Kudzu bug: A new Texas pest... or not?

Kudzu bug has a unique ovoid shape. The wings
are hidden under a shield-like scutellum, making
it look more like a beetle than a true bug. Photo
by Dan Suiter, University of Georgia.  

In October 2009, millions of small, pill-like bugs startled homeowners across nine counties in northeast Georgia. The never-before-seen insects covered the sides of homes by the thousands, and concerned citizens began calling Extension offices daily. Though puzzled at first, entomologists eventually identified the insect as "kudzu bug", an exotic insect never before seen in the U.S.

The kudzu bug, Megacopta cribraria, is native to Asia, where it is widely distributed. As its name implies, its preferred host plant is the invasive weed, kudzu.  No one knows how it got here, but like many invasive pests it made itself at home quickly.  Highly mobile, within a year the kudzu bug had spread to 60 north and central Georgia counties.  Two years later every county in the state had them.

Last week Texas became the 14th state with verified populations of kudzu bug.  Sharp-eyed county Extension agent Kim Benton reported kudzu bugs from a home garden in Rusk, TX, south of Tyler. The bugs were clustered on eggplant and other vegetables before being transplanted into the garden.

Description and damage

It is hard to mistake kudzu bug for anything else.  The bug is beetle-like in appearance with a unique, four-sided, ovoid shape.  It is greenish-brown and shiny, up to 1/4 inch-long (3.5-6 mm).  It uses its piercing/sucking mouthparts to feeding on the sap of kudzu and other legumes.

For soybean farmers and vegetable growers kudzu bug is another pest to battle. The bugs overwinter close to kudzu, their favorite food in the spring.  But in summer they move into soybeans where they can cause significant yield reductions. To a lesser extent they feed and reproduce on sweet peas, snap beans, cowpeas, lima beans and wisteria.  It may be seen on other plants as well, where it gathers temporarily, usually to move on in a day or so.

Is it a good bug?

Anyone familiar with the weed kudzu will be excused for thinking that having kudzu bug might be a good thing.  After all, one of the reasons kudzu is such a horrible weed is that few things eat it.  Wouldn't it be good to have an insect to keep kudzu in its place?

That's what the good folks in Georgia hoped.  But according to Georgia extension entomologist Phillip Roberts, their optimism didn't last.  "The first years we saw what we thought was a lessening of the kudzu problem.  Other weeds seemed to be competing more effectively with the kudzu."  But after a year, he said, the kudzu seemed unfazed.  "There has not been any noticeable decline in kudzu growth since the beetle moved in."

A (minor) crossover pest

Kudzu bugs cover the eave of a home in Georgia. Photo by
Dan Suiter.

Kudzu bug is one of very few agricultural pests that are structural pests as well. Problems in Georgia with kudzu bug are mostly restricted to homes near kudzu patches and soybean fields (rare) in Texas.  According to Georgia extension entomologist Dan Suiter, unlike the multicolored Asian lady beetle, kudzu bugs are attracted to buildings in the fall but rarely come indoors. "We never really see them getting inside," he said.

Nevertheless, expect that some homeowners will be upset over thousands of bugs clustering on the outside of their homes, especially on white-painted gutters, siding and around windows. Also, the bugs have an odor and secrete a staining fluid when disturbed.

Kudzu bug activity around structures is most noticeable in the fall.  This is when bugs from nearby kudzu are seeking shelter and are attracted to homes. 

How bad?

It's yet to be seen whether kudzu bug will become a noticeable pest in Texas, but indications from Georgia suggest it will not be a serious long-term pest.  Because kudzu is less prevalent in Texas than Georgia and other southern states, the bug is likely to occur only in east Texas, and populations limited to start with. But at least two egg parasitiods (egg predators) and a fungus called Beauveria bassiana, have severely reduced the kudzu bug problem in Georgia and most southern states. After being overwhelmed with calls the first five year after the bug's discovery, today Suiter says he "doesn't see more than 20 bugs a year" brought into his office.

Vegetable gardeners in counties with kudzu may be more bothered. Edamame, peas or other beans are susceptible to these bugs and may require treatment.

Control

If you are called on to manage kudzu bugs around a home, here are a few tips:

• Focus on the outside of the building when controlling kudzu bugs--few bugs will be indoors, though caulking and sealing will also help in that regard.  
• Pyrethroid insecticides are generally effective against kudzu bugs.  Bifenthrin and lambda-cyhalothrin are especially good in crop situations, according to Roberts.  Suiter said his research shows Alpine WSG (dinotefuran) also works well and has the added advantage of quickly killing the bugs, in seconds, eliminating the chance for unsightly aggregations to occur. 
• Look for, and treat, any crack or crevice where bugs are aggregating. Examples include: gaps behind siding and around windows and doors; high places (such as around soffits, fascia boards and gutters); even loose bark on nearby trees.
• If kudzu is present outside the home, use a herbicide to remove it, preferably during the spring or summer.  This can help reduce the numbers of bugs coming to the outside of the home in the fall.

If you find what you believe are kudzu bugs we would love to see a clear photo.  Also save specimens to bring to your county Extension office for official confirmation.  This can help us track the spread of kudzu bug within the state.

"If Kudzu wasn't bad enough"...and other thoughts on exotic pests

Dr. Dan Suiter and Lisa Ames with the University of Georgia just sent out a pest alert on an insect called the "bean plataspid". I had never heard of a plataspid (pla TASS pid) before, so I looked in my well-worn copy of "How to Know the True Bugs" by James Alexander Slater--a very useful book for relatives of the box elder bugs--but with no luck. A quick check of the Internet revealed that Plataspids are Old World insects--hence not covered by my U.S. field guide.

Suiter and Ames recently received numerous samples of these insects swarming around homes in Georgia. Homeowners there are being repelled by not only the numbers, but also by a foul smell associated with the bugs. Turns out that this was the first known collection of these insects, known scientifically as Megacopta cribraria in the U.S. It is native to India and China, where it feeds on kudzu.

At this point many Southerners can be heard shouting "Glory be! A bug that eats kudzu! An answer to our prayers!" If you are not from the South, or are unfamiliar with kudzu, it is an invasive plant nightmare. Originally introduced in 1876 at the Centennial Exposition in Philadelphia, Pennsylvania in a Japanese government display garden. Planted widely as an ornamental vine for its abundant vegetation and sweet-smelling flowers, it was promoted as a forage plant by the Soil Conservation Service in the 1920s and 30s for erosion control. Bad idea. Kudzu smother trees and other plants under a solid blanket of leaves, by girdling woody stems and tree trunks, and by breaking branches or uprooting entire trees and shrubs through the sheer force of its weight. It grows at a rate of up to a foot a day.

Unfortunately for us, the bean plataspid does not appear to be a good solution to kudzu. Besides being a household pest on the order of the box elder bug or the Asian mulicolored lady beetle, the bean plataspid is a pest of numerous legume crops, including soybeans. The University of Georgia, Georgia Department of Agriculture, and U.S. Department of Agriculture consider it a potential agricultural pest and are partnering to take some regulatory action.

This appears to be the latest assault against the native fauna in our country. It's bad enough to have a new structural pest stinking up our homes, but when a foreign insect crosses the border into the U.S. it's generally forever. The fire ant landed on the sandy bay shores of Mobile, Alabama about 80 years ago and forever altered the ecology of the southern pine forest to the Texas prairies. We still don't know the full impact of fire ants on native wildlife and plant life, not to mention the American economy.

Last week I attended a conference on invasive pests, put on by the Texas Invasive Plant and Pest Council, in San Antonio. If there was ever a more discouraging subject for a biologist, I don't know what it is. In one of the talks, a botanist talked about his efforts to catalog and classify all the invasive foreign plants in Texas. He proposed classifying certain plants as some pests as "super watch" plants. "Super watch" plants are those which might possibly be removed from the Texas landscape before they become impossible to control.

I think the concept is a useful one for insects. By classifying certain insects as "Potentially Eradicable" pests, or putting them on some sort of "Super Watch" list, we accept responsibility for going after these pests. It seems to me that under our current system we have little incentive to go after new pests before they can get established.

Take the Formosan termite. We continue to watch helplessly as this pest becomes established in new sites around the South and in Texas. The potential economic impact of the Formosan termite is staggering, as it is at least twice as destructive as our native subterranean termite on homes, and an eater of live trees as well.

Ironically this is one pest that, in my opinion, could be controlled in isolated infestations before it becomes firmly established. We have dozens of sites in Texas where the Formosan termite is established on one or a few home properties. A determined effort to eradicate colonies with termite baits has, in my opinion, a good chance of succeeding in nipping many of these mini-invasions in the bud.

So what does all this have to do with pest management professionals? Knowing where a pest is found and how fast it is spreading is important for decision makers to know whether and how an invasive pest might be eradicated. Suiter and Ames are requesting PMPs in Georgia to report any sightings of the bean plataspid there. Here in Texas we are requesting PMPs to report new sightings of the rasberry crazy ant and the Formosan termite. These reports are very important to us and often form the basis for research dollars to work on solutions for these pests.

I will be working with Drs. Roger Gold and Robert Puckett this year attempting to delineate precisely where Formosan termites are present in the state of Texas. The research is being funded by the Texas Department of Agriculture and USDA's Animal and Plant Health Inspection Service. More information about the project will be forthcoming, but if you know of any suspected Formosan termite infestations we definitely want to know.

If only the Formosan termite could be coaxed into preferring kudzu.