We live in a rural area near woods. Big thing for our area is that you have to treat the outside too. You bomb for roaches, they leave for a week, then come right back in when it rains. Boric acid all over the inside where you can, especially behind appliances, and the diatomaceous earth around the house. It doesn’t have to be food grade unless you have chickens or something outside that will get into it, and the non food grade is much cheaper.