Considering the amount of time, energy, resources and funding it takes to battle little fire ants, called one of the worst invasive species in the world, saying a colony is “eradicated” is a big deal.

“We don’t like to throw around the ‘E’ word willy nilly because you say that and then you find ants there,” said Brooke Mahnken, invasive ant/geographic information system supervisor, on Wednesday afternoon at the Old Maui High campus, MISC’s base.

Through a “mega effort” by the MISC Little Fire Ant Crew, which currently only has three members who are involved in public reporting and collaboration, as well as mapping, sampling, surveying and spraying low-toxicity gel bait as a form of birth control, it seems as though humans are winning the war against these insects on Maui.

“We may potentially be close to the ‘E’ word at several monitoring sites,” said Serena Fukushima, public relations and outreach specialist. “Dream scenario, if we eradicate all known populations on Maui, we’ll still always have to continue that outreach to test anywhere just because of the Big Island infestation, transportation and other ants coming in.”

Greatly enlarged by a microscope Wednesday, a dead little fire ant appears on a MISC computer screen. — The Maui News / MATTHEW THAYER photo

Tiny, but mighty

Little fire ants are native to South and Central America. They were first detected on Maui in October of 2009 in Waihee on less than an acre of property, according to MISC. Early detection and community cooperation led to quick eradication of little fire ants in this area, Fukushima said.

These tiny bugs are hard to spot even as Mahnken pointed to a few crawling up and all around a blossomed white ginger plant. Often mistaken for tropical fire ants, little fire ants are orange and red in color, but are about as long as a penny is thick and can easily fall off plants — all identifying signs of little fire ants.

“They sting, not bite, so what you’re feeling is the venom in their sting,” Fukushima said. “People have varying degrees of reactions to the venom.”

Some people may get rashes or welts that last for weeks, while others might have minor reactions to the stings. When little fire ants invade yards and homes, they can also blind pets and cause residents to move away to avoid stings.

Maui Invasive Species Committee Invasive Ant GIS Supervisor Brooke Mahnken wears a purpose designed and built pack Wednesday that is used during ant surveys. — The Maui News / MATTHEW THAYER photo

They can form supercolonies with multiple queens, blanket landscapes and outcompete most other insects in the area, both native and nonnative, Mahnken explained.

A few ant workers and one reproductive queen are all it takes to start up a new colony elsewhere, which is why it’s important to double-check potted plants, materials or equipment that have been sitting for a while before moving them.

Eradicating the workers is meaningless for winning the battle against little fire ants. This is why “the queens need to be taken out,” Mahnken said while doing a follow-up survey on a Haiku property that had called MISC last month to report an infestation.

In Hawaii, the average population density in an infested area is 20,000 individuals per square meter, according to the Hawaii Ant Lab website. Queen density is estimated to be 36 to 77 per square meter.

At the infested Haiku site on Wednesday, Mahnken was equipped with GPS, a tablet, red flag markers, vials with QR codes for digital tracking and just the right amount of peanut butter placed in each tube.

A spray ball shoots water as it is tested Wednesday. The 50-pound, Maui-built apparatus is used to spray little fire ant bait over infested landscapes including tree canopies. — The Maui News / MATTHEW THAYER photo

He anticipated that there will be up to 1,000 QR-coded vials dispersed by the time MISC is done mapping, sampling and treating the property over the next year at the particular site. They even survey 20 meters beyond the property line just to be sure little fire ants are contained inside the perimeter.

Vials are placed roughly 5 meters (or about 16.4 feet) apart to collect ant samples, which are later sent to Little Fire Ant Crew member Monte Tudor-Long, who is sometimes called “Uncle Ant” for his extensive knowledge of ant species across Hawaii. He holds detailed data sets documenting new and existing species at the MISC base.

“He’s bringing an awareness of ant communities in Maui and also through that research and database that he’s starting, it gives us an idea of what ants are where and what those ant populations are looking like,” Fukushima said.

Winning the ant war

After Hilo-based Hawaii Ant Lab formulated a bait recipe to interfere with insect reproduction, MISC replicated the technique and has since been getting successful results.

Maui Invasive Species Committee Field Crew Leader Monte Tudor-Long uses a microscope to view a little fire ant Wednesday at MISC offices at old Maui High School. — The Maui News / MATTHEW THAYER photo

Mixing together water, vegetable oil, xanthan gum (a natural thickening agent), beef liver protein powder or peanut butter, and the key ingredient, Tango, which is a concentrate product that contains S-methoprene (an insect growth regulator), the MISC crew has been able to slowly reduce little fire ants’ population sizes since 2016.

Worker ants feed on the gel bait and bring it back to share with the queen and larvae, and the treatment then slows down larvae growth and egg reproduction, Mahnken said.

The bait sticks to trees and leaves, and is tolerant to moisture.

Treated ant colonies will start to see a reduction in population after about three months as worker ants die from “old age” and reproduction slows, he said.

Treatments are repeated every six weeks for at least a year in order for the insect growth regulator to be effective.

The active ingredient S-methoprene is one of the safest insecticides, he said. It is often used for insect control in food crops and even drinking water, as Tango is registered for use on and under food plants.

“It’s a slower process, but it’s low impact,” he said.

The substance is generally safe, as most of the solution is natural and the team uses low quantities of the hormone, so it does not affect other animals, like birds or mammals.

According to the National Pesticide Information Center, methoprene is relatively nontoxic to birds but can be toxic to some fish and freshwater invertebrates. It breaks down quickly in soil, water and on plants.

Some other ant species and mosquitoes may be impacted by the birth control bait that ingest it, but Mahnken said “we’re not worried about those,” considering there are no native ant species in Hawaii anyway and there’s an overpopulation of mosquitoes.

Per regulations, MISC does not spray the ant birth control mixture near or in water, only on land. For example, in the Twin Falls treatment areas, the team has been spraying away from the ponds and rivers. However, some solutions are safe and permitted to use near streams, such as the one used to spray over Nahiku — a special management area use permit was obtained to treat this particular area.

There is an array of herbicide and pesticide treatments for insects, though they are sometimes temporary, costly and toxic.

“If you were to measure the damage the little fire ants do to the economy and quality of life, it’s absolutely cost effective,” he said. “Living without fire ants as long as you can is worth something.”

As Hawaii acknowledges Stop the Ant Awareness Month in October, Mahnken said that eight sites on Maui are currently in the active treatment phase while six are in the monitoring phase. Once detected, each infestation is treated for about one year, then monitored for about five years to ensure elimination.

Around 90 percent of all infestations are identified through community notifications.

“We are on top of all known infestations here and they are rapidly shrinking and/or gone, so we have a chance to live without little fire ants on Maui,” Mahnken said. “Whereas on the Big Island, for example, they just have to mitigate living with them, which means shutting down 42 county parks every six weeks for treatment, all the schools, all the county buildings and the state buildings.”

Following the conclusion of a three-week survey of what was formerly Maui’s largest known little fire ant infestation in Nahiku, where the MISC crew stayed in Hana and bushwhacked through the thick forest to sample and treat the 175-acre site, Fukushima said they came back with “promising results” with less than a third of the area still infested.

“The community has been really supportive in controlling the little fire ants in this area,” she said.

However, Mahnken said that they continue to treat 85 acres because much of it is not able to be surveyed on foot, which is where their novel helicopter operations by MISC and Hawaii Ant Lab come into play — insect growth regulator is sprayed from the air, a technique that conservationists worldwide, including in Guam, have been eyeing.

“This is a magnitude that’s never been attempted anywhere, especially the technique that we’re using,” he said. “There’s international communities that know that we’re doing this and are kind of waiting on our results. They would like to replicate that sort of thing.”

The three-person ant crew was again mixing up large quantities of treatment, over 100 gallons, on Wednesday afternoon for a planned “heli-op” in Nahiku on Thursday morning. Mahnken said they will continue to treat “these unknown areas” until they no longer find any ants.

“We cut the treatment zone exactly in half after the first all-staff survey in 2021, from 175 acres to 87.5 acres,” Tudor-Long said.

Awareness and prevention

In addition to advocating and teaching best practices for nursery management and regulation statewide, as well as conducting public outreach and educating youth through little fire ant programs, MISC has been recommending folks to collect ants in their yards for identification at least once per year and every time new materials are purchased, such as mulch or nursery plants.

“The community side and public relations side is really just getting the word out about the fire ants, getting folks to be aware, observe their surroundings, to make that connection that if they are getting stung by ants, then that’s something they should be reporting,” Fukushima said.

It only takes a few minutes to test for little fire ants. The procedure includes smearing a tiny bit of peanut butter, or mayonnaise if peanut allergies are a concern, on several thin strips of cardboard and placing them in shady places in the yard.

After 45 minutes, collect the samples with ants; place them in a plastic bag labeled with a name, address and contact information; and freeze for 24 hours to kill the ants.

“We are really pushing that message that Maui still has a chance to beat little fire ants,” Fukushima said.

Visit stoptheant.org to learn more about collecting ant samples and request a free ant collection kit. Mail samples to MISC at P.O. Box 983 in Makawao, HI 96768.

For more information or to make reports, call (808) 573-6472 or email miscants@ hawaii.edu. Reports can also be submitted through 643PEST.org.

* Dakota Grossman can be reached at dgrossman@mauinews.com.