Some insects are pests because they bite, sting, carry diseases, or damage food that we want to eat. Other insects are not really pests, just nuisances. The boxelder bug is a good example of a nuisance insect. If you're tempted to reach for a spray can because there are lots of boxelder bugs flying around your house, remember that some straightforward pesticide-free steps can encourage them not to congregate in or around your home.

Identifying Boxelder Bugs

Boxelder bugs are brownish-black and about 1/2 inch long. They have three red lines just behind their head. Their abdomen is also bright red. Young boxelder bugs are mostly red and more oval than the adults.(1)

There are two kinds of boxelder bugs in the U.S. The western one is found west of Nevada, while the other species is found in the East.(1)

Recommendations for managing both kinds of boxelder bugs are the same, so you don't need to try to figure out which kind is in your yard. 

The western boxelder bug is less of a nuisance than the eastern one.(1)

Life History and Habits

Boxelder bugs spend the winter in protected places, including homes. On warm days,  they'llcome out and rest in the sun, and yyou'llsee them on the south and west sides of your house.(2) They do not breed indoors.(3)

In the spring they become active outdoors, and lay their eggs near the seeds of boxelders or other maple trees. The immature bugs feed mostly on these seeds,(1) and the adults feed mostly on the leaves, flowers and seeds.(2) There are usually two generations during the summer.(1)

After the first frost in the fall, adults move to their winter shelter.(2) They can travel several miles looking for winter shelter.(4)

What Kinds of Damage Do Boxelder Bugs Cause?

There are many kinds of damage that boxelder bugs do not cause. They do not cause much damage to ornamental landscape plants, and rarely cause significant damage to fruit trees. They do not injure people or pets.(2) They will not feed on house plants or on your furniture.(3) They don't cause structural damage to your home.(5)

However, boxelder bug excrement can stain curtains, furniture, or clothing, and they give off an offensive odor when they're crushed.(2)

Keeping Boxelder Bugs Out

If boxelder bugs are a problem inside your house, you should make it hard for them to find a way to get inside. Repair window or door screens that are torn.(2) You should also screen crawl space openings, vents, and louvers. Caulk cracks around windows, doors,(2) vents, light fixtures, pipes, conduits, and air conditioners.(4) Attaching weather-stripping or “sweep strips” to the bottom of your doors will help too.(3) (If this all sounds like a lot of work, remember that you'll also be keeping other pest insects out of your house as well.(3)) Boxelder bugs are attracted to light, so don't leave doors or windows open when your lights are on.(6)

Make Your House Unattractive to Boxelder Bugs

To Boxelder bugs often like to spend the winter under rocks, boards, and other debris; in cracks and crevices in walls; in casings around windows and doors; in and around building foundations; and inside houses.(2) They seem to particularly like rough surfaces, two-story houses, and houses close to large trees.(5) Here's how you can make your house less inviting:

• Move any piles of rocks, boards, leaves, or general debris that are near your house.(2)
• Rake leaves and remove unnecessary weeds and grass from a strip between six and ten feet wide around your foundation. If you don't want to do this all the way around your house, focus on the south and west sides.(2)
• Sweep or vacuum up boxelder and maple seeds. A shop vacuum works well on driveways and patios. It can also pick up seeds from your lawn.(2)
• Don't plant female boxelder trees near your house. You can plant male trees, as they are not attractive to boxelder bugs. Remember that because of the distances boxelder bugs can fly, your neighbors’ trees may be the source of your problem.(4) Some towns have ordinances prohibiting planting these trees.(7) You can also consider removing existing trees, if your problem warrants it.(2)

Getting Rid of Boxelder Bugs inside Your House

Three methods are recommended for removing boxelder bugs from your house: hand collecting,(2) sweeping,(8) and vacuuming.(3) If you collect them by hand, you can toss them outside.(9) Boxelder bugs can also be drowned.(2)

Be gentle, suggests University of Idaho extension entomologist Bob Stoltz; “if you mash them, they could stain the wall or carpet red.”(9)

Getting Rid of Boxelder Bugs in Your Yard

If you find boxelder bugs on walls or tree trunks and want to get rid of them, try using your garden hose. A forceful stream of water will wash them off and drown them.(2)

You can also use boiling water to kill clusters of boxelder bugs. Remember boiling water can kill grass in your lawn or other desirable plants, so you need to be careful when you're using this technique.(10)

Using Pesticides to Kill Boxelder Bugs

“Chemical controls are largely ineffective and unwarranted for this nuisance pest,”(4) according to University of Vermont Extension.

Other extension services from around the country agree. Colorado State University Cooperative Extension describes household sprays as “temporary relief only.”(11) “Insecticide sprays are generally not recommended for boxelder bug management,”(2) writes the University of California Cooperative Extension. “They are often no more effective than vacuuming or hosing and repeated applications may be required.”(2)

Conclusion

“Bear in mind that as bad as they are box elder bugs will only be around until the weather gets cold—so the best solution may be to ignore them until they go away,”(5) wrote Oregon State University extension entomologist Jack DeAngelis.
Living with boxelder bugs may be the easiest and simplest solution you'll find. If you've got more of these bugs than you can comfortably live with, try the pesticide-free techniques outlined in this article. 

References

1.    Cranshaw, W. 2004. Garden insects of North America: The ultimate guide to backyard bugs. Princeton NJ: Princeton Univ. Press. p. 230.
 2.    Univ. of California. Agriculture and Natural Resources. 2004. Boxelder bug. Pest Notes Publ. 74114. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74114.html.
 3.     Montana State Univ. Extension Service. 2001. Boxelder bugs. http://Scarab.msu.montana.edu/YardGarden/docs/boxelderbugs-insect.htm.
 4.    Univ. of Vermont Extension. 2003. Boxelder bug: Boisea trivittata (Say). http://www.uvm.edu/extension/publications/el/el259.pdf.
 5.    Oregon State Univ. Extension. Undated. Urban entomology notes: Box elder bugs. www.ent.orst.edu/urban/PDF%20Files/Box%20Elder%20Bug.pdf.
 6.    University of Rhode Island Coop. Extension. Undated. University of Rhode Island GreenShare factsheets: Boxelder bug. http://www.uri.edu/ce/factsheets/prints/boxelderbug.html.
 7.    Univ. of Idaho Coop. Extension. 1999. Just the facts–sheet. Insects and pest information. Topic: Boxelder bugs. http://extension.ag.uidaho.edu/district4/MG/boxelder.html.
 8.    Univ. of Washington Coop. Extension. 1996. Western boxelder bug. Publ. EB1154.
 9.    Univ. of Idaho Coop. Extension. 1999. HomeWise: For release the week of March 15, 1999. http://info.ag.uidaho.edu/homewise/homewise_031599.htm.
10.    Ohio State Univ. Extension. Undated. Ohio State University Extension fact sheet. Entomology: Boxelder bug. http://ohioline.osu.edu/hyg-fact/2000/2106.html.
11.    Colorado State Univ. Coop. Extension. 2004. Boxelder bugs. http://www.ext.colostate.edu/pubs/insect/05522.html.