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Kudzu bugs may be expanding north and west after developing taste for soybeans

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RALEIGH Researchers at N.C. State University have determined that young kudzu bugs don’t have to eat kudzu to survive – which means they could pose a bigger threat to soybeans crops across the country than previously thought.

The Asian insect was first spotted in the U.S. just four years ago in Georgia and has earned a reputation for rapid movement, chomping kudzu vines and the occasional soybean field as it spreads across the South, as far north as Virginia.

Now researchers say the small brown bugs may be poised to follow their appetites to more northerly climes, where soybeans and other commercially grown legume crops could be at risk.

“If you give it a choice, the bug really prefers kudzu,” said NCSU entomology professor Dominic Reisig. “But there’s potential it could spread beyond kudzu’s range.”

Kudzu, a Japanese vine introduced to America during the 1876 Centennial Exposition in Philadelphia, thrives in the Southeast, growing as much as a foot per day in warm weather. In Japan, the kudzu bug feeds primarily on kudzu and to a much lesser extent on soybeans, Reisig said.

The bugs migrated from Japan to the U.S. in 2009, most likely by hitching a ride on an Atlanta-bound jet, Reisig said. Since landing, they have dined on kudzu and, increasingly, soybeans, causing crop damage as they pierce small holes in the plant to suck out the nutrients.

The bugs are also known as nuisance pests for their tendency to congregate on houses, which they may mistake for trees, Reisig says. They also secrete a smelly, caustic substance when touched.

“It’s like a chemical that leaves an orange stain on the skin and is itchy,” he said. “Some people even get blisters.”

Kudzu bugs, known scientifically as Megacopta cribaria, have an unusual two-generation life cycle, Reisig said. A group born in the fall, known as Generation A, typically feeds on kudzu vines until reaching adulthood and then moves into soybean fields. In May or June, the bugs lay eggs, which hatch into Generation B. That generation eats soybeans or kudzu from the start, Reisig said.

Research assistant Alejandro Del Pozo Valdiva worked with Reisig to conduct laboratory tests to determine the feeding requirements of Generation A pre-adult bugs, known as nymphs. “The hypothesis was they needed kudzu as an obligated host,” Del Pozo Valdiva said. “But our findings denied that hypothesis.”

Instead, the experiment showed the Generation A nymphs could reach maturity and reproduce on a soybean-only diet. That work was published in the April edition of the Journal of Economic Entomology

“We suggest in the paper that the kudzu bug won’t be limited to where there is a kudzu vine,” Del Pozo Valdiva said. “They may even begin to explore other legumes.”

The legume family includes soybeans, black-eyed peas, snap beans and other vegetables.

Reisig said the research indicates the kudzu bugs are a potential threat across the U.S., especially areas such as the Midwest, a major soybean-growing area.

Kudzu bugs, like kudzu vines, proliferate unchecked because they have no natural enemies in North America.

That’s why scientists have imported an Asian parasite, a tiny wasp that lays eggs in the kudzu bug, causing the bug’s death.

The wasp, Paratelenomus saccharalis, is now being tested in quarantined conditions at a lab in Mississippi.

“We’ve learned a lot from our mistakes [with exotic species], so there are stringent policies and procedures in place,” Reisig said. “The parasites won’t be allowed out of quarantine until we’ve done our homework.”

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