Diatomaceous earth is made up of crushed fossilised skeletons of diatoms and algae. It’s cheap and effective to deter critters like ants, cockroaches, bed bugs, ticks, fleas, etc.
The jagged and sharp edges work by scratching the insect’s bodies and dehydrating them. Some say it also goes in their internal system, eyes, joints and more.
Just remember to get the right grade which is food grade or horticultural grade and not the grade use for swimming pools. Not only is it a cheap pest control but it also works wonders as grit for the worms.
Remember to try a little at first in troublesome areas and don’t go overboard as all critters have their part to play in the whole ecosystem.