We got roaches from an Amazon package, I suspect. My wife and I are both compulsively clean people, but we live in an older place so there is ostensibly decades worth of random organic material around to sustain roach colonies. It started one spring with seeing some instars around the kitchen every few days and then it became full roaches about a week later. I did not take it seriously at first and just treated with hardware store sprays and powders. This was insufficient.

What eventually worked was baits and a little chemical called Alpine WSG. I bought a sprayer and basically coated the entire house in it twice, six weeks apart. We have not seen a single roach since then. I respray once per year just in case.

Also, boric acid doesn’t work with German roaches. It is a waste of time. If you solved roach problem with that or diatomaceous earth, then you had a entry problem, not an infestation.

We also had racoons breeding in our attic at one point, which is a very awkward situation because I felt bad trapping them so I just waited for them to leave and then sealed where they were getting in.