Cattle Production Systems, Pastures and Rangeland Management Strategies
Nonchemical or cultural control methods can reduce losses while maintaining a stable ant population that will help suppress other pests (lone star ticks, filth breeding flies, etc.) and deter the multiple queen form.
Chemical treatment can suppress fire ants in pastureland for $10 to $15 per acre per year. Chemical treatments do not eradicate fire ants, and the treatments need to be repeated periodically. Some bait-formulated insecticides also affect native ant species that compete with fire ants. However, in areas with 20 or more mounds per acre, using baits as part of the Two-Step Method method may be justified. In the Two-Step Method, a fire ant bait is broadcast once or twice a year. These treatments can kill up to 90 percent of the colonies within several weeks to several months. Hydramethylnon bait (AmdroPro) takes 2 to 3 weeks and the effects last for months or until ants re-infest the treated area. Insect growth regulator (IGR) baits containing pyriproxyfen (Esteem) require 6 to 8 weeks to see notable results. The IGR, s-methoprene (Extinguish registered for pastures), require 8 to 12 weeks. Metabolic inhibitor or other faster-acting , non-IGR baits usually provide several months of control. Insect growth regulators usually provide 6-12 months of control depending on the time it takes new fire ant queens to re-invade the area. To provide faster control than you get with an IGR, yet longer-lasting control than you obtained with a faster-acting bait, you can mix the two types of baits together at half rates or use Extinguish Plus, a commercial mixture of hydramethylnon and s-methoprene. The second step in the Two-Step Method is to treat individual mounds that are a particular nuisance. Products containing carbaryl or Sevin are registered as fire ant mound drenches for pastures. Once the broadcast bait treatment has taken effect few individual mounds should need to be treated. Always read and follow the instructions on the product’s label. A list of products registered for fire ants in Tennessee’s pastures can be found in UT Extension’s PB 1690 Insect and Plant Disease Control Manual.
There is great hope that in the future fire ant populations will be suppressed through the release of natural enemies from their native habitats in South America. One type of parasite being investigated is a phorid fly that develops inside the heads of ants. In theory, adult phorid flies looking for worker fire ant hosts suppress ant foraging and allow native ant species to compete more successfully with fire ants. Several phorid species have been released in Tennessee and are established.