How fast has the so-called “kudzu bug” moved across the Southeast over the past two years? Since arriving in the Western Hemisphere by way of Atlanta from Asia in 2009, the insect has spread from nine Georgia counties to across at least 230 counties in four states.
It’s now found in all 46 South Carolina counties, more than 140 counties in Georgia, more than 40 North Carolina counties, along with parts of Alabama, and entomologists have been astounded by its rapid movement, according to Southeast Farm Press.
The bugs, known in most parts of the world as bean plataspids, look like boxy brown ladybugs and emit a foul-smelling secretion when threatened. As a result, it’s often as easy to locate them by smell as by sight when they occur in large numbers.
While they are known to eat kudzu, they can also ravage soybeans, along with other legumes, according to the University of Georgia Cooperative Extension.
Clemson University Entomologist Jeremy Greene says the insects, often mistakenly referred to as stink bugs, are becoming a bigger problem in agriculture as they spread throughout the region.
Landrum Weathers, a farmer in Bowman, told Southeast Farm Press that kudzu bugs got into his soybeans while the crop was still immature. Killing them was no problem, he says, but they kept coming back in bigger numbers after every spray.
“The big problem with kudzu bugs in soybeans is getting insecticide to them,” according to the publication. “They tend to feed on the stems of leaves in the lower parts of the plant and once the soybean canopy covers the rows, it becomes a challenge to get enough chemical to the insects to manage high populations.”
Adults and nymphs gather in large groups and suck sap from a host plant, weakening and stunting it. Adults have been observed sucking sap from the host plant’s leaves, stems, budding flowers and mature green pods. Severe infestations of adults and nymphs feeding on leaf sap can cause extensive defoliation in host plants, it added.
Greene contends the kudzu bug rapid movement may be tied to prevailing weather patterns, which have spread the insect mostly north and east from the epicenter of its starting point.
The insect, about the size of pencil eraser, is greenish brown and round with a wide posterior. It possesses excellent flying skills which helps account for its rapid spread across the Southeast.
“Kudzu bugs have proven to be susceptible to a wide range of insecticides, but Greene explains the problem is exactly what Weathers and other growers in South Carolina are finding that late in the season, killing them isn’t the problem, getting the insecticide to the bugs is the problem,” according to Southeast Farm Press.
“These bugs are very specific on where they feed on soybeans. They occupy the bottom part of the canopy and feed on the stems and leaf petioles. More mature bugs are often found on the main stem of the soybean plant – very near the ground,” Greene says.
There isn’t much a grower can do to protect late-season beans from these insects. “And, with all the wild hosts available around our soybean fields, there isn’t really much they can do in planning for the 2012 season to reduce pressure from kudzu bugs,” he adds.
A part of the control strategy will likely be to knock populations down as early in the season as possible. “We have seen that well-timed insecticide applications can slow down, if not prevent large buildups of these insects later in the season when it becomes more difficult to get material through the plant to the bug,” Greene says.
One tool Greene is working on with colleagues in Mississippi is a biological control of kudzu bugs. There is a native parasitoid that is very specific to the kudzu bug. Kudzu bugs have a number of commonly occurring natural enemies in Asia that may one day be a big part of our control efforts, he says.