It's a bright October afternoon and the white siding on the sunny side of your house is speckled with hundreds of small, squarish, olive-brown bugs. More are landing on the window trim and the garage door. Brush one off your sleeve and your fingers smell bad for an hour. Those are kudzu bugs, and they're shopping for a place to spend the winter.
Kudzu bugs (Megacopta cribraria) swarm siding in fall because they're looking for cracks and wall voids to spend the winter in, and they're drawn to light-colored surfaces, especially white. They don't bite or damage the house, but they stink and stain when crushed. Keep them out by sealing gaps and screening vents before fall, and vacuum the ones that get inside instead of crushing them.
What Are Kudzu Bugs?
The kudzu bug, Megacopta cribraria, also goes by bean plataspid. Clemson's Home & Garden Information Center is blunt about the most common mistake: it isn't a beetle. It's a true bug, closer kin to stink bugs, with piercing-sucking mouthparts it uses to drink plant sap.
Adults run about 4 to 6 millimeters, roughly a quarter inch, per NC State Extension. From above they look nearly square. Color is light brown to olive green with fine brown speckling. The young (nymphs) are smaller, the same general shape, and noticeably hairy.
Clemson reports the first U.S. detection in northeastern Georgia in October 2009. NC State tracked them to more than 60 Georgia counties and into Macon County, North Carolina, by 2010, and later confirmed them in 18 states. NC State also puts one rumor to rest: they were not released on purpose to fight kudzu. Their best guess is the bug hitchhiked in on a commercial flight.
Why Do Kudzu Bugs Swarm Your House in Fall?
Clemson describes two generations a year in the Southeast. The first develops mostly on kudzu or wisteria. The second moves onto soybeans and other bean-family plants, and NC State notes that shift into soybean fields happens in July and August.
By fall those host plants are fading, and the adults go looking for shelter. In the wild that means leaf litter, loose tree bark and mulch. Around a house it means cracks, crevices and wall voids. NC State says they gather on light-colored siding and fascia boards first, then work their way in through gaps under siding, around doors and windows, and around plumbing and air-conditioning penetrations.
Clemson says they prefer light-colored houses, and white in particular. N.C. Cooperative Extension's Pender County center adds that they'll coat tree trunks and light-colored cars too. The usual landing spots on a house:
- Window trim and door frames
- Gutters and fascia
- The sunniest, brightest walls
- Gaps where siding overlaps or meets the foundation
Location sets the odds. Homes next to soybean fields or kudzu patches get hit hardest, according to NC State. That's a familiar picture on the edges of Greenville, Spartanburg, Columbia and the Triangle, where kudzu blankets roadside banks and wood lines. But kudzu bugs are strong fliers, so a house a few lots away from the nearest patch can still draw a crowd.
Are Kudzu Bugs Harmful?
To your house, no. The Pender County extension office states plainly that they won't damage your house or harm you if you touch one. They feed only on plant sap, mostly from bean-family plants, so there's nothing inside your home for them to eat.
They're still unpleasant. Their body fluid smells foul and, per Clemson, can stain fabric and wall coverings. Handle them with bare hands and the secretion can stain your skin, and Clemson notes that in some sensitive people it causes blistering and moderate discomfort. If a reaction on your skin worsens or doesn't clear up, have a doctor look at it.
One more catch: if a lot of them die inside a wall or attic, Clemson warns the dead bugs can smell as they break down and can attract secondary pests such as carpet beetles and ants. Clean up the dead ones you can reach.
Kudzu Bug, Lady Beetle or Stink Bug?
Three different insects pile onto Carolina and Virginia siding in the fall, and the fix for each is similar, but it helps to know which one you've got.
| Kudzu bug | Asian lady beetle | Brown marmorated stink bug | |
|---|---|---|---|
| Shape | Squat, nearly square | Rounded dome | Wide shield |
| Color | Olive to light brown, speckled | Orange to red, usually spotted | Mottled gray-brown |
| Type | True bug | Beetle | True bug |
| Size | About 1/4 inch | Similar to a kudzu bug | Noticeably larger |
If your bugs are orange or gray rather than olive, our guide to stink bugs, lady beetles and cluster flies in fall covers those. And if the swarm on your sunny wall is made of tiny red specks smaller than a pinhead, that's a different animal entirely: see how to get rid of clover mites.
How to Keep Kudzu Bugs Out of Your House
Exclusion is the real fix, and timing is everything. Do this work in late summer, before the fall flights start.
- Seal the gaps. Caulk cracks around window and door trim, and seal around plumbing lines, AC lines and cable entries. NC State calls sealing the long-term answer.
- Screen the vents. Clemson specifically mentions soffit vents and peak (gable) vents, along with window and door screens.
- Fix doors. Worn door sweeps and weatherstripping are open invitations.
- Cut back host plants. Clemson suggests cutting back kudzu and removing wisteria near the house before fall. NC State is realistic about it: the patch may be on a neighbor's land, and since the bugs fly, clearing it may not solve the problem on its own.
Our fall pest-proofing checklist walks through the same sealing work room by room, and it keeps out mice, spiders and roaches too.
What If They're Already Inside?
Don't swat them and don't crush them. That's how you get the smell and the stains.
Vacuum them instead. Clemson recommends a shop vacuum, because the odor can hang around in a regular household vacuum, with 1 to 2 tablespoons of dish soap per gallon of water in the canister to kill them. Dump the soapy water afterward. With a bagged vacuum, NC State suggests sealing the bag inside a trash bag and freezing it for several days, or simply dropping the bugs into soapy water. Don't toss them out the door alive. NC State notes they tend to survive nearby and come right back.
What about spraying the siding? NC State is skeptical of do-it-yourself exterior treatment: homeowners usually can't reach the high spots, applications may need repeating as often as weekly, and many products no longer allow broadcast spraying of exterior surfaces. Runoff from hard surfaces can wash into storm drains. The Pender County office adds that spraying siding only deters them for a while. Our post on where pest control actually sprays around a house explains why label rules keep treatments narrow.
Are Kudzu Bug Numbers Going Down?
In many places, yes. In 2017 University of Georgia researchers reported a significant drop in Georgia kudzu bug numbers over the previous three years. They credited two natural enemies. One is a tiny parasitoid wasp, Paratelenomus saccharalis, which lays its egg inside a kudzu bug egg; UGA observed more than 50 percent kudzu bug mortality from it in some soybean and kudzu fields. The other is Beauveria bassiana, a fungus that kills both young and adult kudzu bugs.
That doesn't mean they're gone. A house beside a big kudzu bank can still get a heavy fall landing, and the bugs that overwinter in your walls will come back out in spring as they head back to kudzu and wisteria.
When to Call a Professional
- They come back every fall in large numbers despite your sealing
- The problem spots are high up: soffits, gables, the roofline
- Bugs keep turning up in living spaces from the attic or wall voids
- You can't tell what's on the siding, or you have more than one overwintering pest
Clemson itself recommends a pest management professional when kudzu bug numbers are very high and keep reinvading. Our residential pest control team can inspect the outside of your home, find the gaps they're using and target the areas where they gather. Request a free quote and we'll take a look.
Key Takeaways
- They're true bugs, not beetles. Kudzu bugs are stink bug relatives, about a quarter inch long and nearly square.
- Fall swarms are a search for winter shelter. Light-colored siding, especially white, draws them in, and homes near kudzu or soybean fields get the most.
- Harmless to the house, hard on noses. They don't damage anything, but they stink, stain, and can irritate sensitive skin.
- Seal and screen before fall. Caulk gaps, screen soffit and gable vents, fix door sweeps.
- Vacuum, never crush. A shop vac with soapy water handles indoor stragglers without the smell.
Sources: E. P. Benson and J. Greene, "Kudzu Bugs Around the Home" (HGIC 2430), Clemson Cooperative Extension Home & Garden Information Center; M. Waldvogel, P. Alder and C. Hayes, "Kudzu Bugs: A Nuisance and Agricultural Pest", NC State Extension; C. Glen, "What Can I Do About Kudzu Bugs?", N.C. Cooperative Extension, Pender County Center; C. Thompson, "Kudzu bugs' decline is attributed to two factors", University of Georgia CAES Field Report.
Frequently Asked Questions
No. Kudzu bugs feed on plant sap with piercing mouthparts, mostly from kudzu, soybeans and other bean-family plants. N.C. Cooperative Extension says they won't harm you if you come in contact with them, though handling them can stain skin and irritate it in some sensitive people.
They're looking for a sheltered place to spend the winter. In fall they leave fading kudzu and soybean plants and gather on light-colored surfaces, especially white siding, then crawl into gaps under siding and around windows, doors and pipes.
No. They don't eat wood or damage the structure. The problems are the foul smell they release and the stains they leave on fabric and walls when crushed. Large numbers dying inside a wall can also smell and attract carpet beetles and ants.
Vacuum them instead of crushing them. Clemson recommends a shop vacuum with 1 to 2 tablespoons of dish soap per gallon of water in the canister. If you use a bagged vacuum, seal the bag in a trash bag and throw it out.
Their host plants (kudzu, wisteria, soybeans and other beans) and, in fall, light-colored surfaces. Clemson says they prefer light-colored houses, especially white ones, and gather on window trim, door frames, gutters and sunny walls.
Those sheltering in your walls leave in spring and head back to kudzu and wisteria. Populations have also dropped in many areas since University of Georgia researchers documented a parasitoid wasp and a fungus killing them, but homes beside kudzu or soybean fields can still see fall swarms.
Neither. A kudzu bug is a true bug in the same broad group as stink bugs, but a different species. It's about the size of a lady beetle, but lady beetles are true beetles and are usually orange with spots, while kudzu bugs are olive-brown and nearly square.
Photo credits: Judy Gallagher, CC BY 2.0, via Wikimedia Commons; NCBioTeacher, CC0, via Wikimedia Commons; Alandmanson, CC BY 4.0, via Wikimedia Commons.