The autumn invasion of boxelder bugs constitutes more of a nuisance than a threat. While the bugs don’t bite or harm people, when large numbers are present in interior spaces their excrement can stain fabrics and surfaces. Learn how to show this seasonal pest the door.
A Bug’s Life
Normally, boxelder bugs spend winter in cracks and crevices on box elder tree trunks. Unfortunately, the insects don’t distinguish between a house and a tree. To them, both offer shelter.
Once the bugs squeeze their way inside a home, they typically overwinter in attics or wall voids. On mild, sunny days, insects become active and follow warmth into interior living spaces. Because the bugs seek toasty, sunny spots, they’ll often gather near windows.
In spring, the bugs exit to the great outdoors, where adults feed, mate and lay eggs. Juvenile forms feast all summer long, fueling growth to adulthood. Their favorite food? Seedpods of female box elder trees. They also feed on ash and maple seeds.
Two Key Points
1. Boxelder bug populations balloon when hot, dry summers are followed by warm springs. If last spring was on the warm side and summer is sizzling and crispy, boxelder bugs will be numerous come fall.
2. Scientists have identified three characteristics of buildings that boxelder bugs find attractive:
- Large southern or western exposure walls that are sunny and warm
- Taller than surrounding structures
- Isolated on an open expanse of flat ground
Bug-Proofing Your Home
To beat the fall insect invasion and prevent boxelder bugs from spending the winter months in your home, follow these simple tips:
- Inspect, repair and/or replace all screens – in windows, doors, roof and soffit vents and exhaust fans (kitchen and bath).
- Seal spots where items penetrate your home’s exterior (utility wires and pipes, dryer vents, etc.). Seal openings along siding seams, doors, skylights and windows. Use caulk, polyurethane expandable spray foam, copper mesh or other sealants. Insects only need a 1/8-inch opening to gain entry.
- Install/replace door sweeps and/or thresholds for exterior doors. Inspect/replace the rubber seal along the bottom of garage doors.
- Inspect junctures of different materials, such as wood and concrete block or wood siding and brick. Seal cracks with caulk, such as silicone, silicone/acrylic or elastometric latex.
- Vinyl siding offers ample openings for insects due to the nature of the construction. A properly installed house wrap beneath siding should prevent bugs from gaining access to interior spaces.
- Do not seal weep holes located at the bottom of stone or brick veneer walls. Purchase ventilation plugs to insert into weep holes.
- Apply an insecticide perimeter treatment around the exterior of your home to create a barrier against would-be insect invaders
How To Get Rid of Boxelder Bugs
- Blast clusters of bugs from your house with the garden hose. When bugs start to gather, they do attract more. Alternatively, use a wet/dry vac.
- Sweep or vacuum bugs and physically remove the bodies from your home. If you use a vacuum, empty the bag or receptacle immediately after gathering large numbers of bugs. Otherwise, the carcasses will stink.
- Spray a mixture of soap and water (laundry detergents work well) to kill bugs on contact. The soap must directly contact insects to be effective. Or try an insect killer specifically formulated for use indoors.