Recent media reports about the discovery of Imported fire ants in Kern and Fresno counties should not cause farmers and rural homeowners a high level of anxiety.

"These were very isolated finds," said Mark Freeman, University of California Cooperative Extension nut crops farm advisor for Fresno County. "So far, the California Department of Food and Agriculture hasn't found movement outside the target areas."

Freeman has been fielding calls from worried Fresno County residents who encounter red and black ants on their farms or property. Most of these ants, he said, are California fire ants (also called Southern fire ants), which were long ago established in the state.

"We've lived with these ants and several other species of ants for decades," Freeman said. "They do pose problems to farmers and homeowners. We are currently conducting research to find better ways to control these pests."

Imported fire ants were found last October in the Lost Hills area of Kern County and a month ago in a Kerman almond orchard. They were transported to California from Texas in beehives brought to the farms to pollinate crops. All farms where trucks that are known to have delivered infested beehives are being surveyed regularly. The two locations where Imported fire ant colonies were found will be treated and monitored for at least two years, Freeman said.

"Quarantine areas have been established, so scientists are focused on eradicating the pest. There's no question of trying to live with it," Freeman said. "We're treating this infestation very seriously."

However, the likelihood of finding Imported fire ants in urban areas remains exceedingly low. "All finds have been associated with agriculture," he said.

There is a slim possibility that fire ants have established colonies in other San Joaquin Valley areas. Imported and California fire ants are very difficult to distinguish in the field. To a trained eye, the California ant has a shiny red head and black abdomen; while the Imported ant is a duller, more hazy red and black color.

The most telling difference between the Imported and native varieties is the unusually large mound built by the Imported fire ant. Imported fire ant mounds are 18 to 24 inches wide and 5 to 6 inches high, Freeman said. If the top crust of an Imported fire ant mound is removed, underneath the ants have excavated large tunnels that maintain their structure.

"The soil looks like Swiss cheese," Freeman said. "In mounds built by California fire ants, the tunnels just fall apart. It's all soft."

Samples of suspicious ant finds should be collected carefully and sent to the local agricultural commissioner's office.

Editors: For more information contact Mark Freeman at (209) 456-7265 or mwfreeman@ucdavis.edu.

Jeannette Warnert
Public Information Representative
Ag and Natural Resources
UC Center
550 E. Shaw Avenue
Fresno, CA 93710