Fire Ants by State
Red imported fire ants (Solenopsis invicta) have spread across most of the southern United States since their introduction through the port of Mobile, Alabama in the 1930s-1940s. Their range continues to expand as the climate warms. Here's an overview of fire ant distribution across the affected states.
Heavily Infested States
These states have widespread fire ant populations across most or all of their territory:
- Texas — Infested across the eastern two-thirds of the state, from the Gulf Coast north to the Dallas-Fort Worth area and westward to San Antonio and beyond. Texas has both monogyne and polygyne populations and is home to the most extensive fire ant research program in the country at Texas A&M University.
- Florida — Infested statewide. The warm, humid climate and sandy soils are ideal for fire ants. Florida also has significant electrical equipment damage issues due to year-round ant activity.
- Louisiana — Infested statewide. The Gulf Coast region has some of the highest mound densities in the country.
- Mississippi — Infested statewide.
- Alabama — Infested statewide. The original port of entry for RIFA in North America.
- Georgia — Infested statewide, though populations are lighter in the mountainous northern counties.
- South Carolina — Infested across most of the state, with lighter populations in the upstate/mountain region.
Partially Infested States
- North Carolina — Infested across the coastal plain and piedmont regions. The western mountains are generally too cold for established populations.
- Tennessee — Infested in the western and central portions. Fire ants continue to expand northward and eastward.
- Arkansas — Infested in the southern and central portions.
- Oklahoma — Infested in the southern and eastern portions, expanding.
- Virginia — Limited infestations in the southeastern corner (Hampton Roads area).
- New Mexico — Limited infestations in the southeastern corner.
- California — Infested in parts of Southern California (Orange County, Riverside County, San Bernardino County, and others). California maintains an active quarantine and eradication program.
USDA Quarantine Areas
The USDA maintains a federal quarantine on the movement of soil, nursery stock, and other regulated articles from fire ant-infested areas to non-infested areas. This quarantine is designed to slow the spread of fire ants through commercial movement of plants and soil. If you're moving plants, sod, or soil across state lines from an infested area, check the USDA APHIS quarantine maps for current regulated areas.
Range Expansion and Climate Change
Fire ant distribution is limited primarily by cold winter temperatures. Colonies can't survive sustained soil temperatures below about 10°F (-12°C). As average winter temperatures rise, the potential range of fire ants expands northward. Research suggests that fire ants could eventually colonize areas as far north as Virginia, Kentucky, southern Missouri, and southern Kansas if warming trends continue.
Urban heat islands also play a role — fire ants can survive in cities further north than their rural range because urban environments are warmer. Isolated infestations have been found in areas well outside the established range, often associated with movement of infested nursery stock or soil.
What This Means for Treatment
Treatment timing varies by location. In the Deep South (Florida, Gulf Coast, South Texas), fire ants are active nearly year-round and may require 3-4 treatments per year. In the upper South (North Carolina, Tennessee, northern portions of affected states), the active season is shorter and the standard twice-yearly two-step method application (spring and fall) is usually sufficient. See the seasonal treatment timing guide for specific recommendations.