How Long Does Terro Ant Bait Take to Kill Ants?

Terro Liquid Ant Bait is a sweet liquid containing sodium tetraborate decahydrate, better known as borax. The bait kills individual ants within 48 hours after they consume it. During that time, an exposed ant carries the bait back to the nest and spreads it to other ants, killing them as well. Large nests may take several weeks to completely eradicate.

Ants return Terro ant bait to the nest, killing all the other ants within weeks.

Types of Ants It Kills

Terro ant bait is formulated for sweet-eating ants, including Argentine ants, acrobat ants, big-headed ants, cornfield ants, crazy ants, ghost ants, little black ants, odorous house ants, pavement ants, pharaoh ants and white-footed ants. Some species, particularly Argentine ants and pharaoh ants, are difficult to eradicate completely with baits because of their extremely large colony size. Terro Perimeter Ant Bait Plus is formulated for carpenter ant control in addition to the sweet-eating ants mentioned above.

Why It Works

Terro ant bait relies on colony behavior for its effectiveness. Ant colonies consist of one or more queen ants, who lay hundreds or even thousands of eggs, but never leave the nest. Worker ants take care of the developing eggs, while other workers forage for food and bring it back to the queens and nursery workers. Ant bait smells like food, but contains poison. Workers find it and bring it back to the nest before the poison kills them.

How It Kills the Nest

The borax in Terro ant bait is an acid that damages ants' digestive systems and weakens their exoskeletons when it sticks to the tiny hairs on their legs. Worker ants, mistaking it for food, feed it to other workers in the nest and, more importantly, to the queen. Once the queen in a colony is poisoned and dies, she can no longer lay eggs to replace the workers, which are also dying of the poison. The colony eventually collapses.

When to Stop Offering the Bait

A small ant colony may succumb to Terro ant bait in a couple of days, while a colony numbering in the hundreds of thousands may take weeks to collapse. As long as ants are coming to the bait station, the colony is still at least partly functional and you should keep the bait station stocked with fresh ant bait. When no ants visit for several days in a row, you can remove the bait station. Be ready to replace it immediately whenever ants return.