Why do boxelder bugs come inside each autumn?
Boxelder bugs enter buildings in autumn to overwinter, looking for a sheltered place that stays out of the weather. Attics, wall voids and the gaps around windows give them shelter, and they gather on windowsills inside the house.
The bugs are closely tied to boxelder trees, so the autumn move is toward whatever building is nearby. A building offers a stable place to wait out the cold, and the attic is the usual spot where they settle.
The sign most people see is a group on a sunny window or wall. The bugs move toward light, which is why windows are where they are found.
How do I seal the building against them?
Caulk exterior cracks and holes, repair loose siding and trim, and check window and door frames and attic vents for gaps. Repairs finished before September are the most useful, because the big invasion months are September and October.
The work is the same as for other fall invaders. MSU's advice is to prevent entry by caulking exterior cracks and holes, so the bugs have fewer ways into the walls and attic.
Timing matters. The bugs begin arriving in September, and the peak comes in October. A repair finished in early September keeps the building closed before the peak.
What should I do about the trees near the building?
Remove nearby female boxelder trees where possible, because the bugs are closely tied to them. Where a tree cannot be removed, the technician can explain the options that suit the property, and the homeowner decides what to do with it.
MSU Extension recommends removing nearby female boxelder trees where possible. The trees are a source of bugs that find their way into buildings each autumn, so cutting them reduces the number that come in.
Where a tree cannot come out, the technician can explain how the bugs use it and how to reduce the number that reach the building. Sealing still matters, because bugs can still come from elsewhere on the property. The tree advice is one part of the plan, not the whole plan.
How do I clear the bugs that are already inside?
Vacuum them up and empty the vacuum outside. Insecticides are not the answer for bugs in attics and wall voids, because MSU expects them to work poorly indoors where hidden harborage cannot all be treated.
Vacuuming is the most direct method for bugs in a room or on a window. Use a hose or brush attachment, pick the bugs up quickly and empty the canister or bag outside, since a bug that escapes from a vacuum can get back into the room. Repeat it as new bugs appear.
Insecticide is not a good answer for bugs hidden in attics or wall voids, because the harborage cannot all be reached. A technician advises whether a product is useful for a particular room and explains what it is for. Sealing the building and vacuuming the bugs usually give the most reliable result.
What moves the price up or down for boxelder bug work?
The size of the building, how many entry points need repair, how high the eaves and attic access are and whether tree advice is needed all change the scope. The technician sets the price on site and explains it before any work starts.
A single house with a few windows and an accessible attic is a smaller job than a two-story building with high eaves and many vents. Height and access matter because the upper parts of a building need equipment to inspect and seal. The number of entry points is the main driver of how long the sealing takes.
Tree advice is a separate piece of the work and changes the scope when it is included. Vacuuming and follow-up visits add to it when bugs are heavy in a particular room. Because every building is different, the price is not set before the inspection. It is explained to the owner and approved before any work starts.