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Little Fire Ants: A Growing Threat to Hawai‘i’s Agriculture

Posted on Sep. 1, 2025  /  Best Practices, Business Tips, Invasive Species, Nursery, Plant Pests, Arboriculture  /  Subscribe 0

By: Serene Gunnison

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Little fire ants (LFA), Wasmannia auropunctata, may be tiny, but their impact in Hawai‘i is anything but. LFA invades wherever present, taking over homes, fruit trees, gardens, and even commercial farms with ease. Known for their painful stings and large colonies, LFA have the potential to deal a heavy blow to the islands’ ecosystem and economies, and local agriculture and food production may feel the sting most acutely. Fortunately, early detection and rapid response are the best defenses against these mean little pests—whether protecting your home or preventing establishment island-wide. 

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Only about half the size of a sesame seed, these wee ants form dense supercolonies that spread across the landscape, invading acres of land from the ground to the treetops. In Hawai‘i’s environment, LFA colonies may have up to 20,000 ants per square meter. Densities of this magnitude create a cascade of complex challenges for Hawai‘i’s growers.

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Figure 1. About half the size of a sesame seed, little fire ants form dense colonies that invade acres of land, from the ground to the treetops.  Photo credit: Zach Pezzillo.

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Electric, painful stings are the most tangible impact of little fire ants. LFA are notorious for raining down on farmers harvesting fruit trees. Their burning stings leave welts that can last for weeks, making farm work miserable—if not impossible. Animals are often affected by LFA infestations as well. Stings in the eyes can cause blindness in pets, poultry, and even farm animals. LFA drives out beneficial insects, including native pollinators, and promotes aphids and scale insects by “farming” them for honeydew—a sugary secretion that the ants love to eat.

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One would think they’d know if their property had LFA. How hard could it be to miss a supercolony of stinging ants? But these mini menaces are stealthy. LFA can go undetected for months or even years. By the time stings are noticed or crops are compromised, the infestation may already be well established. The good news? There’s help available. 

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Figure 2. Little fire ants collected in a vial during a survey. Regular surveying is key to detecting new infestations early and preventing their spread. Photo credit: MISC.

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The first step is collecting and submitting samples of ants. Request a free test kit at stoptheant.org, or you can whip up a DIY test. All you need is a popsicle stick, peanut butter, and a Ziploc bag. Smear a thin layer of peanut butter on the popsicle stick and leave it in a shady spot in your yard for 30 minutes to an hour. Any ants in the area will be attracted to the peanut butter. Freeze the bag to kill the ants, then send it off to your local invasive species committee or Hawaii Ant Lab for identification (follow island-specific guidelines on stoptheant.org). Since LFA are adept hitchhikers, it’s good practice to test your property for ants every time you bring home new plants or landscaping materials. On Maui, community members have reported 80 percent of all little fire ant infestations—underscoring not only the importance of routinely testing your property but also community awareness.

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Finding LFA on your property or farm is never good news, but it can be managed—and even eradicated—with proper treatment. But the word ‘treatment’ can make people nervous. Few welcome the idea of chemical intervention around their food crops. Fortunately, there are non-toxic methods that can be safely used in agricultural settings. One such tool is methoprene, a synthetic hormone that targets the ants’ biology. Used by invasive species crews as part of an integrated approach, methoprene is an insect growth regulator that disrupts the ants’ ability to reproduce. While it’s not always the only method—many infestations also require the use of traditional pesticides—methoprene plays a key role in long-term colony collapse that leads to eradication from your home. 

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Figure 3.  Maui Invasive Species Committee field crew mixes LFA ‘bait:’ methoprene, beef liver, and soybean oil. Photo credit: MISC.

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But exactly how does methoprene work? Additionally, will it affect the insects that benefit farms and gardens? Ants need to consume methoprene for it to be effective, but on its own, it’s not very appetizing. To make it more tempting to ants, it is mixed into a bait that typically consists of soybean oil and a protein such as beef liver or peanut butter. Ants are among the few insects in Hawai‘i that seek protein, making the bait ant-specific. Other insects, such as butterflies, bees, spiders, and beetles, are generally not drawn to fatty, protein-rich foods and are unlikely to consume the bait. Once the ants feed the bait to their queen, she will no longer lay viable eggs. In a few months, the workers will die of old age, and the colony will collapse.

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While little fire ants are widespread on Hawai‘i Island, preventing island-wide establishment is still possible on Maui, O‘ahu, and Kaua‘i. Keeping the islands free from LFA relies not only on methoprene but also on an engaged community—reporting stings, allowing property access for surveys, and participating in treatment efforts. 

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Figure 4. Little fire ants are widespread on Hawai‘i Island, but control or eradication may still be possible on other islands. Photo credit: Melody Euaparadorn. 

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Backyard fruit trees are an integral part of life in Hawai‘i, and small farms play a critical role in reducing our dependence on imported food. Strengthening food security in Hawai‘i means preventing the spread of LFA. While early detection and rapid response remain the most cost-effective solution, tools like Tango offer a safe, science-backed path forward. You can help stop the spread of little fire ants in Hawai‘i. Collect and submit samples of ants from your property yearly and when you purchase new plants. Request a free test kit at stoptheant.org. With your kōkua, we can safeguard our farms, environment, and way of life. 

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Serene Gunnison, Social Media and Outreach Assistant, Maui Invasive Species Committee

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