The only way I have found to eliminate them is using an Ortho Sprayer filled with several cups of Dish Soap or  Laundry detergent. Yup, you read right, liquid dish soap or laundry detergent. Set the sprayer on the 2oz setting, just so the mixture creates a foam. For some reason, this concoction will kill them in their tracks. I’d love to know how this really works and I found this by accident while cleaning some garbage cans. At 1 to 2 oz per gallon concentration, the spray does not hurt plants & trees. I told a few people about this and now the whole neighborhood is in on the Box Elder Bug War. As we’ve learned, any cheap liquid dish soap works as will any non-phosphorus laundry detergent. If there are any Entomologists out there that can answer this mystery, feel free to comment.

Note: One reply below has shed light as to why a simple soap & water solution will kill them; Apparently these insects breath through tiny holes in the side of their abdomen. The soap solution effectively plugs the holes and they quickly suffocate. Thanks Ken!

Here is the gruesome aftermath of a good detergent wash down. You don’t need the volume of suds shown in the photo, 1 oz per gallon of liquid soap should kill 98% of Box Elder Beetles.

Increase the dosage if needed.
Very effective and leaves a fresh clean scent!

Follow up: If they’ve already made it inside your home, use a small wet / dry shop vac to collect them intruders and place a few cups of soap & water in the collection canister to kill them.  Find the entrance and plug it with liquid spray foam, such as “Great Stuff” or a similar brand.
Be pro-active: In spring and early summer, watch for tiny swarms right after they hatch and soap ‘em down good so they can’t spread, mature and reproduce.