First, whenever possible exclude boxelder bugs from entering the house by repairing screens and caulking cracks around windows and doors. Bugs that do get in will take up winter residence in wall voids and the attic. They will not cause any structural damage but will become a nuisance throughout the winter. If you are unable to seal exterior cracks you may need to treat wall voids and the attic with insecticidal dust or aerosol.
Second, treat boxelder bugs as they congregate on house siding using one of the three ways outlined below. Bear in mind that bugs become less affected by insecticides later in the fall as their metabolism slows down for winter. Therefore treat as soon as migrating bugs start arriving in early fall.
There are so many treatment type by Insecticide soap, inseticide, dust, aerosol available. But I did below.
1. Spray Demand CS Long Residual Liquid Insecticide around perimeter by 0.2oz per 1 gallon of water rate. You can also cypermethrin or bifenthrin either.
2. Spray Cy-Kick CS Residual Aerosol or Procitra-DL Contact Aerosol into stone wall voids and crack.(I used almost one(1) can), You can also use dust.
3.After 3 Days, If you can not find anymore, just cleaned dead boxelder bugs. If still bugs active, use aerosol into void area more.
4.Another, inexpensive method is to use a large capacity wet/dry type vacuum cleaner to suck up bugs that are accessible. Be sure to empty the canister frequently because dead bugs inside the vacuum will begin to smell fairly quickly.
