Accidentally introduced insect shows promise in battle with kudzu
In October 2009, Dan Suiter, an entomologist with the University of Georgia (UGA), noticed large numbers of an unidentified insect in and around kudzu fields in northeast Georgia. This turned out to be the first recorded sighting of the bean plataspid aka “kudzu bug“ (Megacopta cribraria) in North America. That first year saw only nine counties in Georgia infested with the bug; however, by August 2011 almost all of Georgia, South Carolina, and half of North Carolina hosted populations of the new invader.
The bean plataspid, a round brown bug sometimes known as the globular stinkbug, is native to Asia and feeds primarily on legumes such as kudzu and soybean. The bug is considered an agricultural pest in China where it damages soybean plants. Though early observations in Georgia have raised similar concerns, in the United States, the bean plataspid also feeds heavily on kudzu, the well-known invasive plant often referred to as the “vine that ate the South.”
When entomologists Jim Hanula and Scott Horn—both with the Southern Research Station Insects, Diseases, and Invasive Plants unit—heard about the unusually high numbers of the bug on kudzu, they wondered whether this accidentally introduced insect could actually benefit the South by slowing down kudzu. To investigate this question they enlisted the help of Yanzhuo Zhang, a postdoctoral associate at UGA.
The scientists set out to determine the kudzu bug’s biology (life cycle), seasonality (when it was active), host range (what plants it might potentially eat), and impact on kudzu (potential to reduce growth). They discovered that the bean plataspid began laying eggs in early spring as kudzu vines broke dormancy. “Data from traps showed three peaks of adult flight activity, suggesting that there are two generations of the insect per year on kudzu in our area,” says Horn. “We also found that the bug laid more eggs on kudzu than on any other plant species. As expected, soybean was a close second.”
To determine whether or not the bean plataspid impacted kudzu growth the scientists protected some areas of their kudzu sites with insecticides and then compared those to unsprayed areas the same size. “We found that unprotected plots had 40 times the number of bugs than sprayed plots and a third less kudzu,” says Hanula. “We were actually surprised that this insect had such an impact in only one growing season.”
Kudzu covers large areas of potential forest and farm land in the South—approximately 5 to 7 million acres—leading to an estimated $500 million annual loss in potential revenue. The hope is that over time this “kudzu bug” will eat enough leaves and vines to deplete kudzus root reserves and inhibit its ability to spread, a result that would surely be a welcome to the forest landowners, farmers, utility companies, road departments and railroads that routinely deal with this iconic invasive plant.
Read the full text of the article: Zhang, Yanzhuo, James L. Hanula, and Scott Horn. 2012. The biology and preliminary host range of Megacopta cribraria (Heteroptera: Plataspidae) and its impact on kudzu growth. Environmental Entomology. Vol. 41: No. 1, pp. 40-50.