The only permanent fix for boxelder bugs is keeping them out: seal cracks, gaps and screens on the sunny south and west sides of the house before late August, when they start gathering. Bugs already inside can only be vacuumed or swept up; they don’t breed indoors and die within days. Outdoors, soapy water or an insecticide sprayed on clusters in late summer and early fall stops them before they get in. Removing female boxelder trees near the house also helps, but bugs can fly in from blocks away.
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Why Boxelder Bugs Come Inside
Boxelder bugs feed on the seeds of female boxelder trees, and sometimes maple and ash, all summer. In fall they look for somewhere warm to spend winter, and gather in the thousands on sun-warmed walls, especially on the south and west sides and on buildings taller than their neighbors. They crawl into cracks, siding, attics and wall voids, then wander into living spaces on warm days in winter and spring.
They don’t bite (except very rarely), don’t damage the house, and don’t reproduce indoors, but they can stain curtains and walls with droppings and smell when crushed. See boxelder bug pictures and facts.
Step 1: Seal Them Out (the Permanent Fix)
- Do it before late August, before bugs start clustering.
- Repair or replace torn window and door screens.
- Caulk gaps around window and door frames, siding, fascia boards and trim.
- Seal where pipes, wires, cables and vents enter the house with caulk or expanding foam.
- Fit door sweeps and weather stripping on exterior doors, including the garage.
- Fill cracks 1/8 inch or wider in masonry and foundations.
- Screen attic and soffit vents with fine mesh.
Step 2: Treat Clusters Outside
- Soapy water: a solution of about 1 tablespoon of dish soap per quart of water kills boxelder bugs on contact. Spray clusters directly; it has no lasting effect.
- Insecticidal soap: a ready-made option that works the same way.
- Residual insecticide: a product labeled for boxelder bugs or perimeter pests, sprayed on sunny walls, around windows and the foundation in late summer and early fall when bugs first cluster. Follow the label and keep it off plants in bloom.
- Vacuum or hose clusters off walls to break up large groups.
Step 3: Remove Bugs Already Inside
- Vacuum them with a shop vac or a vacuum with a disposable bag, then empty it outdoors. A knee-high stocking stretched inside the hose collects them without messing up the vacuum.
- Sweep them up and drop them into soapy water.
- Don’t crush them on fabric; they stain and smell.
- Put sticky traps near windows where they gather on sunny days.
- Indoor sprays aren’t recommended: bugs hidden in walls die anyway, and dead bugs in wall voids can attract carpet beetles.
Step 4: Change the Yard
- Female boxelder trees (the ones with seeds) close to the house are the main food source. Replacing them with other species reduces numbers over time.
- Rake up and remove fallen boxelder seeds.
- Clear leaf litter, rocks and debris from the foundation where bugs shelter.
What Doesn’t Work Well
| Method | Why not |
|---|---|
| Bacillus thuringiensis (Bt) | Kills caterpillars, not true bugs |
| Diatomaceous earth outdoors | Slow and useless once wet |
| Bug bombs indoors | Don’t reach bugs in walls; leave residue |
| Essential oil repellents | Short-lived, little evidence at clusters of thousands |
Boxelder bug control supplies
- Exterior caulk for window frames and siding
- Door sweeps and weather stripping for exterior doors
- Insecticidal soap for clusters on walls
- Shop vac for removing bugs indoors
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FAQs
Seal cracks, gaps, screens and utility openings on the sunny sides of your home before late August. That is the only lasting fix; sprays and vacuuming deal with bugs already present.
Soapy water, about 1 tablespoon of dish soap per quart of water, kills boxelder bugs on contact when sprayed directly on them.
Boxelder bugs gather on warm, sunny walls in fall to find winter shelter, especially near female boxelder trees and on south- and west-facing walls.
No. Boxelder bugs rarely bite, don’t damage homes and don’t breed indoors, but their droppings can stain and they smell when crushed.
Spray outdoors in late summer and early fall, when boxelder bugs first gather on the outside of the house.
Sources
Facts in this guide are checked against the sources above and reviewed when they change. See how we research in our editorial policy.