Stink Bugs and Boxelder Bugs in Central Ohio Homes

Why do stink bugs and boxelder bugs gather on your house?

They are overwintering, which means finding a sheltered spot to wait out cold weather. As days shorten in September and October, adults leave gardens, trees and fields and fly to the warmest surface they can find. A south or west wall in afternoon sun, especially with light siding, is the best fit.

An Ohio State Extension educator describes boxelder bugs and brown marmorated stink bugs massing on the warm sides of homes and finding their way in through cracks and crevices. They slip behind trim, into soffits and around window frames, then go dormant between the studs.

That is why bugs appear indoors in January or March. A warm day wakes the ones in the wall, and they head toward the light, which is usually your living room window.

How do you tell the fall invaders apart?

Three insects use this trick in central Ohio. They look alike from a distance, but the details differ.

Our page on stink bug control covers the species and the treatment in more detail. Do not confuse any of these with the spotted lanternfly, which is a plant feeder and not a house invader. See our post on spotted lanternfly in Ohio.

Why do boxelder bugs show up where they do?

Boxelder bugs develop on seed-bearing boxelder, maple and ash trees, so a female boxelder tree near the house can feed the population every year. Removing a large tree is rarely practical, which is why sealing matters more than culling.

Powell is a fair example of the pattern. The median home was built in 2001 and only about 11% are rented (ACS 2019-23), so many are owner-maintained houses with sunny exposures facing the lots and tree lines of Delaware County. Wide southern walls get hit first, then the bugs find their way into the soffits and trim.

How do you keep stink bugs out of the walls?

Exclusion is the answer, meaning you close the gaps insects use. Do it before the bugs arrive, since caulking in November traps whatever is already inside. Extension guidance puts exterior caulking at temperatures above about 40 degrees.

1. Walk the outside in late summerCheck around windows, doors, utility lines, siding seams and fascia boards.
2. Seal gaps with exterior-grade caulkA University of Kentucky Extension publication notes that some insects fit through a gap about one-eighth of an inch wide.
3. Repair screens and door sweepsTorn screens and worn sweeps are open doors.
4. Add mesh behind ventsSoffit and ridge vents need to breathe, so use fine mesh and not caulk.
5. Consider an outside treatment before the waveA perimeter treatment goes along the foundation and sunny walls, per label directions, and works only before the bugs go into the wall.

A perimeter treatment is a band of product on the lower wall and foundation. It reduces the numbers crossing the line, and it works alongside sealing, not in place of it.

What is the fall bug calendar for a Columbus house?

Timing decides how much work the season takes. This is the order we suggest for a central Ohio house.

1. August: walk the outside, fix torn screens and door sweeps, and mark every gap you find with painter's tape.
2. Late August to early September: caulk the gaps on dry days when it is above about 40 degrees, and call about an outside treatment before the first wave.
3. September to November: expect bugs on the sunny walls. Leave them alone outside, and keep windows closed on warm afternoons.
4. December to March: pick up the stragglers that wake on warm days, and avoid spraying into the wall voids.
5. April and May: the bugs head back out, since OSU notes they overwinter as adults and emerge when spring warms. Check your caulk and note the gaps they use.

What if the bugs are already in the wall?

Sealing after they are in only locks the bugs inside, and some will find their way into the living space instead. Seal the gaps you can see from the inside, such as around baseboards and light fixtures, and wait until spring for the exterior work. Plan the next summer's caulking and treatment before the bugs return.

What should you do once they are inside?

Vacuum them. A hose attachment picks them up without crushing them, and crushing is what releases the stink bug odor. Empty the canister or bag outside, since the smell lingers.

Avoid spraying aerosols into wall voids or around lights. It kills a few and leaves the rest. Dead bugs in a wall can also feed carpet beetle larvae later, so cutting the numbers before they enter is the goal.

Expect a few stragglers from January to April. If you are seeing dozens a day, there are many more in the walls, and a second round of sealing next summer will help more than anything done now.

How do you remove stink bugs without the smell?

OSU Extension suggests picking them up with tape, a tissue or a plastic glove, because they can stain skin and fabric. Drop them in a bag or jar and freeze it for about a day, or vacuum them and empty the vacuum outdoors right away. The authors do not recommend insecticides indoors, since the bugs cause no damage and more keep coming in.

A light-colored curtain beside a south window is where most of them end up. A small jar with a lid kept near that window makes the job a ten-second task.