Wow, boxelder bugs have exploded in population over the past month. These pesky critters are common and well-known in Wisconsin during late spring and early summer. And, unfortunately, when the weather starts to cool down, some of us get to know them even better. With several frosts behind us, now is the time when boxelder bugs start looking for a place to overwinter, which could be your home!


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Adults are about ½ inch long and black with orange or red markings right behind the head. Their wings lay flat over their bodies which form an ‘X’. Immature bugs are red and black and are as small as 1/16th of an inch.


Boxelder bugs overwinter in the adult stage. After a frost, boxelder bugs move to seek shelter from the cold, during which time homes are invaded. They can move hundreds of yards from boxelder trees. They tend to congregate in the sunshine on the south sides of buildings and homes, but also on trees and rocks. They can enter your home through cracks in the foundation, siding, gaps along windows and doors, and other small openings. While inside walls and attics, boxelder bugs remain inactive and largely go unnoticed. However, they quickly become a nuisance after the heat of the sun or a furnace spurs them into activity, at which time they begin to make their presence known in homes.

In the spring, the bugs lay their eggs almost entirely on boxelder trees, particularly seeds produced by the female trees. They can also feed on maple and ash trees.


On the bright side, boxelder bugs do not reproduce indoors and are harmless to your home and its furnishings. They also do not bite or sting. Eggs are laid almost entirely on boxelder trees, particularly seeds produced by the female trees. They can also feed on maple and ash trees, causing no damage to the tree. The real reason these bugs are considered a pest is due to their habit of migrating in large numbers inside homes or buildings. Once inside, boxelder bugs can also stain walls and curtains with their excrement.


The best treatment for boxelder bugs is prevention, which keeps them from entering your home in the first place.

Here’s your honey-do list:

  • Repair damaged window or door screens.
  • Repair soffit vent screens.
  • Seal areas where TV wires, phone lines, and other utility wires, pipes, and dryer vents enter your home.
  • Install door sweeps or thresholds to all exterior entry doors. For garage doors, it works best to install a rubber seal along the bottom of the door.
  • Insecticides around the exterior of homes or buildings can create a barrier that prevents the bugs from entering. For treatment purposes, it’s best to prevent boxelder bugs with insecticides, as opposed to waiting until they have already migrated inside. Plus, this reduces your exposure to pesticides inside your home or building. Make sure you always follow label directions carefully before using any pesticide.
  • An experienced pest control technician has the tools, products, and know how for boxelder bugs. He or she can also recommend non-chemical measures that I’ve mentioned above.
  • If boxelder bugs are found inside, the best option is to physically remove them with a vacuum.
  • Removing boxelder trees as a means of preventing boxelder bugs is not practical or recommended because of how far the pests can travel. The benefits of having trees in a landscape outweigh the occasional infestation. However, you can spray trees with an approved insecticide.

If you are experiencing a boxelder infestation in your home or building, it is best to call a professional.

To view the complete article as it appeared in the Menomonee Falls Patch, click here.

About Shane McCoy

Shane McCoy is an Associate Certified Entomologist with 17 years of experience in Pest Management and is the Technical Training Director for Wil-Kil Pest Control servicing Wisconsin and Illinois. You can find out more information about Wil-Kil at or contact your local office at {ap_snippet:global-toll-free-tracking-number}. You can also follow Wil-Kil on Facebook and Twitter (@WilKilPest).

Wil-Kil Pest Control’s Pest of the Month: The Boxelder Bug in Sun Prairie, WI

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