Liquid Bait Most Effective Killer of Odorous House Ant Colonies

Spring rains bring on hoards of odorous house ants looking for sweets in Missouri’s homes.

They don’t bite or sting, but by the thousands, they are an irritating nuisance.

The sugar-loving ants that smell like coconut when they’re crushed normally collect food from aphids, plantsucking insects that excrete honeydew that ants eat. Rains keep aphids from their normal habits, so worker ants go foraging into homes looking for alternative food sources.

Spilled fruit punch is a sure magnet. The ants love sugar and prefer liquids.

When you spot their long foraging trails, you’ll be tempted to spray, but don’t, said a University of Missouri Extension researcher.

"You’re just killing the workers. That queen is still alive and is going to produce thousands of eggs to replace those workers," said Richard Houseman, MU urban entomologist. "The key to ant control is killing the queen, and with odorous house ants, there are potentially dozens of queens."

So even if you’re keen enough to find a queen or 10 queens, killing them with a spray won’t solve your ant problem.

Instead, put bait where the worker ants work, Houseman said. The workers will take the bait, believing it’s food, straight to their queens.

"But you have to use a lot of bait," he said. Houseman recommends boric acid-based liquid bait, sold in bottles of gel under the brand name Terro. It has low toxicity to humans and pets.

"Boric acid bait is safer around children than most insecticides," Houseman said. Bait stations can be used, but those typically use protein-based solid bait. The odorous house ants normally prefer liquid sugar bait.

Houseman suggested cutting the bottoms off plastic soda or water bottles, leaving about one inch of height. Fill the bottom of the bottles with bait and place several of these along the ant feeding trails.

Odorous house ants, such as this one photographed next to the point of a 0.5 mm mechanical pencil, are finding their way into Missouri homes. The insects come indoors with the onset of spring rains. Photo courtesy of Richard Houseman, University of Missouri.

Also, milk bottle caps turned upside down and filled with bait will work.

"They’ll line up like cattle at a feed trough," Houseman said.

Houseman’s colleague Wayne Bailey, also an MU Extension entomologist, suggested applying Terro on wax paper, in lines of 12 inches or more. He uses the method every spring at his home in Columbia.

"I use it all the time. You get a long feeding line, and the bait isn’t absorbed by the wax paper," Bailey said. "You want that quick knock down where the majority of the ants feed."

Keep replacing bait daily, sometimes twice a day, until the ants stop taking it, Houseman said.

Odorous house ants can form colonies within homes, but nests are more often found outdoors. Colonies are common under debris piles, bricks, stones and within loose tree bark.

"I call them a cavity nester," Houseman said. "They look for empty spaces and build their nests there."

The odorous house ant gets its name from the unique fruity smell it gives off when crushed. Some describe it as smelling like rotten coconuts. Others, like Houseman, call it a pleasant smell akin to ripe coconuts.

"They don’t bite, so you can roll them between your fingers," Houseman said. "It sounds kind of weird. It’s a funny characteristic, but it works. No other ant has that smell."

The odorous house ant workers are all of similar size, about 2 to 3 millimeters long. That’s in contrast to carpenter ant workers, which vary from small to large within the same colony.

"Odorous house ants are probably the most common ants that infest homes in Missouri," Houseman said.

Source: Richard Houseman (573) 882-7181

Chuck Adamson
Extension & Ag Information
(573) 882-6843