Gary Heston wrote:

Almost anything with hard, sharp crystals (i.e., Comet or Ajax type
powdered abrasive cleaners) will also work; the function of the boric
acid powder is to scratch the exoskeleton of the insects and cause
them to dry out. Boric acid is pretty safe stuff, and will wash away
(unlike the abrasive cleaners).

diatomaceous earth used in some pool filters will also work, supposedly.