almost entirely by the rise of the sweet potato fry, growers are grappling with the issues that inevitably arise when a commodity gets hot: Leaders of sweet potato trade associations say that if the sector wants to avoid stalling out, it will soon have to address significant gaps in research funding and the limited geographic reach of existing processing facilities.

"Is there enough money being put into it? No," said Benny Graves, executive director of the Mississippi Sweet Potato Council, adding, "and I'm talking about my own people."

Graves describes himself as "optimistic" but suggests the fate of one of the Southeast's defining crops may rest with its producers' willingness to invest in it. Despite the sweet potato's recent success, per capita consumption in the U.S. is 6.3 pounds, according to the USDA's most recent data. By contrast, the average American annually eats 77 pounds of white potatoes. Graves worries sweet potatoes will remain an also-ran vegetable if growers don't rally around new processing, packaging and marketing strategies.

"We're not sophisticated producers, but we've got too many good things going," Graves said. "Heck, just this week, I talked to a pet food manufacturer who wants to include sweet potatoes in his product. In the future, we might see sweet potato nutraceuticals, and we haven't scratched the surface on the export market."

No small fry

According to Charles Walker, the Columbia-based executive secretary of the U.S. Sweet Potato Council, sweet potato production nationwide has doubled over the past 10 years. While acreage slipped slightly in the most recent growing season, perhaps as a result of a dip in prices, nobody disputes the sweet potato scene has changed radically since 2001, when ConAgra started selling sweet potato fries to restaurants.

Domestic sweet potato sales have gotten a boost from Latin and Asian immigration, and a renewed interest in healthy eating has also helped propel more shoppers toward the sweet potato aisle. But nothing has been as influential as the introduction of sweet potato fries, which are so immensely popular that ConAgra in 2010 opened a $155 million plant dedicated exclusively to their production. That same year, The New York Times reported 50 percent of American children under 12 have sampled the millennial snack, laying the groundwork for a generation of sweet potato fry fans.

"The fries will continue to increase," predicts Sue Langdon, executive director of the N.C. Sweet Potato Commission. "Not exponentially, but they've found their place on menus."

Still, even maintaining modest growth will require ongoing research. Unlike growers of white potatoes, sweet potato growers rely wholly on tax-backed scientists to study how to maximize yield and minimize infestation. In the sweet potato arena, that tiny group consists of Jackson, a N.C. State University researcher, and a Louisiana State University researcher. "We're a very close-knit group," Jackson said.

With the university-based researchers dedicated to supporting their home states' growers, Jackson is the only researcher in the country working on insect resistance projects designed to benefit the industry at large. When he leaves the U.S. Vegetable Laboratory at the end of next year, he'll take a wealth of sweet potato knowledge with him.

The research void

Jackson, who switched to sweet potato studies when the federal government stopped funding tobacco research, hasn't yet formalized his retirement plans, so Farnham can't yet say exactly how the agency will handle his departure. "The intention is definitely to replace Mike when he retires," he said.

In Mississippi, the state's Extension Service this year hired a young Ph.D. holder to serve as its sweet potato specialist. While Graves applauds his home state's efforts to develop new sweet potato talent, he frets that Jackson's departure will create a "void."

"We have a limited number of people with that level of experience," he said. "It's hard to get that overnight. We hate to lose anybody because we're operating on the edge as far as research. We recognize that."

Graves and his colleagues make regular trips to Washington, D.C., to lobby for more funding, but their requests are somewhat complicated by the current composition of the sweet potato industry. Nearly all of the sweet potatoes consumed in the U.S. come from just four states: North Carolina, which produces 50 percent of the nation's supply; California, where growers cultivate breeds developed in Southeastern labs; Mississippi and Louisiana. (The Gulf Coast states are relatively small players, together producing fewer sweet potatoes than California.)

Understandably, sweet potato farmers in North Carolina and California aren't especially eager to underwrite the development of varieties which might facilitate sweet potato production in other states. But even without their involvement, the sweet potato industry is showing signs of perking up in different regions: Iowa State University recently completed its second successful sweet potato harvest, and Walker said growers of white potatoes in Washington are showing interest in diversifying.

Growing production areas

Closer to home, at least two companies have contacted Walker about the possibility of growing sweet potatoes in South Carolina.

"I don't know what happened to South Carolina," said Walker, who estimates 300 acres statewide are devoted to the crop. "At one time, South Carolina had quite a bit of acreage."

The answer is partly pest-related. Two coastal counties - Charleston and Beaufort - aren't allowed to ship their sweet potatoes because of a sweet potato weevil threat; North Carolina further prohibits the import of sweet potatoes from Colleton, Clarendon and Florence counties. "We must continue to protect this industry from potential introductions of this destructive pest," N.C. Agriculture Commissioner Steve Troxler said in his 2009 announcement of the Colleton quarantine.

Although entomologists are somewhat concerned about the weevil hazard posed by decorative sweet potato plants sold at home improvement stores, Jackson said South Carolina's weevil problem is largely contained. "It's been pretty stable," he said. Yet in South Carolina counties unbothered by weevils, sweet potato production has long been inhibited by a lack of infrastructure. There isn't a processing facility in the state, although that could change if Walther Farms decides to grow sweet potatoes on a major potato farm here.

Based in Michigan, Walther Farms owns 13,000 acres of potato fields in eight states. Spokesperson Troy Elliott declined to talk about the company's South Carolina plans, citing The State's recent coverage of Sen. Nikki Setzler's criticism of them, but Walther has proposed a 3,700-acre potato farm near Aiken.

Assuming critics aren't able to stop the company's water withdrawals, Walker suspects sweet potato growers could be the beneficiaries of a new packing house.

"If this company gets into this thing, it really could mushroom," he said. "I think sweet potatoes would be a nice crop for some of these South Carolina people to get involved in."

Reach Hanna Raskin at 937-5560.