Kudzu bugs are N.C.’s latest imported scourge

Kudzu bugs are munching soybeans and spreading rapidly

jprice@newsobserver.comMay 28, 2012 

  • Where the bugs are This time of year, homeowners may find kudzu bugs feeding on wisteria or massed on home siding or plants they aren’t feeding on. In the fall, they also infest the inside of homes near soybean fields. Dr. Mike Waldvogel, N.C. Cooperative Extension entomologist and N.C. State associate professor, said that researchers are still trying to determine which chemicals are best for controlling the bugs. For now, to treat the insects on outdoor plants he recommends picking an insecticide labeled for the specific type of plant that is infested. He recommends against using pesticides indoors, and says the best option is prevention, by sealing openings such as those around plumbing and air conditioner lines keep the bugs from coming inside. If they do get in, you can vacuum them up and throw out the bag. More information about kudzu bugs on crops:ipm.ncsu.edu/cotton/insectcorner/PDF/Kudzu%20Bug%20Handout_Field%20Crops.Final.pdf More information for homeowners about controlling kudzu bugs: www.ces.ncsu.edu/depts/ent/notes/Urban/kudzubug.htm

Poison-spined lionfish. Swarming feral pigs. Giant cannibal shrimp.

So many weird creatures from somewhere else have been causing problems in North Carolina lately that perhaps the latest twist was inevitable: An old invasive species is being attacked by its own invasive species – which also happens to harbor an invasive bacteria that itself could be trouble.

That famed Asian interloper, kudzu, is being assaulted by, yes, a “kudzu bug.”

And it’s spreading rapidly. Moving north from the Atlanta area – where it was first found in 2009 – it had reached just one of the state’s 100 counties in 2010, Macon. Last year, it was in about half the counties, and now it’s moving into the rest.

The bugs hatch two generations a year. They are gifted hitchhikers and strong flyers, and easily by wind, said Dominic Reisig, an N.C. Cooperative Extension entomologist and N.C. State University assistant professor.

“Last week, we found them north of the Albemarle Sound for this first time, and it looks like they will probably be distributed throughout the entire state by the end of this year,” he said

Which might be fine if the ladybug-sized critters didn’t exude a stinking, caustic substance that can raise welts on humans. And if they lunched solely on their seemingly uncontrollable namesake vine.

But the bugs – which sport what researchers call “piercing-sucking mouthparts” – have developed a palate for a major crop that for mysterious reasons it didn’t like in its native Japan: soybeans.

They also feed on wisteria and like to congregate and loiter in large masses on home siding. They like light-colored surfaces and will rest on plants they don’t eat, such as fig and magnolia trees, crape myrtles, grapes, wheat, cotton and corn.

Except for their macabre feeding equipment, the brown-green bugs, seem innocuous.

They are not.

$500M soybean crop at risk

The nuisance to gardeners and homeowners is real, but much of the worries about the kudzu bugs center on the state’s $500 million soybean crop.

They have appeared so quickly, and their behavior in attacking soybeans was so unexpected, that it’s not clear yet what farmers can or should do to fight them off, Reisig said.

Crop consultant Bill Peele, president of Impact Agronomics in Washington, works with farmers in three counties. He said he hadn’t seen any kudzu bugs until last week but already, he said, they are showing up in large numbers.

At one farm near the Beaufort County town of Pantego, there were “gobs and gobs of them” on the edge of soybean fields, he said.

Farmers obviously could use insecticides, he said, but they have to be careful about harming insects that are beneficial to the soybeans.

The swarms in Pantego weren’t on the plants, for the most part, so the farmer was able to spray them, he said. But the fight is hardly over, as inevitably some were able to lay eggs among the soybeans.

Now, Peele said, he and the farmer are waiting to see what will happen when eggs hatch.

The plants are just starting to flower, and if the bugs feed on them as the bean pods are forming, that would cut the yield, but by how much is anyone’s guess.

In Japan, the bugs have long been studied, but they don’t attack soybeans there, Reisig said.

Here, though, they appear to be using a bacteria they brought with them to signal to their offspring that soybeans are good eats.

Researchers are still studying how it works, but they believe the mother places the bacteria near its eggs, and when the youngsters emerge the bacteria somehow signals what they should eat, Reisig said.

Bugs suck life out of plants

The bugs don’t chew on plants; rather, they suck moisture and nutrients from stems and leaves. That means they don’t really kill the kudzu or soybeans, but can stunt their growth and cut into soybean yields.

Chemicals they exude also probably tell them where to congregate, he said. Sometimes thick swarms will be found on one plant, and no bugs on the plant beside it. Or a swarm might be thick on the side of one house, but not next door.

When disturbed, they emit some sort of chemical that can irritate skin and stain it yellow. Plus, it smells, Reisig said, like industrial-strength drain cleaner.

Reisig, who specializes in insects found in soybean crops, has been trying to figure out what to tell farmers about the bugs.

Entomologists in North Carolina and in South Carolina and Georgia are teaming up to try to come up with approaches for growers to use to control the bugs, as well as information on how much or little damage they might do.

“Right now, farmers are hungering for information,” Reisig said. “I visited a few last week and you have to make at least an educated guess to tell these growers something.

“I like to make recommendations backed up by data and facts, but we’re kind of in the starting blocks right now,” he said.

In the long term, one approach might turn out to be using the bacteria that lets them eat soybeans as a weapon. Scientists may be able to manipulate the bacteria to trick the kudzu bugs into not eating soybeans, for example. Researchers also are experimenting with a wasp whose larvae attack the kudzu bug embryos.

“I don’t think there’s anything we can do to have an effect on the meta population on this species,” Reisig said. “Farmers will take care of local infestations of their crops, but it will be in kudzu and wisteria in the wild, it will be around homes and gardens and short of searching them out on every legume in the landscape, there’s no way to eradicate them.”

Price: 919-829-4526

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