Aggressive Fire Ants Infest O.C.

An aggressive species of fire ant, previously contained to nurseries and orchards in California, has colonized a 20-mile swath of backyards, parks and other residential areas of suburban Orange County and appears to be spreading, state agricultural officials said Thursday.

The red imported ant, which can attack en masse and inflict painful bites, has plagued southern states in the Gulf of Mexico region for decades. California has kept it under control through regulation and treatment at nurseries and orchards.

Officials said they have also found fire ants at nurseries and orchards in the Central Valley and Santa Barbara County. Three Central Valley orchards are under quarantine.

If not checked, the fire ant “could eventually spread to all areas of the state, except for the driest deserts and coldest mountains,” said David Asakawa, who is heading a 25-member detection team for the California Department of Food and Agriculture.

None of the ants has been found in Los Angeles County. However, county inspectors are monitoring six nurseries that bought supplies from one of the infected Orange County nurseries. The nurseries under watch are concentrated in two areas, around Pico Rivera and Torrance.

Orange County’s manicured lawns, golf courses and green belts are ideal breeding grounds for the ants, which thrive in warm, irrigated turf, scientists said.

More than 70 mounds have been flagged in Orange County over the past two weeks. As many as 40 are in a small park in front of an apartment complex in the Robinson Ranch planned community in south Orange County.

The infestation was discovered last week after the Nevada Department of Agriculture informed California officials that they had intercepted nursery plants being shipped from TY Nurseries in the south county.

That nursery and one next to it probably had no idea they had a fire ant problem, Asakawa said.

The nurseries now are under quarantine. That means every recent plant shipment is being tracked and examined, and thousands of plants due to be sold are being drenched with pesticides and inspected before they can be shipped.

A panel of national and international experts is being assembled, state and county officials said, and will convene within 10 days.

The ants, distinguished by their bright red head and middle portion, will “erupt in a volcanic stream” if their burrows are disturbed, said Nick Nesson, entomologist for the Orange County Agricultural Commission.

In the South, they have destroyed farm machinery, livestock and vegetation--and cost states hundreds of millions of dollars in eradication efforts. In infested areas, lying in the backyard or having a picnic has become a thing of the past, experts said.

The entire stream can crawl rapidly over skin or any other surface, inflicting painful bites along the way. Usually the bites cause a dull, burning sensation that lasts a few hours, followed within 24 hours by a white, raised bump that can become infected if scratched.

In rare instances, a single bite can cause painful welts and even death, said Michael Merchant, an urban fire ant specialist with Texas A&M;’s agricultural extension program. According to studies, an estimated 1 in 10,000 people will suffer a violent allergic reaction that can lead to death, he said.

Normal ant sprays and traps will not wipe out the fire ant, which often has multiple queens burrowed deep under sidewalks, fire hydrants or electrical boxes where they have protection and access to water. State officials want residents to avoid disturbing the mounds until experts devise an eradication plan.

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Times staff writer Jack Leonard contributed to this story.