First, is it worth treating your pasture at all? If the answer is yes, there are several baits that can be broadcast for fire ant control in pastures. These baits cost about $10-15 per acre. The cost of labor and equipment needed to apply the bait must also be considered.
Baits containing hydramethylnon (Amdro Pro), pyriproxyfen (Esteem), (s)-methoprene (Extinguish), or a mixture of hydramethylnon and (s)-methoprene (Extinguish Plus) are currently labeled for use in cattle pastures. In addition to the above materials, Award Fire Ant Bait (containing fenoxycarb) can be applied to pastures grazed by horses.
To treat more than 100 acres, consider aerial application of fire ant bait.
Fire ant baits can be used as individual mound treatments but may take longer to work than other available treatments. It would not be economical to treat many mounds individually because of the cost of the materials and labor involved. A mound drench containing carbaryl (such as Sevin 4F, Sevin XLR, and Sevin 80S, that are labeled for use in pastures) can also be applied to individual mounds.
Note: Not every fire ant control product is registered (legal to use) in every state. Product availability may be limited, especially in western states with very few fire ants. Purchase your fire ant control material in the state where you live, and make sure you find "fire ants" on the label of the pesticide. Your county Extension office can help you confirm if a particular pesticide is registered in your state.
Find more information about fire ants in eXtension's Imported Fire Ant Resource Area.