NEW ORLEANS — Kudzu bugs, pea-sized Asian insects with hearty appetites for soybeans as well as the weed they’re named after, have hitchhiked from Alabama to western Mississippi. Farmers and entomologists in Arkansas and Louisiana are keeping a wary eye out for an invasion.

The bugs were found near Vicksburg, Miss., in July.

“That’s too close for comfort for us in Arkansas and the rest of the Mississippi Delta,” Arkansas Extension Service entomologist Gus Lorenz wrote on a blog when he learned of the Mississippi sighting. The LSU AgCenter also put out an alert asking farmers to keep an eye out for the bugs.

Vicksburg is about 270 miles west of the nearest Alabama county where they’d been seen.

Since first being spotted near Atlanta in 2009, kudzu bugs have spread to the Carolinas, southern Virginia, northern Florida, Alabama and east Tennessee. They are strong flyers, but also are known to hitchhike on trucks and other vehicles.

Such a big jump out of Alabama would be surprising if the bugs were only flying from place to place, said Wayne Gardner, an entomologist at the University of Georgia’s campus in Griffin.

“We knew these insects were very strong flyers, but we also knew they’re exceptionally good hitchhikers,” he said.

Kudzu bugs range from green to a brown so dark it’s almost black. They look a bit like ticks and a bit like dark ladybugs with squareish backsides. “If it was on you and sitting still, you might say, ‘Gosh is that a tick?’ If they were moving you might say, ‘What kind of lady beetle is that?”’ Gardner said.

Like stinkbugs, to which they’re related, and like imported ladybugs, they emit a protective stink. Gardner said it’s a fruitier smell than stinkbugs’ stench, and has been mistaken at least once, by a woman who called 911, for a gas leak. “There was no gas. But there were kudzu bugs all over her screens and door and windows and porch,” he said.

That’s another way they’re like imported ladybugs — they’ll go into buildings for warmth. They especially seem to like white and pale colors. Gardner said he’s found them on his white car after checking beans or kudzu for the bugs, which are known to scientists as Megacopta cribaria.

That’s why they were first noticed in Vicksburg, said Angus Catchot Jr., an associate extension professor in entomology and plant pathology at Mississippi State University. A woman saw them on a car at a gas station on Interstate 20, then noticed kudzu across the road.

Kudzu and soybeans both originated in Asia. Soybeans were brought in as food, kudzu for erosion control and fodder.

Kudzu bugs came to Georgia by accident. We’ll probably never know how, Gardner said, but we do know that every kudzu bug checked in North America can be genetically “traced back to one mom.”

A geneticist is working to learn which part of Asia that bug came from, he said.

So far, North Carolina, with 1,670 acres of soybeans planted this year, is the only state with both a nearly statewide invasion and more than a few hundred acres in soybeans.  But Mississippi has 2,130 acres, Arkansas 3,250, Tennessee 1,330 and Louisiana 1,140.  Arkansas has the 11th-largest acreage among 31 states that grow soybeans, according to the U.S. Department of Agriculture.

The bugs’ potential damage to the crop doesn’t seem as great as that from stinkbugs, which can destroy a farmer’s entire harvest by dissolving beans and sucking them out of their pods. Tests in Georgia and South Carolina found that, unchecked, kudzu bugs cut yields an average of about 19 percent and up to 47 percent, Gardner said.

That’s still a lot.

It can take them a while to move from kudzu to soybeans — Alabama farmers found them in fields for the first time this year, in two northeastern counties where they were found two years ago on kudzu and one where they were first found on kudzu last year  — and they’re vulnerable to products already on the market.

Although early attempts to kill them were met by almost immediate reinfestations, more recent tests indicated that it may be possible to avoid losing money to the bugs by spraying when both immature and mature insects are in the field, Gardner said.

But more tests are needed, he said: “Will that hold across the region? I don’t know. Will that hold for subsequent years? I don’t know.”