What time of year should I pest-proof?

The timing isn't arbitrary — it's set by when insects actually start moving toward buildings. UNH Cooperative Extension's data puts brown marmorated stink bug massing on New Hampshire homes at roughly September 1 through 20, and boxelder bugs following a similar early-September pattern. Lady beetles fly to walls a bit later, typically late September through October, on afternoons warm enough to trigger the behavior. UNH's blanket guidance across these species is to caulk and seal before early September — which, worked backward from the earliest massing dates, leaves realistically a few weeks in August as the true safety margin.

That's why 'pest-proof in fall' is too vague to be useful. By the time most people think of fall as underway, in late September or October, several species have already started arriving. August is uncomfortable to think about as pest season, which is exactly why it's the window that actually works.

This is the correction that separates a real answer from a generic one. NC State Extension and Virginia Tech's joint guidance on brown marmorated stink bugs is direct: 'Do not bug-proof your house in fall, winter, or early spring, which will likely trap BMSB inside… Let them escape on their own in spring and then seal them out before they try to return in late August.' The logic is straightforward once you see it: by the time it's cold enough to notice bugs and think about sealing, many are already inside the wall void, in diapause. Sealing at that point doesn't exclude them — it removes their route back outside, which means more of them end up finding their way into the living space instead, not fewer.

This is a genuinely counterintuitive piece of guidance, and it's the kind of thing a hub built to sell a product would never say, because it tells you not to act on the instinct that shows up exactly when you're motivated to act.

If it's already fall, winter, or early spring, the candid plan changes. Vacuum any insects you see indoors rather than spraying — spraying the interior for overwintering insects is not just ineffective, it leaves carcasses in the wall void that feed carpet beetles and other dermestid pests, trading a nuisance for a fabric-pest problem. Put a specific date on next year's calendar: late August, not a vague 'sometime in fall.'

There's no way to retroactively fix this year from indoors. The real answer to 'what should I do right now if it's already December' is: not much, and that's fine — the fix was never going to happen this month anyway, for anyone.