More than 75 years ago, the red imported fire ant, Solenopsis invicta Buren, was accidentally brought into Mobile, Alabama, from South America. It now infests more than 325 million acres, comprising most of eleven southern states and Puerto Rico, with infestations also in New Mexico and California. It has recently been reported in northern Mexico, Australia, Taiwan and China. Another species, the black imported fire ant, Solenopsis richteri Forel, was introduced earlier, but this species is limited to northeastern Mississippi, northwestern Alabama, and Tennessee. Colonies move vertically and horizontally in the soil profile to escape floods, droughts, and extreme temperatures. When new colonies are not actively foraging, they may be unaffected by baits or other pesticides applied to the soil surface.
Pesticide treatments are expensive, time-consuming, and limited in their effectiveness. There are three basic approaches:
The best way to treat large areas (hundreds of acres) is by an aerial application of bait. The larger the treatment area, the more slowly reinfestation occurs. However, not all areas can be treated because of label restrictions and application limitations. Even with a bait product, it is not feasible to treat the entire infested area or even a large part of a single state, and untreated areas may be reinfested. If periodic treatments are discontinued, the area may become more infested than it originally was within a year or two.