Question: How can I get rid of these bugs on my bean plants?
Answer: This invader is known as the bean plataspid, but is more commonly being referred to as the kudzu bug. It feeds on kudzu, wisteria, and other members of the bean family.
Those of you that have encountered this creature may be wondering how it ended up in Sampson County. Well, kudzu bugs are native to China and India and had never been seen in the western hemisphere until the fall of 2009. Lucky for them they landed in one of the largest kudzu patches in the world, which is in Georgia. In just a little over two years these small but highly mobile insects have spread throughout Georgia, South Carolina, and Alabama, and can now be found in most of North Carolina. Their introduction is believed to have been accidental, and could possibly have occurred through the Atlanta airport. It is expected their rapid spread will continue throughout the kudzu infested south. Kudzu, which hails from China and Japan, is considered a highly invasive species in the United States. Though intentionally cultivated for erosion control and animal feed in the early 1900’s, it quickly spread out of control and has since come to be known as “the vine that ate the South.”
At first, the kudzu bug seemed like a good thing since it helps control kudzu. Unfortunately, it is not that simple because they can feed on any member of the bean family. This includes ornamental plants like wisteria, also from Asia and a favorite of the insect, as well as edible crops like peanuts, soybeans, butter beans, green beans, and field peas. For home gardeners it is not yet known how much impact kudzu bugs will have on ornamentals and vegetables. They have been widely reported on wisteria in our area this spring, but it is thought they are just feeding on the wisteria until the kudzu starts growing. If that is the case, and they move on to kudzu in the next few weeks little damage will be done. If they continue to feed on wisteria all season it is more likely they will damage the plants. It is uncertain how much damage they may cause to summer crops of butter beans, green beans, and field peas.
Though they are only known to feed on plants in the bean family, kudzu bugs will congregate in large numbers on many plants as well inside and outside of homes. They are attracted to light colors and have been documented in the thousands covering sides of houses, tree trunks, and even light colored vehicles. During winter they often come indoors by the droves, though this behavior has not yet been observed in our area. They do not cause damage inside the home but are considered a nuisance pest and can be removed with a vacuum cleaner.
Kudzu bugs do not eat plant leaves or stems. Instead they feed on plant sap using their piercing sucking mouthparts, which are shaped like a hypodermic needle. Symptoms caused by heavy feeding include stunting, brown leaf edges, wilting, and dropping of flowers and seedpods. On ornamental plants like wisteria control is usually not necessary unless the insects occur in very large numbers on young plants. Since the insects tend to congregate in large clusters, one of the easiest ways to control them is to knock them off the plant into a bucket of soapy water where they will drown. Spraying pesticides may discourage these bugs temporarily, but does not provide lasting control. Insecticides containing carbaryl, malathion, permethrin, or bifenthrin will kill insects when sprayed, but new kudzu bugs will quickly re-infest plants.
Hopefully this summer these bugs will stay in the kudzu rather than move into home vegetable gardens where they could feed on butter beans, green beans, peanuts, and field peas. Gardeners will need to keep a close eye on their crops this season and contact their local Extension office for control recommendations if they become a problem.
Co-authored by: Charlotte Glen, Horticulture Agent, Pender County
Reminder: A growing program this year is the “Sampson County Friends of Horticulture.” This program offers monthly “How To” Horticultural Seminars. Please call (910) 592-7161 for more information. Please call the Sampson County Cooperative Extension Center at (910) 592-7161 with your horticultural questions and to register for any upcoming events. Be sure to check out the Ask An Expert Widget at sampson.ces.ncsu.edu for any questions you may have.