This is because ants share food with one another and the larvae, a process called “trophallaxis,” said Kelsey Schail, a graduate student and researcher at UC Riverside. Delayed toxicity is important.

A key to destruction of the colony is to “cut off the head,” explained Tollerup. This means killing the queen, not just the worker ants.

Adult fire ant queens can live up to seven years and can lay up to 1,500 eggs a day, Schail said, and there can be multiple queens within a colony.

With proper baiting and treatment, she said an 80 percent to 90 percent control of ant pests can be expected in almonds.

But she warned that reinvasion is common. Schail said it’s because products used to treat ants are not 100 percent effective, queens are produced continually and lay thousands of eggs daily, and queens can disperse for 12 miles or more.

“Re-infestation from neighboring colonies means you must treat every year,” Schail said.

Granular bait stations reduce environmental contamination, Tollerup said.

Among granular baits includes Clinch (abamectin), a relatively fast-acting stomach poison which takes seven to 10 days; and Altrevin (metaflmizone), also a fast-acting stomach poison that takes three to seven days. Altrevin does not appear to kill the colony.

Extinguish (methoprene) is an insect growth regulator that is not fast-acting, taking three to four weeks and as much as eight weeks for “substantial” effect. Esteem (pyriproxifen) is another insect growth regulator that operates in much the same way – over time.

Schail said fast acting products include hydramethynon, metaflumizone, and chlorpyrifos.

She said it is important to take into account factors that can impact bait efficacy.

Schail recommended applications when soil temperatures are above 60 degrees and there is more forager activity. It’s best to not apply bait for six hours after a rain, avoid irrigating for 24-to-48 hours after applying, and not applying bait near water sources.

The bait should be fresh, she said.