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.

Pyrethroid label requirements tweaked again

Last year I posted a story about the new pyrethroid insecticide label requirements being sent to pesticide manufacturers by the U.S. Environmental Protection Agency. The requirements were designed in 2009 to reduce the risk of drift (wind carried contamination) and runoff (stormwater-carried contamination) of these commonly used insecticides. Since last spring, when pesticide manufacturers were officially informed of the new standards, the EPA has continued to dialog with both regulators and the pest control industry.  The results of this dialog are now out, and the final product is a big improvement, in my opinion.

The new EPA label requirements will
continue to allow pyrethroid applications
to eaves and protected sites around homes
where mosquitoes and other pests
may be resting.

At issue were applications needed to control certain overwintering insects like brown marmorated stink bug and kudzu bug, both of which aggregate on the sides and eaves of structures prior to entering the home or other building.  Under the 2009 rules, outdoor applications to the sides of structures were limited to crack and crevice applications or building foundations up to a height of three feet only.  In addition, all outdoor applications to impervious surfaces such as sidewalks, driveways, patios, porches and structural surfaces (such as windows, doors, and eaves) were to be limited to spot and crack-and-crevice applications, only.

After consultation with the National Pest Management Association (NPMA), the Association of Structural Pest Control Regulatory Officials (ASPCRO) and the State FIFRA Issues Research and Evaluation Group (an EPA advisory group also comprised of regulatory officials), the EPA agreed to make further changes to the original label requirements to allow for better control of overwintering insects.

While restrictions on insecticide applications to impervious surfaces and prior to expected rainfall have not changed, there are some big changes on applications to structures, as published in a January 10 letter to pesticide manufacturers.  The three changes are summarized as follows:

• Now applications of pyrethroids may be made to the exterior of buildings where the treated surfaces are underneath eaves, soffits, windows or doors that are protected by coverings, overhangs, awnings or other structures that protect the residues from rainfall;
• application bands up to one inch-wide may be applied to cracks or other potential pest entry points;
• and applications may be made using a coarse, low-pressure spray to portions of surfaces that are directly above bare soil, lawn, mulch or other vegetation.

The purpose of these requirements is to prevent pyrethroid pesticides from entering storm water and getting into streams, something that is most likely when pyrethroid sprays land on impervious surfaces like asphalt or concrete.

In addition to giving back to PMPs the ability to use pyrethroids against overwintering pests these new regulations should help applicators control nuisance and public health mosquitoes that frequently rest on the sides of buildings and around doorways.  This was, in my view, a potentially serious public health issue with the 2009 rules.

So what will be the big change to the way your company applies pyrethroids after the dust is all settled? The new labels will prohibit power spraying driveways and over sidewalks, garage doors and any vertical building surfaces over pavement. Assuming the manufacturers follow these guidelines closely, labels should allow low-pressure sprays to the sides of structures over vegetation or soil and in sites protected from the rain, in addition to cracks and crevices.

Congratulations to the EPA and to those regulators and NPMA experts who took the time to look for ways to keep the pyrethroid label requirements reasonable while continuing to protect the environment. This is one of those examples of how the system sometimes works in everyone's favor--except, in this case, the pests'.