Dr. David Orr, a North Carolina State University entomologist, is hot on the trail of a biological control for kudzu.

So far that trail has led him from N.C. State to the remote, rugged regions of China’s Anhui Province and to the pages of a recent Smithsonian magazine.

Kudzu is the deep-rooted, super-fast-growing vine that overruns land disturbed by construction or agriculture, especially in the southern United States, at the rate of a foot a day.

In Smithsonian’s October issue, Orr, a professor in the College of Agriculture and Life Sciences’ Entomology Department, characterizes kudzu as “a black hole for biodiversity.”

While he’s looking for insects that might play a part in kudzu’s potential demise in the South, in China its most efficient destroyer is humans. In fact, Orr said, the major agent of kudzu’s spread is identical to its possible ultimate killer: human activity.

“One of my graduate students recently discovered that, due to insect activity, very few kudzu seeds have the capacity to germinate. And we’ve known some time that kudzu seeds are difficult to germinate when planted,” he said. “But all it takes is one clump of root in some dirt dumped somewhere in a construction project.”

And since construction projects in the South aren’t slowing any faster than kudzu’s growth rate, Orr stays on the trail of a kudzu killer.

His research shows that although most of the kudzu that has overrun the South is descended from plants intentionally introduced from Japan in 1905, the plant’s origin is China. That’s where, 100 miles west of Shanghai, he has set up a plot with Chinese researchers near the Yangtze River. He maintains other plots in the Taibai Mountain Forest National Park in the western Shaanxi Province.

“We wanted to see if there is any biotic factor that suppresses kudzu, and the place to look for a plant’s natural enemies in its center of origin,” Orr said. To make the proper comparisons, he and his assistants had to be certain the kudzu found in China is the same plant found in the United States. Unfortunately, data from very preliminary tests indicate the two may not be identical.

“The Chinese, who harvest an incredible amount of kudzu every year, differentiate between ‘water’ and ‘fiber’ kudzu. The water variety has a starchy root that slices like a potato” and is used for food and medicine, he said. “The fiber type’s root is so tough that it’s hard to cut with a knife. If it turns out that the U.S. type is fiber kudzu, we might not be able to control it with utilization programs.”

While the Chinese sometimes search out and devastate kudzu patches in their national forests for food and medicine, it’s not generally craved as an appetizing dish in the United States. That’s too bad for kudzu control, because the Chinese use water kudzu for food almost to the point of extinction.

Medicinal uses also have contributed to the plant’s near extinction in China.

The China-based Tianfang Co. sells kudzu root extract — Wild Radix Puerariae Powder — according to advertising on its red box, to “quench thirst, dispel effects of alcoholism and arrest diarrhea” and “for the common cold, fever, headache” as well as a host of other purported uses.

In the United States, kudzu’s powdered root sells as a food supplement, sometimes advertised as an alcoholism treatment. No proof from human clinical trials supports such claims, however, Orr said.

In China, the powder’s price per gram is less than a penny; in the United States, it’s about five cents a gram, and capsules sell for 28 cents per gram.

To finish off kudzu in the United States, Orr is betting on two Chinese beetles: One attacks only large vines where they attach to the root; the other attacks the roots.

But insect controls set off little warning buzzers in researchers’ heads. “The community of insects that eat kudzu is pretty much the same one that feeds on soybeans, another plant of Asian origin,” Orr said. “We still have to do host testing to be sure they don’t attack anything else, and we do all that testing in China before we even consider bringing anything here.”

That means that even when Orr discovers the appropriate kudzu-munching insect, it must pass extremely rigid, time-consuming tests by, among others, the U.S. Department of Agriculture’s Technical Advisory Group for Biological Control Agents of Weeds.

Orr cited a maxim that, if followed a century ago, would have denied kudzu’s stranglehold on the South in the first place: “The research can take years, but better safe than sorry.”

—Art Latham