This week’s warm temperatures have generated lots of kudzu bug calls. The bugs have been with us all winter, but the cold temperatures kept them inactive. Now that we’ve had warm temperatures, the bugs are on the move.
Kudzu bugs emerge from their winter inactivity searching for food. These bugs don’t feed on the leaves of kudzu. They actually feed on the sap. They have a mosquito-like mouth. They insert their needle-like mouth into the stem, then they suck sugary juice from the plant’s vascular tissue.
However, kudzu is not growing right now. So without kudzu to feed on, the bugs are just congregating or massing in groups. Kudzu bugs are attracted to light colors such as light colored t-shirts, light colored trucks, and light colored houses. We have many reports of them congregating on the sunny side of houses.
Last year was the first year we truly had kudzu bugs (Megacopta cribraria) in Caldwell County. These bugs are native to Asia, the same place kudzu comes from. The bugs first appeared in Georgia four years ago. Since then, they have spread like their namesake, kudzu, and are now endemic in Alabama, Tennessee, South Carolina, North Carolina, and Virginia. It appears their range will expand exponentially again this growing season.
These insects feed only on legume plants. Their preferred host is kudzu. It was once thought the first generation of the season needed to dine on kudzu before reproducing. This is now known to be false. Legume plants other than kudzu can sustain these bugs and their reproduction.
If kudzu bugs appear on non-legumes such as figs, magnolias, grapes, etc., they are not feeding, they are just congregating. These bugs only feed on legumes such as green beans, soybeans, kudzu, and wisteria.
For most homeowners, the bugs will become less troublesome as spring progresses. The bugs will move to kudzu once it starts growing, then the bugs will move from kudzu to soybeans in June and July. There are 600 acres of soybeans grown in Caldwell County. Adult kudzu bugs may become pests in the soybean fields as well as some home gardens.
Controlling kudzu bugs is an interesting challenge. Adult kudzu bugs are very mobile, but the nymphs are not. The nymphs are wingless. Any of the contact pyrethroid insecticides (permethrin, bifenthrin, or lambda-cyhalothrin) will control the nymphs. However, adults are more difficult to control because they can fly. This allows the adults to leave the field and reinfest after insecticide applications are made.
For soybean growers, we recommend sampling with a sweep net. One nymph per sweep is the threshold to spray. Waiting until this level is reached (June or July) will preserve crop yields and minimize insecticide applications. Treating adults before the nymphs hatch will kill natural enemies in the bean fields. Without natural predators (spiders and beetles), soybean pests such as spider mites and soybean looper can reproduce unchecked. These pest populations can then require additional insecticide applications.
Last year the Caldwell Extension Center held a special training to help farmers understand this new pest. We also sampled fields to understand the problem. This year homeowners will likely develop a better understanding of kudzu bugs. We will also continue to scout for kudzu bugs this season so we can advise farmers of best management practices for managing kudzu bugs.
The key for homeowners when dealing with kudzu bugs is to vacuum them up if they are in the house. Seal up your home and caulk around windows to keep them from entering the house this fall. And finally, try to remove any kudzu that you can.