Paradise or hell?—Hawaiian future depends on little fire ant biocontrol

The Scourge

Those who haven't lived with little fire ants (LFAs, Wasmannia auropunctata) may not be able to imagine the hell they bring when unchecked. Their stings burn like fire for up to hours, leaving angry welts which can itch and irritate for days. The ants readily sting when trapped against flesh, making sitting on a couch or rolling over in bed perilous in an infested home. Painlessly climbing trees for fruit or fun requires an armor of clothing carefully secured so as not to press exposed skin against ant-coated bark.

The ants don't cling to surfaces well. Anything which shakes branches, including a strong wind, harvesting fruit, or pruning or cutting a tree, brings down a barrage of confused six-legged pressure-trigger venom grenades. Though not aggressive—they're content to just crawl around once they land—if they get caught in the fold of an elbow, or in an armpit, or where a collar or bra or waistband or sock meets flesh, the stinging and the pain begin. In a tropical environment, bundling up in a full layer of tightly cinched clothes is its own mini-hell; your choice when working infested land is between the frying pan and the fire.

Blinded cat

When LFA's get trapped in eyes, their stings can permanently damage corneas of non-humans and sometimes of humans. These corneal lesions, also known as tropical keratopathy, impair vision and can even cause blindness.

LFAs are a "tramp species," readily colonizing new tropical and subtropical territory with the aid of human transportation. Native to South America, they're now found in Central America into Mexico, in Africa, on many Pacific and other tropical islands, and in Florida and Texas. Global warming will likely increase their range.

Here in Hawai'i, they displace all other ant species and form an infernal monoculture, densely covering the ground and nearly every plant surface. I have a disability and often fall down; in doing so, I frequently receive a dozen bites at once.

The "Little" is perhaps an understatement; at 1.5mm (1/16") long, they could just as well be named Tiny Fire Ants. Reproductive colonies can live in a single macadamia nut shell, and have been found between the threads of a mason jar with the lid on. It's all too easy to inadvertently seed a new infestation by moving coconuts, mulch, and potted plants—or canning jars which appear sealed. Even without human aid, the LFA front expands up to hundreds of meters per year.

Intractable doom?

The East Hawai'i Master Gardener Program advises, pessimistically but realistically:

Unfortunately, once your property is infested with Little Fire Ants, you will probably never successfully eradicate them. The best you can do is to avoid bringing them onto your property in the first place and, if your property or home is infested, to manage their numbers.

That "management" depends entirely on commercial pesticide. Though many in my hippie region of Puna have trialed alternative, natural LFA deterrents and killers, nothing has worked reliably. Until I began living with LFAs, I unequivocally opposed chemical herbicides and pesticides, but I now make this one exception. Land work and daily life are just too miserable if the LFAs are allowed to spread unchecked.

But this chemical warfare is only a stopgap. When the ships inevitably stop bringing us products reliant on an unsustainable—meaning it won't be sustained—global system, then techniques dependent on imports will break down. Chemical suppression of fire ant populations is salve applied to ongoing burn damage from an unquenched fire. But upon winning relief from the immediate onslaught of LFAs, busy landowners, understandably, accept the chemical treadmill and are less motivated to seek out a long-term solution.

The best cure by far is prevention. Those living in clean areas at risk of infestation should take all necessary precautions to block introduction. I realize that hypothetical threats of never-experienced misery are only lukewarm motivators. If you're insufficiently impelled by LFA's status as one of the world's worst invasive species and by the horror stories of others, contact me about my "LFA tourist" package. (I'll send you to an infested property where you can roll around in the grass and imagine that as your future LFA-coated bed.)

With vigilance, it's not difficult to avoid introducing LFAs to your property. If neighbors are infested, disciplined poisoning of your borders and trimming of vegetative "bridges" will keep you clean. However, if you suffer a year or two of ill health and can't maintain your borders, or if a hurricane blows colonies across your land, you'll quickly find yourself defending only core living structures. Once the poisons become unavailable, you won't be able to defend even those.

Systemic problems never yield to personal solutions. Quarantining one's private patch of ground will only hold off the ants for so long. Their range in continental areas will ultimately depend on whether climate or other barriers block them from migrating. But uninfested islands can and should implement rigorous education campaigns and inspection routines to keep the LFAs out until the collapse of inter-island commerce minimizes the risk of introduction. If small infestations are discovered, they should be diligently and thoroughly eradicated.

That doesn't help those of us who've lost the chance for permanent exclusion. The good news is that, naturally, LFAs don't form a monoculture in their native range. They're presumably kept in balance by natural enemies. Even in their non-native Florida, they aren't huge pests once resident fauna strikes a balance following their initial invasion. The long-term solution for areas where LFAs remain serious problems is biological control.

Biocontrol

I used to feel gloomy about the post-collapse Hawai'i future being one of welt-covered, cowering humans drawing straws for who has to harvest food each day. But I gained hope from "The Little Fire Ant, Wasmannia auropunctata: Distribution, Impact and Control" by James K. Wetterer & Sanford D. Porter. They estimate "based on experience with finding, screening, and releasing phorid flies as biocontrol agents for Solenopsis fire ants" that a comprehensive biological control program for little fire ants would cost a mere "several hundred thousand dollars per year for 5-10 years."

Relevant paper excerpts:

Classical biocontrol agents may be the only hope for controlling exotic populations of W. auropunctata in areas where it is firmly established. A classical biocontrol agent is one that expands naturally and becomes permanently established without the need for further releases. The advantage of using classical biocontrol agents is that their benefits are widespread, permanent, and without cost after the agent becomes established.

One parasite of W. auropunctata has been identified, the eucharitid wasp Orasema minutissima (Mann 1918). Johnson (1988) and Heraty (1994) recommended further evaluation of Orasema wasps as potential biocontrol agents of pest ants. Several pselaphid beetles (Mann 1921, Park 1942) and a staphilinid beetle (Silvestri 1946) have been identified as symbionts in Wasmannia colonies.

In an attempt to discover additional natural enemies of Wasmannia, we recruited colleagues to inspect W. auropunctata colonies in Trinidad, Costa Rica, and Brazil (Porter & Wetterer, unpublished). From a total of 95 W. auropunctata colonies, a wide variety of organisms were extracted. Although no known parasites of W. auropunctata, such as eucharitid wasps, were identified, some associated organisms deserve additional attention, including gamasid mites and several unidentified fly larvae and microhymenoptera. Among the fungi, most were probably saprophytic, though Verticillium is possibly pathogenic. Determining the exact relationships of the organisms found in the nests will require much further study.

The fascinating paper "Specialized predation on Wasmannia auropunctata by the army ant Neivamyrmex compressinodis" explores an intriguing biocontrol possibility. It's unlikely to be deployed in Hawai'i, as people might be understandably reticent to introduce an army ant, but perhaps where other army ant species already live...?

Back to Wetterer and Porter, who sketch out a biocontrol research program:

1. Native populations of W. auropunctata should be carefully compared to exotic populations to determine if native populations are really less dense than exotic populations and what are the likely causes of any differences.
2. In order to find biotypes of natural enemies that are best adapted to attack exotic populations of W. auropunctata, researchers need to identify the original range of W. auropunctata auropunctata. Exotic populations of W. auropunctata auropunctata may be originally derived from only one population or from multiple populations. Ideally, DNA analysis of exotic and native populations should be used to identify specific source populations.
3. A thorough search for natural enemies would probably require several weeks to several months of efforts in each of several different areas. Furthermore, this search would likely require scientists with expertise in parasites and others with expertise in pathogens.
4. Several months to a year or more are often necessary to obtain permits to export and then more permits are needed to import the presumptive control agent for study in quarantine.
5. Once candidate agents are found, researchers would need to find ways to rear enough agents.
6. Conduct host specificity tests to determine whether the organisms were environmentally safe for field release.
7. Then, if results justified it, more permits and reviews are needed for field release.
8. Finally, researchers would need to release prospective biocontrol agents and monitor their survival, expansion, and impacts on W. auropunctata populations.

In short, a comprehensive biocontrol effort for W. auropunctata would probably require significant cooperative agreements between governments, conservation groups and scientific organizations concerned with the problem. Though difficult and expensive, classical biocontrol is the only likely long-term solution to the ecological ravages of exotic populations of W. auropunctata on tropical and subtropical islands.

Project leader needed

If Wetterer and Porter are correct in their financial estimate, it might only cost $5 million to fund a full biocontrol research program. That's insignificant next to the economic damage LFAs threaten to Hawai'i agriculture, tourism, and real estate. Many other governments also have a vested interest in controlling LFAs, so the money needn't even come solely from Hawai'i. I'm too busy stopping fossil fuels to lead a campaign for government funding of a biocontrol research program, but it should be relatively uncontroversial and straightforward:

• Contact the Hawai'i Ant Lab to discuss all this.
• Figure out where funding might come from for such a research project and who allocates the funds. This will guide the rest of the campaign, since all pressure should ultimately be directed towards these decision makers.
• Educate citizens about the the feasibility of a long-term biocontrol solution. Target areas already affected by LFAs.
  • Gather petition signatures to demonstrate popular support to decision makers.
  • Grassroots campaign to write and call decision makers in support of a biocontrol program.
• Contact environmental orgs, especially invasive species councils.
• Contact business associations and influential players potentially motivated to reduce threats to tourism, ag, nursery business, and real estate.
  • Hawai'i Farmers Union United
  • Hawai'i Department of Ag
  • CTAHR
  • ??
• Explore collaboration with groups and governments outside of Hawai'i which might contribute to biocontrol research.
• Work with sympathetic politicians where advantageous.
• If all else fails, infest the homes of unsympathetic politicians with little fire ants to give them incentive to find a solution.

It will take a lot of work to see this through, but success is entirely feasible. The sooner this push is started the better, since energy supply (and thus funding) will only get tighter in the future. This needs to happen while there's still available money and political & societal focus to pull it off.

If anyone is seriously interested in taking this on, I can provide some support, and probably muster some others willing to help if someone provides solid project leadership. Comment below or email me.

Blog to know: Tropical Self Sufficiency

A Puna, Hawai'i resident named Spencer has been experimenting for a couple of years with perennials in the tropics, and he's written up some excellent experience based species profiles. You'll find many of the species explored by Toensmeier's Perennial Vegetables, one of Spencer's inspirations. Some species are purely tropical, but many are familiar friends (or could become such!) of temperate permaculturists as well.

The site is loaded with information on propagation, growth, harvest, and use of perennials, in a combination of collated research and original discoveries. Multiple photos accompany each entry, usually including shots of the plants living in polycultures, with the surrounding species conveniently named as well. As the site title indicates, there's an emphasis on staple crops.

All in all, my kind of info-dense resource! Check out Spencer's site at Tropical Self Sufficiency.

Shading paths in Hawai'i

This post follows up on the concepts of my post Sun and Shade, Temperate vs Tropical, with some quick thoughts on paths. Ideally, Hawaiian paths would be shaded in the summer for protection of humans from the sun and maximum photosynthesis, but more open in the wet winters to prevent too much mud and muckiness.

Paths running east-west could have large trees planted on the north side to overhang the path enough to provide shade from the spring to fall equinox, while allowing winter sun to enter from the south.

Paths running north-south could be treated in one of a few ways:

• Compromise plantings of hedges or trees at wide enough spacings or with relatively sparse canopies to provide incomplete summer shade and incomplete winter sun.
• Coppiceable plantings of quick-growing trees or tall hedges, cut in the winter and allowed to grow through the summer. This would work well with N-fixers to provide mulch easily transported along the paths to desired destinations.
• Deciduous plantings (such as kapok) providing the standard summer shade/winter sun service.

Sun and shade, temperate vs tropical

May has arrived in Hawai'i, and for the next two months, the sun will shine on us from the north. Huh? From the north? Doesn't that only happen in locales south of the equator, like in Australia?

(The rest of this post assumes a northern hemisphere location, expecting the sun to shine from the south.)

I knew the sun travels at a higher angle in the tropics, and I knew that in temperate climate summers the sun rises and sets in the north. But until shortly before moving here, I had no idea that for part of the summer, our sun never even crosses over to the south. This is the case everywhere within the tropics; on the margins, the Tropic of Cancer and the Tropic of Capricorn, the sun is directly overhead at noon on June 21st. Closer and closer to the equator, the sun spends more and more time in the north, with part or much of the summer never even seeing the sun shine from the south. This makes for a bizarre solar chart!

Combined with greater tropical sun intensity and temperatures, this necessitates different strategies for shading structures. Standard temperate tricks for winter sun/summer shade don't directly apply; properly sized and angled eaves, deciduous vines on a south arbor, and a deciduous tree to the southwest don't help when the midday sun is directly overhead or shining from the north. I'm no expert at this for Hawai'i, let alone qualified to generalize to the rest of the tropics, but here are my observations and thoughts so far. Some of this also applies to plant interactions and light into understories.

• It's not nearly as important to maximize sunlight in the winter. Though it helps combat the mildew and mustiness we encounter in this super-rainy part of Hawaii, we don't need the sun for warmth. It's OK to compromise a bit on winter sun access.
• We don't need to design for morning sun. Unlike temperate climates, where it can still be chilly on spring, fall, and even summer mornings, we don't need a quick boost of morning sun to warm us up.
• We don't have a large choice of trees that drop their leaves in the winter, and I have even less knowledge of exactly when they drop and regrow leaves, or whether they stick to a consistent schedule driven by the sun (rather than, for example, rainfall.)
• We don't have many deciduous vines. The best I've found so far are the yams (Dioscorea spp.), of which the winged yam (D. alata) and air potato (D. bulbifera) seem most useful. They die down to the ground in November or December, and resprout in March or April, growing quickly to potentially cover a large area by early to mid summer. These may work well growing directly on top of the roof, or on a framework trellised over the roof.
• Rather than a tree to the southwest, we want trees to both the east and west, or the northeast, north, and northwest. Ideally we'd have full tree canopy directly over the structure and maybe a bit to the south. This would provide full winter sun with maximum summer shade. An ideal tree, in order of priority:
  • Has a broad, spreading canopy of known width so we can plant it reasonably far from the structure and not have to prune too much
  • Produces some useful yield of fruit or leaves suitable for zone 1, perhaps harvestable from the roof
  • Doesn't drop limbs or large fruit on the roof (or loud hard nuts on a metal roof)
  • Grows to a useful size quickly, then slows down
  • Doesn't drop much leaf litter, especially if the roof is used for rainwater catchment
  • Lives a long time
  • Does not fix nitrogen, since we'll already provide ample urine to the area

I need to do more research on possible tree candidates, and probably some experimentation to figure out which will grow well on our particular site once we settle somewhere. I'll share those thoughts once I've developed them further!