Boxelder Bug Control in Kansas City

Boxelder bugs feed mainly on the seeds of boxelder trees, and to a lesser extent on maple seeds. Only the female, seed-bearing boxelder trees produce the seeds they depend on, so a house near one of those trees — or near a row of them along a creek or fence line — sees far more of them than a house a few blocks away.

The second factor is sun. In fall the adults look for warm, sheltered places to spend the winter, and a south- or west-facing wall that soaks up afternoon sun is the warmest surface around. Siding, brick and stone all hold heat, and the bugs gather there by the hundreds. Once they're on the wall, any gap leads them inside.

Adults that survived the winter come out in spring and lay eggs on boxelder trees. The nymphs that hatch are small and bright red, and they feed on the tree through the summer, darkening to black-and-red as they mature.

From September into October, on warm afternoons after the first cool nights, they gather on sunny walls and work their way into gaps around windows, siding, soffits and utility lines. Inside the wall voids and attic they go dormant. On warm winter days, and again in early spring, some of them wake up, follow the warmth the wrong way and end up in living space — which is why people find them crawling on windows in January.

They do not breed or feed indoors. Every boxelder bug you see inside got in the previous fall, and how many there are was set by how many gaps they found then.

The window that matters is late August through October. Sealing before the fall push keeps them out; a treatment on the walls where they gather, timed before they cluster, handles the bugs already arriving. Once they're dormant inside the walls there is no practical way to reach them — you're left vacuuming the ones that wander out until spring.

If you're seeing them inside in the middle of winter, the honest answer is to vacuum them up, note where they're coming from, and plan to seal those spots before next September.

Sealing is what lasts: gaps around window and door trim, siding, soffit vents and utility penetrations. A timed exterior treatment on the walls where they gather handles the bugs already massing there, but on its own it is short-term.

Seal and screen in late summer before they arrive. Caulk around window and door trim, replace worn door sweeps, screen attic and soffit vents, and seal where cable, phone and air-conditioning lines enter the house. Start with the sunny sides.

Vacuum the ones that get inside rather than crushing them — they stain curtains, fabric and light-colored walls. Empty the vacuum outside afterward.

Rake up boxelder seeds and clear leaf litter and debris from along the foundation on the sunny sides of the house, where the bugs gather before they climb.

Spraying them inside the house. The ones you see are the few that wandered out of the wall; the rest are out of reach, and dead bugs left in wall voids can feed carpet beetles and other scavengers.

Bug bombs and foggers. They don't reach the wall voids where the bugs are sleeping, and they leave residue on everything in the room.

Waiting until they're already clustered and moving in. A treatment in late October or November is too late to make much difference that season.

Cutting down your own boxelder tree and expecting them to disappear. It can help, but the bugs fly in from trees on neighboring lots and along creeks, so it isn't a dependable fix on its own.