Garden News: Control ants with fresh baits, insecticides

Warmer weather brings many things to our landscapes, including the dreaded fire ants.

Fire ants are most active when soil temperatures begin to warm up, says LSU AgCenter entomologist Alan Morgan. The critters begin to move around the landscape and forage when temperatures are above 70 degrees but below 90 degrees.

You can control fire ants with baits or granular insecticides, Morgan says.

Baits are broadcast over an entire area for foraging ants to collect and carry back to their colonies. One of the advantages of broadcast treatments is that colonies may be controlled before mounds appear.

Baits are insecticides that have been impregnated into ground corn cobs and treated with soybean oil. The oil attracts the ants, and the insecticide kills them.

Morgan warns, however, that baits have a short shelf life. The soybean oil that’s used as an attractant tends to turn rancid, and the ants will no longer feed on the bait.

“It’s important to use fresh bait to be sure your treatment is effective,” he says.

Another type of fire ant control, broadcast granular insecticides, works by forming a relatively long-lasting barrier on the soil surface.

Baits are generally only effective in the area where they’re distributed. This means that if homeowners treat only their own properties, fire ants may move to a neighboring lot.

An alternative to broadcast insecticides is a mound treatment alone. “It might be necessary to treat a colony more than once in order to kill the queen,” Morgan says.

Insecticide mound treatments include dusts, granules, baits and drenches. Most product labels for fire ant mound treatments state specifically where the labeled dosage should be placed.

Granular insecticides for mounds are applied and then watered in. “They’re quick-acting,” Morgan says.

Baits, on the other hand, must be distributed when the weather is dry — no rain and no wet lawns, he says.

The entomologist also warns that some fire ant formulations are not labeled for use in vegetable gardens. “It’s important to read the label and use the products appropriately,” he says.

Got a gardening question? Write to GardenNews@agcenter.lsu.edu.