published Monday, January 28th, 2013

Kudzu-killing bug may be worse than the vine

A kudzu bug, a type of stink bug, climbs on a wooden porch rail in this file photo.
A kudzu bug, a type of stink bug, climbs on a wooden porch rail in this file photo.
Photo by Associated Press /Chattanooga Times Free Press.
  • photo
    Paul Carter, forester in Fort Pickett, Va., looks over trees covered in kudzu in this file photo. Biologists have found a bug that eats kudzu, but they say it attacks crops such as soybeans, too.
    Photo by Associated Press /Chattanooga Times Free Press.

MACON, Ga. — At last, the "Vine that Ate the South" may have met its match.

To most longtime Southerners, it sounds great: a bug that loves to eat kudzu and can kill off half an infestation of the tangled vine in a couple of years.

What's not to like?

A lot, it turns out.

The bean plastapid, commonly called the kudzu bug, also likes to eat soybeans as well as wisteria and some ornamental plants. (Kudzu, wisteria and kudzu bugs all come from Asia, especially Japan.)

Like stink bugs, kudzu bugs smell bad, and like ladybugs, they try to come inside people's houses. They fly in clouds and form clumps of thousands on white homes. The insect leaves behind orange stains when smashed and gives some people a skin rash.

In a debate about which is the bigger pest, kudzu might actually lose.

Georgia is the first state the bugs invaded from Japan, and since 2009 they have spread with breathtaking speed.

Tracie Jenkins, an assistant University of Georgia professor of applied insect genetics who lives in Macon, said the earliest ones were found in 2008.

In 2009, they had become a pest to homeowners in eight or nine counties around Atlanta, where they apparently spread from Hartsfield-Jackson Atlanta International Airport.

"Homeowners were going nuts around Atlanta," Jenkins said. "Tens of thousands of these stinky little bugs were attaching themselves to the sides of people's houses." The bugs are attracted to light-colored paint on cars and houses and to tall things and people as they mate and seek crannies in which to overwinter.

Every female kudzu bug can lay 250 eggs a season, and there can be so many bugs in one infestation that a single sweep of a 15-inch-wide butterfly net gathers hundreds, Jenkins said.

Now they are found throughout Georgia and South Carolina and in six other states, as well as Central America.

The question is how to slow the spread or reduce their destructive power.

First, UGA scientists pooled their knowledge and requested help from Asian colleagues to identify the bug. Then they continued their detective work.

Jenkins examined the bugs' DNA and found that they all descended from a single female line. Then she sequenced the entire genome.

Now she's using DNA from more than 300 bugs collected in eight states, looking for genes that offer the bug resistance to insecticides, which could be targeted for changes that would weaken the insect.

Aside from changing the genetic code of the bug itself, Jenkins has identified another option. She and colleagues at other universities are working on three different kinds of bacteria that live within the bug, apparently helping it digest its food and perhaps perform other functions.

"So you have this machine with six legs and an exoskeleton, and inside you have gears made up of three bacteria," Jenkins said. Without at least some of these bacteria, the bugs would probably die, so tinkering with the gears might make the machine break down, Jenkins said.

While she pursues genetic solutions to the kudzu bug invasion, other entomologists investigate the possibility of importing another insect to prey on the kudzu bug. On its home turf, the insect is kept in check with the help of a wasp that lays its eggs in the eggs of the kudzu bug. These wasps are being tested to see if releasing them here would harm only the kudzu bug -- or some native insects as well. Jenkins said some native wasps also have laid their eggs inside kudzu bug eggs.

"Nature has a way of righting itself," she said.

Dining on soybeans

At first, it might seem that the kudzu bug itself is an example of nature correcting the kudzu problem. The insect has sucking mouth parts that it inserts into the stem.

Jim Hanula, an entomologist with the U.S. Forest Service in Athens, has found the bugs are able to reduce the size of a kudzu patch by half within two years.

"They are not going to completely eliminate kudzu," he said, but scientists want to study the long-term effect of the bugs on the vine's resilience.

Unfortunately, kudzu bugs also attack soybeans. According to the state Cooperative Extension Service, about 180,000 acres of soybeans, with a value of more than $168 million, are planted in Georgia a year. And soybean prices have been higher than usual lately.

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