Entrenched in the South, they are expected to eventually cover the whole country. The least toxic method of dealing with fire ants is to drench the mound with boiling water. Even if this doesn't kill all the ants, it should convince the remaining ones to move. After the water, you should use an insect growth regulator such as Logic, an insect-specific poison that causes sterility in the queen and developing young. A decline in ant population should be noticed after about six to eight weeks.
Logic works best when applied in the early spring after the ants have begun to forage.
It need only be applied once a year, except for the first year, when a large infestation can be treated again in midsummer. If there are ants in the garden, apply only around the garden's edge. Don't apply any directly on the garden. Also, to minimize drift, don't apply on windy days. Logic has low toxicity to other organisms, except for aquatic invertebrates and bees.