Fire ants can be a problem in almonds, stinging workers and damaging nuts.
So, identifying them and treating for them is a challenge, particularly given the number of other ants – non-pests in almonds – that abound.
“Every orchard has a truckload,” said Kris Tollerup, integrated pest management (IPM) advisor with the University of California (UC) Cooperative Extension at the Kearney Agriculture Center.
Tollerup said there are some 270 species of ants in California and few are pests in almonds.
Among the agricultural pests is the Argentine ant, which fancies sweets and plagues citrus growers especially. It’s not a threat to almonds and is more likely in coastal areas, not almond growing regions.
Nor are others that include the Pyramid and the Formica (Native Grey).
“The Harvester ant is also not a problem unless it’s up your pant leg, and that will hurt for a week,” Tollerup said. “But it’s not an almond pest.”
One way to identify the fire ant, which likes lipids found in almonds, is that it has two petiole nodes. Additionally, its tailings - like tailings from a mine - are dispersed and have several small entrance holes. They are active when disturbed, and have a mostly red and blackish abdomen.
The fire ant can go even create openings in the soft-shelled Nonpareil almond variety, causing damage to the kernel.
Tollerup said pyramid ants can be distinguished by their diffuse nest tailings with large entrance holes. Harvester ants have structured nest tailings that are usually in direct sunlight, while the Western fire ant prefers shade and can be associated with weeds. The Native Gray Ant has diffuse nest tailings and large entrance holes.
Snacks figure into the field collection and monitoring of ants.
For fire ants, a favorite is Fritos placed whole in a vial. The morning is the best time to collect specimens.
Bologna – “the cheaper the better,” Tollerup said – is used to attract sugar-feeding ants.
He recommended monitoring for ants in April and May in the southern San Joaquin Valley (SJV) and in June in the northern SJV. He said IPM guidelines for monitoring are available on line, and those show that the percent of damage to almonds increases the longer they are left on the ground in orchards.
One of the challenges to ant control is that using something that kills quickly may not be best.
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.