Attack of the Argentine ants: your home is their range

October 28th, 2008, 4:30 pm · 4 Comments · posted by Pat Brennan, green living, environment editor

You’re home at last after a hard day’s work, headed for the fridge and something cold to drink, and there they are: long, seething trains of tiny brown ants, a superhighway across your walls, cabinets, counters or floors.

They are overwhelmingly likely to be Argentine ants, a non-native, tropical ant that has become Southern California’s most bothersome ant pest.

And science is coming to the rescue. Studies by area university scientists seek to find the ants’ weaknesses and exploit them, if possible by using a minimum of pesticides.

These ants possess extraordinary abilities that go a long way toward making them so annoying. Unlike in the TV series “Heroes,” however, their super powers don’t come from enhanced genetics. Instead, they arise from a poverty of genes.

The ants invaded the United States by entering through New Orleans in the 1890s, probably aboard ship. But they passed through a “population bottleneck” to do it. The invaders that spread through the nation came from a small number of founders, all genetically similar.

Today, that means the ants can form “supercolonies” miles long. The workers — all females — recognize each other as sisters instead of enemies from competing colonies. They join forces instead of fighting. And then they head for your trash bin.

That makes them tough adversaries. You can douse the ants with bug spray, but you’ve only chopped off one small tendril of the supercolony. Days later, other members can find a new crack in the floor and pour into your home again. And again.

The ants tend to come indoors during heavy rains or episodes of high heat, but can sometimes become more active this time of year in a last mad rush to store up nutrients for the winter.

A $300,000 research project at UC Riverside seeks new ways to fight Argentine ants while keeping pesticides to a minimum. So far, says UCR entomologist Michael Rust, the project, funded by the state Department of Pesticide Regulation and the California Structural Pest Control Board, has focused on helping pest control professionals battle the ants.

Rust hopes to reduce the amount of pesticide that finds its way into water runoff in Southern California.

A key finding: concentrate firepower where the ants are thickest.

“Ants typically walk on edges; they walk on corners,” Rust said. “They usually don’t walk across open surfaces.”

By treating the edges of sidewalks and driveways, he said, pest controllers can greatly reduce the amount of pesticide used as well as making more effective attacks.

But what about advice for homeowners? Rust says his group will likely research homeowner strategies in the future.

In the meantime, Joe and Jane Sixpacks plagued by Argentine ants can find help from UC Integrated Pest Management. The advice includes sponging up the marching columns with soapy water (their mandibles are too tiny to deliver a noticeable bite), and plugging up the holes they come in through.

The site says to try bait traps as well, although Rust said his group’s tests showed little success with commercial traps. The reason: Argentine ants are mainly interested in sweet liquids, not the solids found in bait traps.

John Kabashima, environmental horticultural adviser and exotic-pest specialist for the University of California Cooperative Extension, says he’s had some luck placing small dishes of sugar water in his yard. The ants are drawn away from his home, get their nourishment and return, without causing mischief, to their supercolony.

Related links:

Reader comments: We want this to be a place where people discuss and debate ideas that foster stronger communities. We expect people to differ -- judgment and opinion are subjective -- and we encourage free speech and the exchange of ideas. But you are participating in a community that is intended for all of our users and we prohibit profanity, vulgarity, racial, sexual and homophobic remarks, threats, harassment and personal attacks. Here's the full User Agreement. Thank you for making this a safe place worth preserving and sharing. Share this: The icons below make it easy to share this post with others. First icon e-mails a link.