As an insecticide, it’s mostly used to kill cockroaches, ants, silverfish, termites and fleas. As an herbicide, it’s best on molds, fungi and some kinds of weeds. Like boric acid, borax is ...

such as by creating boric acid solutions to kill spiders and other insects like earwigs. It works in two different ways. First, it can kill pests when they accidentally ingest the substance.