Is indoor pesticide spraying safe for fall insects?

Most of the remedies graded on this hub simply don't work — a wasted purchase, nothing more. Interior pesticide spraying against overwintering fall invaders is different, and it's worth being explicit about why it earns a harsher verdict than 'myth.' The EPA states plainly that aerosols and foggers used against brown marmorated stink bugs "will kill these pests in living areas, but they will not prevent more of the insects from emerging from cracks after they dry." The National Pesticide Information Center adds that indoor pesticide use for stink bugs is often ineffective for the same underlying reason: the insects causing the visible nuisance are, for most of the fall and winter, dormant inside a wall void, sealed away from anything sprayed in the living space.

Here is the part that turns 'ineffective' into 'counterproductive,' and it deserves to be said without softening: when insects are killed inside a wall void — whether from a spray that reaches a shallow gap or an insecticidal dust applied directly into the space — their bodies don't disappear. They accumulate inside a cavity you can't see or clean. Penn State Extension's guidance on boxelder bugs is direct that void treatments "may kill thousands of bugs, [but] there is the possibility that carpet beetles will feed on the dead boxelder bugs and subsequently attack woolens, stored dry goods or other natural products in the home." The University of Arkansas makes the same point about Asian lady beetles, warning that dead beetles accumulating in wall voids "can lead to infestation by dermestid beetles which feed of the dead/decomposing" insects. Carpet beetles and dermestids are genuine fabric and stored-goods pests in their own right — you would be trading a nuisance insect you could have vacuumed off a window for an infestation of a different pest, inside a wall you can't easily open. On top of that, a mass of decomposing carcasses causes an odor problem that can linger for weeks or months, often worse and harder to trace than the original insects.

The safe, effective path has two parts, and neither one is an interior spray. First, exclusion done before fall — sealing siding cracks, gaps around window and door frames, and screening vents, finished by mid-September in southern New Hampshire, so fewer insects enter the void in the first place. Second, for anything that does get inside, a vacuum: it removes the insect physically, without leaving a residue and without creating a carcass problem anywhere you can't reach. If a professional treatment is warranted, the legitimate version is a timed exterior perimeter application, applied to the outside of the structure before entry — never an indoor fog or spray. Whatever product is involved in any legitimate application, always read and follow the label, and never use a product labeled for outdoor use inside the home.