An insect that feeds on the aggressive kudzu plant may sound like the answer to weed-control prayers, but there’s a devilish catch. The kudzu bug, as this non-native insect is called, also feeds on cultivated legumes, such as soybeans, snap beans, lima beans and flat beans.
“It’s a shame it moves over to so many other hosts,” says Greg Hodges, Florida Division of Plant Industry bureau chief for pest diagnostics, in Gainesville.
The bug, sometimes referred to as the bean plataspid, also has been found to reproduce on wisteria, a genus of leguminous landscape plants considered weeds by many, says Wayne Gardner, an entomology professor at the University of Georgia in Griffin.
“We’re getting a lot of reports on wisteria and of [the kudzu bug] surviving really well on it,” he says.
In addition, the kudzu bug has been found on eggplant and corn, although those crops probably won’t support reproductive populations, says Stormy Sparks, an entomology professor at the University of Georgia in Tifton.
“It’s attracted to vertical surfaces,” Sparks says. “Corn’s not a host, and that’s probably what’s happening with the eggplant. It’s probably in the area where beans are planted. That’s what I’m hoping.”
Whether the pest feeds on peanuts, another legume, remains unknown, Sparks says, adding the host range is just one of many questions that researchers hope to answer in the coming months.
“I don’t think peanuts look all that promising [as a host], which is good news,” he says. “But it’s a legume, so it’s something we’re still keeping an eye on.”
An Asian native
The kudzu bug, also dubbed the globular stink bug or lablab bug, is native to Asia, the Indian subcontinent and Australia. In Asia, it is a pest of economic concern.
It was first confirmed in the United States in Barrow County, Ga., in 2009.
Known scientifically as Megacopta cribraria, the pest has since spread and is currently found throughout all of South Carolina; much of Georgia and North Carolina; seven to eight counties in Alabama; and the Blue Ridge Mountain area of Virginia, Gardner says.
Immature kudzu bugs have been found in pick-up truck beds, suggesting they may be expanding their range through hitchhiking, Hodges says.
Kudzu bugs have yet to be confirmed in Florida, although they’ve has been found in the extreme northern portion of neighboring Ware County, Ga.
Be on the lookout
The kudzu bug is about the size of a pea, is metallic brown and has a broad butt. It is closely related to stink bugs and will emit an offensive odor if annoyed or squished.
Like other true bugs, kudzu bugs insert straw-like stylets into plants to suck out the phloem—the plant’s nutrient-carrying liquid.
Most of what entomologists know about the kudzu bugs’ habits in this country is based on observations and on field trials in soybeans.
As a result of feeding on stems and leaves, soybean plants are weakened, causing wilt, defoliation, reduced pod set and reduced bean size. It doesn’t appear to feed on bean pods.
“What we’re generally seeing is they like to feed on the stems,” Gardner says. “If they’re on the leaves, I think they’re feeding on the veins of the leaves.”
Last year in untreated Georgia soybean fields, kudzu bugs caused 10 percent to 30 percent yield reductions, Sparks says.
“And they’re running into populations that are higher than they were last year,” he says. “One of my big concerns is contamination at harvest.”
The good news is that several registered pesticides, including pyrethroids, control the pest, Sparks says.
Pests on the move
One of the challenges is the pest’s migratory nature, Gardner says. You can treat your fields, significantly reducing populations.
But adults simply move in from untreated adjacent kudzu and reinfest your crop.
As the kudzu begins to senesce and die off in October, kudzu bugs seek overwintering shelter in large groups. This can include under tree bark, in wood piles, in plant litter in fields and in houses, Gardner says.
In fact, homeowners in northeast Atlanta first brought the pest to entomologists’ attention in 2009, he says.
“Homeowners were complaining about these bugs all over their houses,” he says.
When the kudzu begins to sprout in spring, kudzu bugs emerge from overwintering and begin laying eggs, starting the cycle again.
Kudzu bug added to survey list
Surveyors who are part of the national Cooperative Agricultural Pest Survey have added the kudzu bug to their list of pests to watch for when they’re out in the field, Hodges says.
In addition, DPI and the University of Florida twice a year conduct a joint pest videoconference to exchange information and update each other on the latest findings.
The kudzu bug was on the agenda of a video exchange held in mid-September.
Gregg Nuessly, an entomology professor and assistant director of the Everglades Research and Education Center in Belle Glade, Fla., says he’s concerned about the pest because of the state’s large snap bean industry.
“Last year and continuing this year, they’re feeding on cultivated legumes, so we’re watching this one,” he says about the kudzu bug.
In Georgia, entomologists have seen it on pole and snap beans in homeowners’ gardens, Gardner says.
But he hasn’t heard any damage reports from snap bean growers in southwest Georgia, where the bulk of the state’s commercial green bean crop is grown.