Red imported fire ants (Solenopsis invicta) represent a considerable threat to the biodiversity and sustainability of grasslands in the southern United States. Managers typically utilize chemical control methods on individual mounds as part of their strategy to mitigate for fire ant invasion. We established an experiment in two different ecoregions of Texas to determine (1) the efficacy of individual mound treatment, based on the proportion of mounds that are likely to be found in a unit, and (2) to track changes in the densities of fire ant mounds in response to long-term applications of prescribed fire. Experiments were located at the Rob and Bessie Welder Wildlife Refuge located near Sinton, TX along the Gulf Coast ecoregion and the Harris Ranch located near Breckenridge, TX in the Rolling Plains. Eighteen plots were established at each site and assigned random fire treatments of burned annually, burned once, or unburned. The number of fire ant mounds was compared in burned and unburned plots immediately after conducting fire treatments.

Results/Conclusions

We found 33% and 57% fewer mounds in unburned plots at Welder Wildlife Refuge and Harris Ranch, respectively, due to the removal of herbaceous plants that visually obstructed small, irregular fire ant mounds. Such findings illustrate that chemical applications of individual mound treatment may not control fire ants because a substantial portion of the population is not found by chemical applicators. Using chemical control methods in combination with a biological agent, such as fire, that increases the capacity to locate fire ant mounds may improve fire ant control. Ongoing research will build upon the ability of fire to act as a biological control agent by tracking the movement of fire ant mounds in response to fire treatments. These data will be used to guide sustainable management practices in dryland ecosystems to better manage for fire ant invasion.