Should I treat exterior perimeter for fall bugs?

This is the one question in this hub where Anchor's own service really enters the picture, so it's worth being especially careful about overselling it. Penn State Extension's own framing is that an exterior perimeter application 'may offer some relief from infestations where the task of completely sealing the exterior is difficult or impossible' — note the qualifier. This isn't presented as a universally superior option; it's presented as a fallback specifically for homes where mechanical exclusion, the thing that actually has the strongest evidence in this hub, can't be fully done.

So the real answer to 'should I' starts with a different question: have you sealed what you can seal? If the visible cracks, gaps, and vents on your house are caulked and screened, an exterior perimeter treatment adds a supplemental layer of protection on top of that work. If the sealing hasn't been done yet, the caulk gun is the higher-value first step, not the spray.

Colorado State Extension frames late-summer exterior residual treatment as effective specifically 'as a supplement to (not a substitution for)' sealing — a phrase worth repeating because it's the load-bearing distinction on this page. The treatment adds a residual layer on exterior landing surfaces that can intercept insects before they cross into a gap; it doesn't close the gap itself, and it doesn't last as long as many people assume, since pyrethroid-class products break down under sunlight and lose much of their effect within days to a few weeks.

What it truly cannot do: reach insects already inside a wall void, substitute for a caulk gun on gaps you could seal yourself, or work at all once applied in winter, when there's no insect activity on the exterior surface left to intercept.

It's worth being clear that this question is specifically about the exterior perimeter, and the answer changes completely if the question shifts to spraying inside the house. Penn State's guidance on void treatments is a genuine warning, not a hedge: insecticidal dust or spray treatments to wall voids where insects overwinter can kill many insects, but the dead bodies become food for carpet beetles and other dermestid pests, which then go on to attack woolens and stored fabrics — a real backfire, not just wasted effort.

So the answer to 'should I treat' depends entirely on which side of the wall you mean. Exterior, timed before entry, as a supplement to sealing: a reasonable, modest yes. Interior, at any time, for overwintering insects: no, and it can make things worse.

This is precisely the lane a licensed applicator actually occupies: a timed exterior perimeter application, in late summer or early fall, before insects enter, on the home's warm southern and western exposures where they concentrate — applied as a backup where a homeowner's own sealing can't fully close every gap, never as a replacement for it, and never as an indoor treatment. The closing note, repeated because it's the one line that matters most: the treatment only works if it's early. A visit scheduled for December can't do this job, and no legitimate provider should tell you otherwise.