Kudzu: The Guest That Just Won’t Leave

From USFS Southern Research Station

Posted on April 9, 2013 by zhoyle

 

Kudzu infestation in North Carolina. Photo by Barry Rice, courtesy of Bugwood.org.

Spring is right around the corner, and in the South, “all eyes… turn to kudzu… as it awakes,” says James Miller, research ecologist (emeritus) for the U.S. Forest Service Insects, Diseases, and Invasive Plants unit.
Introduced to United States at the 1876 Centennial Exposition in Philadelphia, kudzu was touted as a quick-growing ornamental vine with fragrant blossoms and broad leaves which provided abundant shade. At the turn of the century, the U.S. government promoted kudzu to help reduce soil erosion and provide an inexpensive forage crop for livestock in the South.

By 1946, some estimated that the vine covered over 3 million acres of land. Today, it’s estimated to occupy 7 million acres and covers 50,000 new acres each year! And that’s the problem: with an average growth rate of a foot per day, kudzu quickly establishes itself as a dominant plant, blocking out sunlight and obliterating other plants. It overtakes landscapes, creeps up telephone poles, and engulfs street signs and abandoned buildings.

So how do you get rid of such an imposing guest? Well, some are easier to usher out than others, but kudzu proves to be one of the hardest. Miller spent over 40 years studying invasive plant management, and he admits that “nothing eradicates it 100 percent.” Kudzu has no native predators and is resistant to the effects of cold weather. 

Early effort to control kudzu? Photo from USDA NRCS Archive, courtesy of Bugwood.org.

The most effective eradication and management options include livestock grazing or herbicides, but prescribed burning, disk harrowing, plastic sheeting, and mechanical removal techniques may also be used. Land owners and managers must choose an option that best fits the conditions in a given landscape. Further complicating the issue is the fact that successful eradication requires that “every kudzu plant in and around a patch must be killed or removed to prevent reoccupation,” says Miller. Thus, at some point, robust plants like fast growing pines, native shrubs, or perennial grasses must be established to overtop or suppress remaining kudzu to restore an area.

Recently, a new management option is being explored. An accidentally introduced insect has shown promise in the battle with kudzu. Entomologists Jim Hanula and Scott Horn—both with the Forest Service Southern Research Station (SRS) Insects, Diseases, and Invasive Plants unit—worked with Yanzhuo Zhang, a postdoctoral associate at the University of Georgia, to investigate the impact of the bean plataspid, aka “kudzu bug” (Megacopta cribraria), on the growth of kudzu. “We found that unprotected plots had 40 times the number of bugs than sprayed plots and a third less kudzu,” says Hanula. “We were actually surprised that this insect had such an impact in only one growing season.” 

Jim Miller with kudzu. Photo by Erwin Chambliss.

In 2010, SRS published A Field Guide for the Identification of Invasive Plants in Southern Forests. Miller, lead author of the guide, is one of the foremost authorities on invasive plants in the South; co-authors are SRS research technician Erwin Chambliss and Auburn University research fellow and extension specialist Nancy Lowenstein. The book provides information on accurate identification of the 56 nonnative plants and groups that are currently invading the forests of the 13 Southern States. It lists other nonnative plants of growing concern.

The information included in the guide is now available as a free application for iPhones, iPods, and iPads called Invasive Plants in Southern Forests.
Recommendations for prevention and control of these invasive species are provided in a companion booklet, “A Management Guide for Invasive Plants of Southern Forests,” which Miller co-authored with Steven Manning, president of Invasive Plant Control, Inc., and Stephen Enloe, Auburn University weed management extension specialist.—Maureen Merriman

For more information, email Jim Miller at jameshmiller@fs.fed.us.

Read an earlier CompassLive story about the kudzu bug research by Hanula and Horn.

Access the latest publications by SRS scientists.

Scientists trying to thwart kudzu bug's destructive march

From The Telegraph - Middle Georgia's News Source 

By S. HEATHER DUNCAN — hduncan@macon.com

 

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 suburban 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 bug’s entire genome. The detective work can be more fun than the field work in this case. Jenkins gathered hundreds of kudzu bugs from a foreclosed house overrun with kudzu in an upscale north Bibb County neighborhood. Driving them home, bagged in freezer bags, left her car reeking. She stored them on ice in a cooler that she subsequently had to throw out.

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. Jenkins wants to examine the genetic diversity of the bugs -- variations in their genetic building blocks -- using DNA from not only the Southeast but also from kudzu bugs from China, India, South Korea and even Honduras. Bugs apparently came from those countries to Atlanta by plane.

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. Kudzu relies on its root system when its leaves die back each winter. If bugs aggressively feed on it year after year, that could reduce the energy reserves in the plant’s roots, allowing trees to grow through the vines, Hanula said.

Unfortunately, kudzu bugs cause the same kind of stress to soybeans, diverting the plant’s energy from bean production and reducing yield. 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.

UGA entomology professor Phillip Roberts said scientists in Tifton have conducted 24 field trials over the past three years, concluding that the kudzu bug causes a 20 percent loss in soybean yield if farmers don’t spray infested areas. He said research from the most recent growing season suggests that soybeans planted earlier will be less susceptible to kudzu bugs.

He said he hopes next year to figure out more about the “sweet spot,” when the bugs are done moving and a single spray could eliminate them from a field for the year. Roberts said a $10-per-acre insecticide treatment at the right moment in a few fields around Tifton saved 20 bushels an acre -- about $300 worth of yield.
What Roberts learns could be important not only for Georgia farmers but also for Midwestern farmers, whose soybean crops are much larger.

The kudzu bug is expanding its range rapidly and likely will move anywhere kudzu lives, Jenkins said. The ease of international travel, combined with global warming, probably will expand the range of invasive species like the kudzu bug that rely on a temperate climate. Georgia’s own springs are coming a month sooner, and summers are ending a month later than in the past, she noted.

In Dodge County, where about 3,500 acres were planted in soybean, growers were fortunate that the bugs became most active after beans had already set, county extension agent Greg Slaughter said.
In Taylor and Peach counties, farmers were not so lucky.

“It’s amazing how quickly they have adapted and overrun us,” said Jeff Cook, the county agent for both. He said almost all his farmers sprayed for kudzu bugs, which became prevalent when the plants were still seedlings.

In fields near kudzu, he said, “you could drive by the field and smell them. You could easily find 10 to 20 on a plant.” The kudzu patches themselves looked as if they’d been hit by frost in the summer.

Cook said the bugs probably did reduce crop yields. He said the soybeans probably should have been sprayed sooner, but farmers were trying to reduce their costs by conducting all their fungicide and insecticide treatment at once.

“Soybeans used to be something we planted and went and tended our cotton and corn,” Cook said. “Now, all the time it’s a few more dollars we’ve got to throw out in the field.”
 
But Cook doesn’t have to drive to a soybean field to find kudzu bugs.

“I have a white house, and when the day warms up they’ll be like gnats,” he said. They killed his chrysanthemums and ate his peppers and wisteria. He has to spray his window screens, soffits and window edges with pesticide.

“I have a kudzu bug graveyard around my house,” he quipped. They even get under the straps on deer stands.

“It would be great if we could get rid of them,” Cook said. “But they’re here to stay.”

To contact writer S. Heather Duncan, call 744-4225.

Read more here: http://www.macon.com/2013/01/02/2303333/scientists-trying-to-thwart-kudzu.html#storylink=cpy

Kudzu vine key to kudzu bug’s survival

University of Georgia  |   July 3, 2012 

U.S. Forest Service entomologist Jim Hanula may be the only person in the South who actually wants to keep kudzu alive.

He needs healthy plots of the famous weed to monitor the effect the bean plataspid—a pest that entered Georgia some two years ago and has become known as the kudzu bug—is having on kudzu.

“Kudzu is known as the vine that ate the South. The roots can grow 12 feet deep and weigh 300 pounds,” said Hanula, who has an adjunct appointment with the University of Georgia College of Agricultural and Environmental Sciences.

Kudzu, and the new pest that feeds on it, came to the U.S. from Asia. The U.S. government promoted kudzu for erosion control in the early 1900s, and by 1946 the vine had spread or was planted on 3 million acres of land, he said. It now occupies 7 million acres and covers 50,000 new acres each year.

Since the bean plataspid arrived in Georgia, Hanula has been knee-deep in kudzu patches trying to learn about the bug’s life cycle and behavior—and how it affects kudzu health.

The pest eats the vine, but it overwinters on the bark of nearby trees. Those that survive winter lay eggs on kudzu in the spring. Their young, called nymphs, feed on kudzu and emerge as adults in late June and July. The insects then go through the same process again, with the next generation of adults emerging in September and October.

“It is these adults that will overwinter and start the whole process next year,” Hanula said.

Hanula has been taking weekly samples of the pest from research kudzu patches to study its biology.

He and Forest Service entomologist Scott Horn tested a variety of colored traps to attract the bug and found it is not attracted to red, purple or black; it favors white most and yellow to some degree. This explains the hundreds of calls UGA Cooperative Extension agents receive from owners of white homes or cars.

To determine how the pest damages kudzu, Hanula harvests the stems and leaves of infested kudzu patches and compares them to the patches he sprayed to protect them from the kudzu bug.

“The pest caused a 33 percent reduction in kudzu growth after one year,” he said. “…we will monitor for several more years to see if the trend continues.”

The Forest Service and UGA scientists hope continual feeding by the pest will deplete kudzu roots and weaken the plants.

“If the bug’s effect is cumulative, kudzu plants will likely weaken, and patches won’t be as thick,” Hanula said. “Hopefully, the bug will reduce kudzu’s ability to climb, which would be good for forestry.”

Much of the land now covered by kudzu is ideal for growing trees, so anything that slows kudzu growth is good for forestry, he said.

Kudzu bugs dining on kudzu may sound like a reason to celebrate; the flipside is that the kudzu bug also loves to feed on soybean plants and other legumes. Georgia farmers grow soybeans for the oilseed and animal feed markets.

UGA entomologist Phillip Roberts has seen the pest reduce soybean crop yield by 19 percent in untreated fields. On a positive note, the bug does not feed on soybean pods.

The kudzu bug was first spotted in Georgia in the fall of 2009 when insect samples were sent to the UGA Homeowner Insect and Weed Diagnostic Laboratory in Griffin. The first samples came from UGA Cooperative Extension agents in Barrow, Gwinnett and Jackson counties.

“As of now, the bug has been reported in 154 of Georgia’s 159 counties—only five along the coast remain unconfirmed,” said Wayne Gardner, a Griffin-based UGA entomologist who has been studying the pest since it was found in Georgia.

The kudzu bug also has been found in all 47 South Carolina counties, 73 North Carolina counties, 25 Alabama counties, two Virginia counties, four Tennessee counties and six Florida counties, he said.

“I think that’s 312 counties in seven states, which is a total land area of 147,342 square miles,” Gardner said.

For tips on controlling kudzu or the kudzu bug, see www.caes.uga.edu/publications/ and search for kudzu or kudzu bug.

Fungus Tapped to Take on Kudzu

By Jan Suszkiw
July 16, 2009

Kudzu, "The Vine that Ate the South," could meet its match in a naturally occurring fungus that Agricultural Research Service (ARS) scientists have formulated as a biologically based herbicide.

By one estimate, kudzu spreads at the rate of 150,000 acres annually, easily outpacing the use of herbicide spraying and mowing, as well increasing the costs of these controls by $6 million annually.

But in Stoneville, Miss., ARS plant pathologist Doug Boyette and colleagues are testing a fungus named Myrothecium verrucaria, which infects kudzu with an astonishing speed of its own. In fact, the fungus works so quickly that kudzu plants sprayed with it in the morning start showing signs of damage by mid-afternoon, according to Boyette, with the ARS Southern Weed Science Research Unit in Stoneville.

He first began working with M. verrucaria in 1998, when a Louisiana Tech University scientist furnished him with isolates from diseased sicklepod specimens. In greenhouse experiments, spray formulations killed 100 percent of kudzu seedlings and 90 to 100 percent of older plants in outdoor trials. Myrothecium also worked its anti-kudzu magic under a wide range of conditions, including the absence of dew.

Additionally, host-range tests in 2005 showed that Myrothecium caused little or no injury to many of the woody plants known to occur in kudzu-infested habitats, including oak, cedar, pine, hickory, pecan, sassafras and blackberry.

A few companies expressed interest, but only if the fungus' production of toxins called trichothecenes could be reduced or stopped. Boyette's group examined several approaches, settling on a method of growing Myrothecium in a fermenter on a liquid diet instead of a solid one. Not only did this stop trichothecene production or reduce it to acceptable levels, the method also extended the fungus' shelf life and potency under field conditions.

Besides kudzu, Myrothecium also showed potential as a pre-emergence bioherbicide, controlling purslane and spurge in transplanted tomatoes.

Read more about the research in the July 2009 issue of Agricultural Research magazine.