Fire Ants in California

After the initial discovery of red imported fire ants in Orange County and parts of Los Angeles County and Riverside County, California, in October 1998, the California Department of Food and Agriculture (CDFA) delineated the infestation and issued proclamations of eradication in three counties encompassing over 204,000 ha.

Fire ant workers tending a queen. Photo by Charles Barr.

Fire ant workers tending a queen. Photo by Charles Barr.

Thereafter, local county agencies were contracted to survey for ants and conduct large-scale broadcast application of fire ant bait products in a sequence based, in part, on considerations produced by Drees et al. (2000). These programs made applications from February 2000 through February 2004, treating over 29,000 sites in one county alone. The treatments were made to most properties four times per year at 3 to 4 month intervals. Post-treatment monitoring began 3 months after the final treatment and showed less than 5% of the sites remaining infested. However, the eradication effort was terminated in February 2004 because of budget reductions. Since then, residents from Orange County and the Coachella Valley in Riverside county have voted to approve a new program initiated in October 2004.

Nevertheless, eradication has not been achieved because not all infested areas were treated or received the full treatment regime. Other areas in California are at a high risk of infestation or have been found to harbor infestations such as in San Diego County. In 2008 fire ant infestations have spread eastward in San Bernardino Co. through the cities of Chino and Ontario. Agricultural areas such as almond orchards in counties in the Central Valley have also been found to harbor infestations and are under state quarantine. These areas of fire ant distribution do not appear on USDA Fire Ant Quarantine maps.

The following resources will help you understand what to do if you find fire ants on your land.