You can use Diatomaceous Earth for insect control.
If you sprinkle it where the ants come in it will do two things.
Safe as Sand but Lethal to Insects
Diatomaceous Earth, which is also called DE or silicon dioxide, is as chemically inert as road dust, but when properly used, it is very effective against insect pests. Unlike ‘chemical insecticides’ of the last half of the 20th Century, DE is a ‘physical’ or ‘mechanical’ insecticide.
Knowledge of one fact about insects and two facts about DE is required in order to understand how DE can be safe to humans and yet very effective in killing insects.
Insects control their body moisture by means of a complex ‘waxy’ coating on the outside of their exoskeletons, i.e., their shells. This coating is naturally porous, which permit slow loss of water and evaporation. If the waxy coating is damaged, the insect suffers serious injury.
DE is made up of ancient skeletal remains of diatoms. These one-celled creatures have hard, sharp structures that are small enough to cut or pierce the insect’s waxy coating. But the structures are so small that DE feels as soft as baby powder
DE is also an excellent absorbent that is used in cleaning oils spills or kitty litter. This strong absorbency literally sucks the life fluid from insects. Because this is a mechanical process, DE can be literally effective forever.
DE is not toxic to warm blooded or higher animals such as mammals or birds.