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.