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

By: Serene Gunnison

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. 

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.

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.

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.

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. 

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.

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.

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. 

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

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.

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. 

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. 

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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To Grow or not to Grow: Native Alternatives to Invasive Plants in Hawaii Landscaping

By: Darcy Yogi

About 90% of invasive plants in Hawaiʻi were intentionally imported for agriculture, forestry, and horticulture. Many of these invasive plants are objectively beautiful, but unfortunately, they can become a nightmare in our forests when they escape yards. That’s when the Big Island Invasive Species Committee (BIISC) comes in to help keep the worst invasives out of our high-priority native forests and to prevent new invasives from spreading across Hawaiʻi Island.

Did you know, it is legal to sell, cultivate, and import more than 99% of the world’s 250,000 flowering plants to Hawaiʻi? Therefore, BIISC has to work really hard to provide outreach to the public, so they can make informed buying decisions. A big component of that work stems from the Hawaiʻi-Pacific Weed Risk Assessment (HPWRA), which is a peer-reviewed vetting process for assessing the invasion risk of non-native plant species. Using the HPWRA scores along with field observations, BIISC can prioritize which invasive plants to focus our efforts on. 

If high-risk plants are being sold in local nurseries and garden stores, then BIISC will assess whether or not to add them to the No Grow! List. We encourage the public to please avoid buying the plants highlighted in this article and instead select one of the native plant alternatives provided. You can learn more about any plant at plantpono.org. Remember, once a No Grow! plant is put in the ground, it can be nearly impossible to contain it from spreading. 

Each No Grow! plant has particularly harmful invasive traits: 

● Shade-tolerant

● Produce viable seed that is dispersed by animals, water, and/or wind

● Prolific seed producer with seeds lasting more than a year

Autograph tree |  HPWRA Score: 9[1] 

Figure 1. Autograph Tree (Clusia rosea). Photo credit: Forest & Kim Starr. Retrieved at StarrEnvironmental.com

Native to the Caribbean, the autograph tree (Clusia rosea) thrives in Hawai‛i’s climate. First documented here in 1934, this species remains a commonly used landscaping tree. It quickly escapes cultivation, where it can epiphytically strangle other host trees and colonize gutters. When well-established, autograph trees can form dense thickets, effectively shading out other species. This tree reaches reproductive age in less than three years, and more than 1,000 bird-dispersed seeds are produced per square meter every year. Its epiphytic growth, aerial roots, and poisonous sap make controlling this plant extremely difficult.

Suggested native plant substitutes: Kou (Cordia subcordata), Milo (Thespesia populnea), Hau (Hibiscus tiliaceus).

Night-blooming jasmine  |  HPWRA Score: 17[2] 

Figure 2. Night-blooming jasmine (Cestrum nocturnum). Photo credit: BIISC

Cestrum nocturnum is a highly invasive plant that has been spreading in native koa forests and preventing new native seedlings from establishing. Therefore, this invasive has been able to thrive far away from its probable origin near human residences. Birds, attracted to the white pea-sized fruit, consume the fruit and can fly to distant places before eventually pooping out the invasive seeds. Night-blooming jasmine’s sweet fragrance can hide its toxic and hazardous qualities.

Suggested native plant substitutes: Alaheʻe (Psydrax odorata), Nāʻū (Gardenia brighamii), Hōʻawa (Pittosporum hosmeri)

Asparagus fern  | HPWRA Score: 15[3] 

Figure 3. Asparagus fern (Asparagus densiflorus). Photo credit: Forest & Kim Starr. Retrieved at StarrEnvironmental.com

Asparagus densiflorus is a highly invasive, shade-tolerant perennial plant. Once established, this plant will be difficult to eradicate with its extensive root structure and the ability to regrow from even the smallest root left behind. Its needle-like leaves and thorns further complicate control efforts. In Hawai‛i, this species escaped cultivation and now invades low-light habitats and native forests. It has been able to spread far and wide with its bird-dispersed seeds and vegetative tubers. Unfortunately, even though this species is listed as invasive in 9 countries, it's still found for sale and prominently displayed in landscaping.

Suggested native plant substitutes: Palapalai (Microlepia strigosa), ʻUkiʻuki (Dianella sandwicensis),  ʻIlieʻe (Plumbago zeylanica)

Tasmanian tree fern  |  HPWRA Score: 13[1] 

Figure 4. Tasmanian Tree Fern (Dicksonia antarctica) Kew-Gardens. Photo credit: BIISC.

Dicksonia antarctica is an invasive tree fern that’s native to Australia and Tasmania. While it thrives in a broad range of climates, the higher elevation wet forests of the Hawaiian Islands are most at risk. Similar to the invasive Australian tree fern, this species’ shade tolerance and long-distance spore dispersal combo is a dangerous combination for our native forests. It is slow-growing and takes many years to reach reproductive maturity. However, when it does make fertile spores, it does so in massive quantities. A single frond produces as many as 750 million viable airborne spores! Its ability to rapidly spread via wind means there are few barriers to the dispersal of this species.

Suggested native plant substitutes: Hāpuʻu (Cibotium glaucum), Loulu (Pritchardia hillebrandii), ʻĒkaha (Asplenium musifolium)

High-risk Medinilla species  |  HPWRA Score: 8[5] 

Figure 5. Medinilla cumingii. Photo credit: Forest & Kim Starr. Retrieved at StarrEnvironmental.com

Many plants in the Medinilla genus and Melastomaceae family are weedy and extremely invasive in Hawai’i. The seeds are easily dispersed by birds, water, and unintentionally through human activity (i.e., muddy boots/vehicles). Seeds, propagules, and clippings are often shared and sold due to their beautiful flowers and attractive foliage. However, these disturbance-adapted plants can produce more than 1,000 persistent seeds per square meter every year. Destructive to native habitats, these plants are very aggressive - shading over, crowding out, and smothering surrounding vegetation. Two particular species in this genus to avoid include Medinilla magnifica and Medinilla cumingii. 

Suggested native plant substitutes: Māmaki (Pipturus albidus), ʻAkiohala (Hibiscus furcellatus), Kokiʻo keʻokeʻo (Hibiscus waimeae)

Barbados gooseberry  |  HPWRA Score: 13[6] 

Figure 6. Barbados Gooseberry  (Pereskia aculeata ). Photo credit: BIISC

Pereskia aculeata is capable of adapting to a variety of environmental conditions. Viable seeds are spread by water, birds, and humans in the horticultural trade. This sprawling shrub spreads rapidly to form dense, thorny, impenetrable thickets that effectively smother other vegetation. Stems and detached leaves stay alive and can form roots months after removal from the parent plant. Extreme thorniness and vigorous growth from plant fragments make control difficult. Barbados gooseberry is a target species for eradication on Hawaiʻi Island. If encountered, please contact BIISC for free removal.

Suggested native plant substitutes: Pāʻūohiʻiaka (Jacquemontia ovalifolia), ʻŪlei (Osteomeles anthyllidifolia), Maiapilo (Capparis sandwichiana)

Shrubby Dillenia  |  HPWRA Score: 11[7] 

Figure 7. Shrubby Dillenia (Dillenia suffruticosa | Plant Pono). Photo credit: OISC.

Dillenia suffruticosa is an invasive flowering shrub native to the tropical climates of Borneo and Sumatra. In Oʻahu, shrubby Dillenia forms thickets from lowland moist valleys to ridge-top forests. Likely, it was introduced as a botanical specimen at Hoʻomaluhia Botanical Garden, where the first seedlings were found growing in a disturbed area just outside the grounds. This invasive plant makes more than 1000 viable seeds per square meter per plant! Attracted to the red seeds, non-native birds eat and disperse them around our forests. 

Suggested native plant substitutes: Maʻo hau hele (Hibiscus brackenridgei), Pāpala kēpau (Pisonia sandwicensis), Kamani (Calophyllum inophyllum).

Bandicoot berry  |  HPWRA Score: 4[8] 

Figure 8. Bandicoot berry (Leea indica). Photo credit: Ahmad Fuad Morad.

Leea indica is a small tree with an extensive native range in tropical Asia. Imported by Joseph Rock and planted in the Lyon Arboretum in 1931, the seedlings were documented spreading only 12 years later. Today, there are naturalized populations on Hawaiʻi Island and possibly Oʻahu. Bandicoot berry thrives in the understory, where it produces many bird-dispersed purplish-black fruit. BIISC always recommends avoiding this plant in the store and trying a pono plant instead.

Suggested native plant substitutes: Kōpiko (Psychotria hawaiiensis), Neneleau (Rhus sandwicensis), ʻŌhiʻa ʻai (Syzygium malaccense)[1] 

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Darcy Yogi lives in Hilo, HI, and works as the Invasive Plant Prevention Technician for the Big Island Invasive Species Committee. She helps to support the Plant Pono program, which focuses on preventing the spread of invasive plants and insect pests within the nursery trade on Hawaiʻi Island.

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Peperomia sandwicensis, Ekahanui, a new native indoor plant with interesting leaf venation

By: Orville C. Baldos

Peperomias are very popular as houseplants because they are easy to care for. Many species and cultivars are sold in grocery stores, nurseries, and big box stores across Hawaii. But did you know that Hawaii is home to 23 endemic and 2 indigenous species of peperomia? Some of these species have colorful leaves and stems that make them very ornamental. 

Indoor plant research conducted at UH Manoa for the past eight years has identified several native peperomia species that can thrive as indoor plants. Among the tested species, Peperomia sandwicensis showed the most tolerance to indoor light conditions. In 2021, Peperomia ‘Palikea’ was introduced as a compact selection for small spaces [1]. In this article, we introduce ‘Ekahanui’, a larger selection with contrasting veins on its leaves. 

Figure 1. Peperomia sandwicensis ‘Ekahanui’ in a 3.43-inch diameter ceramic pot. Photo by Orville Baldos.

‘Ekahanui’ was collected as a stem cutting by botanist Joel Lau in West Oahu. A plant grown from the stem cutting was maintained at the Harold Lyon Arboretum and then moved to the Magoon Research Facility for propagation (e.g., cuttings and tissue culture) and evaluation. In 2022 and 2023, six-month indoor light trials were conducted under low (350 lux), office (750 lux), and high light (5000 lux) conditions. Results of the trial indicate that ‘Ekahanui’ can maintain an attractive appearance under office (750 lux) and high light (5000 lux) conditions. In 2024, ‘Ekahanui’ was officially described and released [2].

‘Ekahanui’ is a bigger plant compared to ‘Palikea’. Plants can grow up to 8 inches high (excluding flower spikes). Stems are hairy and can be upright to floppy with few branches. Stem color can range from red-purple (RHS 59A [3]) to grayed orange (RHS 166A). The average internode length (i.e., length between nodes/leaves in the stem) is 0.9 inches. Leaves are 0.6 to 1 inch wide and 0.7 to 1.3 inches long. The upper leaf surface has no hairs, is dark green (RHS N137A) with light green (RHS 138C) veins (3 to 5 veins prominent) and secondary veins that form a netted pattern. The lower leaf surface is hairy and red-purple (RHS 59A). Veins may sometimes appear light green (RHS 138D) or pinkish (RHS N170D). Flower spikes are floppy and can grow very long (up to 10 inches) on the stem tip or the side of the stem. 

Figure 2. ‘Ekahanui’ (left) and ‘Palikea’ (right) plants side-by-side. ‘Ekahanui’ has a more elongated growth than ‘Palikea’. It also has bigger leaves that possess very prominent leaf venation. Photo by Orville Baldos.

‘Ekahanui’ can be propagated from stem and leaf cuttings. Stem cuttings produce plants the fastest (two to three months) while leaf cuttings may take longer. Applications of rooting hormone (3000 ppm indolebutyric acid) prior to sticking can improve root length and root numbers. Cuttings may be planted in moist calcined clay or succulent potting medium. Allow cuttings to root under bright indirect light or under cool white LED shoplights (placed 11 inches above the cuttings). Rooting takes about a month. Once the roots form, plant cuttings in a well-draining potting medium or succulent mix. Top dress plants with slow-release fertilizer.

‘Ekahanui’ grows best under bright indirect light with or without air-conditioning. To promote branching, shoot tips can be pinched. Flower spikes and floppy stems can be pruned off to improve appearance. In terms of watering, allow the soil to partially dry in between waterings and avoid standing water at the bottom of the pot. Watch for thrips, root mealybugs, and scale insects. Managing these pests will prevent stunting, severe defoliation, and plant death.   

Figure 3. Pinching 1 – Pinching plants twice at 1 and 2 months after propagation enhances the branching of ‘Ekahanui’. Photo by Orville Baldos.

Figure 4. Pinching 2 – Six-month-old plants pinched at 1 and 2 months after propagation from stem cuttings. Photo by Orville Baldos.

Figure 5.  ‘Ekahanui’ in a 6-inch pot, growing for 5 months indoors at the UH Manoa Law Library. Photo by Orville Baldos. 

Contact Orville Baldos (e-mail: [email protected]) for inquiries on plants or stem cuttings of Peperomia sandwicensis ‘Ekahanui’.  

References: 

3. Royal Horticultural Society. 2007. Royal Horticultural Society colour chart. RHS. London, UK.

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Orville Baldos, Associate Researcher in Sustainable Ornamental Production, Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa. Contact Orville Baldos (e-mail: [email protected]) for inquiries on plants or stem cuttings of Peperomia sandwicensis ‘Ekahanui’.  

 

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LICH Recognized with National Communications Award

By: Alberto Ricordi, Hannah Lutgen, Karen Smith, LICH Newsletter Team

The Landscape Industry Council of Hawaii (LICH) Newsletter received the “Third Place Outstanding Multi-part and Image-based Communications Award”, presented at the 2025 ASHS Conference, July 28 - August 1, 2025, in New Orleans, Louisiana.

LICH is the largest landscape association in the state. In 2023, the bi-monthly printed publication (formerly the Hawaii Landscape Magazine) transitioned to a digital platform to extend reach, improve efficiency, and enhance delivery and access to the newsletter and articles. In collaboration with LICH, University of Hawaii CTAHR extension agents serve as editors: Hannah Lutgen is the current lead editor, Alberto Ricordi is the co-editor, and Russel Galanti served as lead editor of the Hawaii Landscape Magazine until August 2023. The newsletter features science-based, educational, and informative articles representing a broad range of sectors in the landscape and ornamental plant industries—including commercial, private, government, academic, arboriculture, landscape architecture, conservation groups, and other related businesses—creating a multi-faceted publication. The editors work closely with LICH staff member, Karen Smith, to solicit, review, edit, plan, and upload content.

The newsletter's reach multiplies with each mailing. Until January 2025, the newsletter boasted 700 subscribers; an average 1,200 hits per newsletter; and 4,000 blog/archive hits annually. More recently, the newsletter had 2,785 hits in March, 3,252 hits in May; and 4,461 hits in July, showing a steady growth in reach.

Mahalo to all authors who submit engaging articles, and to the editors and staff for your commitment to Hawaii's Landscape Industry! If you are interested in contributing to the newsletter or submitting an article, please contact Alberto Ricordi at [email protected] and Hannah Lutgen at [email protected].

Figure 1. UHM CTAHR Extension Agent Alberto Ricordi received the award on behalf of the LICH Newsletter team. Photo by: Tiare Silvasy, UF/IFAS Extension Hillsborough County. 

Figure 2. LICH Newsletter “Third Place Outstanding Multi-part and Image-based Communications Award”, presented at the 2025 ASHS Conference, July 28 - August 1, 2025 in New Orleans, Louisiana. Photo credit: Alberto Ricordi.

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Alberto Ricordi, Hannah Lutgen, Karen Smith, LICH Newsletter Team

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MemberTalk

This month we reached out to our most active members and asked them questions about the conference. They shared their thoughts on questions like "why do you attend the LICH conference every year?  What sessions interest you the most? Is there anything new this year you are anticipating more than others? 

Mahalo to Brandon, Christy, Hannah and Larry for participating!  If you would like to contribute in future issues, let us know.  Email  our editors at [email protected] 

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Conference News

This year’s tradeshow is shaping up to include the most comprehensive list of green industry vendors in years.  With 25+ exhibits and a prize-filled pau hana we, once again, expect the end of day networking hour to be a highlight of the event.

If you have team members who don’t need CEU credit and can’t afford a full day off the job, we invite you to secure half-day tradeshow passes.  With entrance open any time after 1pm, your team can still participate for a much lower rate.  Tradeshow tickets are available through September 18, beginning at $50.    

Some of the prizes confirmed include:

 

Mahalo to our participating exhibitors:

 

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Hawaii Landscape magazine is an educational, newsletter that reaches Hawaii’s landscape industry professionals.  With a diverse industry readership across the state of Hawaii and beyond, our readers represent some of Hawaii’s most active and influential landscape professionals.  As the “Voice of the Green Industry” Hawaii Landscape readers appreciate the authoritative voice on everything from design of great landscapes to irrigation technology, native plants, conservation, community service, small business management, book reviews, machine & tool tips, herbicide & pesticides, invasive species, certifications, and industry events.

To learn more visit https://hawaiiscape.com/Advertising_Information

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