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By Ramona Frances

Agriculture scientists who measure the distance ants fly and record weather conditions that trigger aerial swarming have come closer to understanding how ants spread in California.

Red Imported Fire Ants (RIFA) found in the Chowchilla area in late 1990s are an ongoing challenge for California Department of Food and Agriculture, which works relentlessly to slow down or prevent the spread. RIFA, sometimes found in beehives, are believed to have hitchhiked on wooden hives placed in orchards during almond bloom, and from there built mounds in the orchards. Since RIFA were discovered, ongoing efforts have been underway to keep the invasive ants contained, if not eradicated.

A report in mid-July from CDFA said 118 properties in Madera County are now being treated for RIFA. Crews surveyed 40 properties last month and found nothing suspicious.

Red Imported Fire Ants are small and copper colored (in Madera County) and are often confused with native fire ants, which are red. The coloring of the Red Imported Fire Ant may vary depending on which area of the country they are found in. Red Imported Fire Ants are black in some southern states.

The food source RIFA prefers contains oil and protein. Almond kernels attract them because they contain both, said Art Gilbert, senior entomologist with CDFA who oversee's the Chowchilla eradication project.

Research conducted by Riverside entomologists Michael Rust and Les Greenberg include tethering ants to flight mills to measure their flight duration and speed.

"This (research) helps us to know more ant behaviors, which may influence the way we do our surveys," Gilbert said.

"If imported ants fly a half a mile and we only survey a quarter of a mile, it would change how we're doing things."

The survey to monitor the potential spread of RIFA will continue to help gauge how effective the bait and hormone treatment is.

New data shows RIFA flights are spurred by warm weather, rainfall and subsequent high humidity. In addition, reproductive fire ants have wings, and fly and mate in the air.

"One way is to study them in lab," Greenberg said, "taking female ants and attaching a very fine wire to their thorax and putting them on flight mill."

Greenberg said a flight mill is basically a piano wire that spins around a balanced pivot.

"We attach an ant to one end of the wire and get the ant to fly. Under the right conditions it will fly in circles on the machine. We can record how long it takes it to make a complete circle and also record its speed and total fight time. From that information we can determine how far the flight would have been," he said.

In nature, fire ants fly in a nearly straight line, but Greenberg and Rust translate the data to determine how long the flight time would be in nature.

In addition, Greenberg said fire ant flights are triggered by rainfall. In Texas, where Greenberg studied fire ants for 15 years it would often rain in the morning, and after it dried up in the afternoon, the ants would take off and fly.

"I have seen flights triggered in Southern California as a result of 'on and off' irrigation and sprinklers," he said.

Drip lines would be more effective in preventing flights as long as water doesn't touch the mound. It's also possible high humidity conditions around the mound could cause flight. "Here in southern California, the air is very dry. Fire ants like warm weather rainfall and respond to sprinklers," he said.

Greenberg said the longest female ant flight was an hour and 40 minutes in the labratory, which translates to a four mile flight.

"But the device had some drag on it, which cuts normal flight speed in half," Greenberg said.

RIFA are not native to United States. The U.S. Department of Agriculture believes the ants came from South America aboard cargo ships that docked in Mobile, Ala. in the 1930s. Today, fire ants infest more than 300 million acres in 12 states across the southern U.S., Puerto Rico and China.

If property owners suspect they have RIFA, they are asked to call the toll free hotline at 1-888-4FIREANT.

Ramona Frances Ramona Frances is a staff columnist, writer and photographer for the Madera Tribune. You may contact Ramona at 674.8134 ext. 222 or by e-mail ramona (at) maderatribune.net The Madera Tribune online subscription To subscribe or log on, CLICK HERE. For more information first, CLICK HERE.