Boric acid has been an effective insecticide for many years. It works on insects after they eat it. Boric acid prevents the insect from turning food into energy. This process cannot happen in humans or animals, so boric acid is relatively low in toxicity to people and pets.
The form of boric acid that many people have used is powder or dust. The dust is applied into the insect's trails and nesting sites. Without suspecting anything, insects walk through the dust. Later, when the insects groom themselves, they swallow some of the boric acid.
Boric acid dust has been very effective in controlling insects that hide in walls and behind baseboards. However, boric acid dust has not been effective for controlling ground-nesting insects like fire ants.
To make boric acid effective for controlling fire ants and other ground-nesting insects, manufacturers have mixed it into bait. There are ant baits in the form of liquid and gel. There are also ant bait pellets that are called granular bait. Boric acid is the active ingredient in several brands of ant bait.
The fire ant bait granules are spread on the lawn and around the ant mounds. The product label has directions for the amount of bait to apply. When the foraging ant workers find the bait granules, they take them back to the nest.
The foragers share the bait granules with the larvae and then with the other ants in the colony. As each ant eats some of the bait, it also receives a dose of the boric acid. The ants share the bait from mouth-to-mouth until all of the ants have eaten some.
Some of the granular boric acid baits are resistant to moisture, so they will not spoil if they get wet. The product label will explain his feature in more detail.
The product label will also have directions for how much bait should be applied. For broadcast applications, the application rate is usually given as an amount of bait for every thousand square feet. Large yards can be treated more easily if they are split into sections. Multiply the length by the width to find the number of square feet.
The label will also explain when and how often the bait can be re-applied. This is important because new fire ant colonies will try to invade when the original fire ants are eliminated.