Sunday, April 21, 2019

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.


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.
  • 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.

1 comment:

Norris said...

Comment I received via email from someone who lives on a relatively recent lava flow with relatively little vegetation:

Nice presentation in the way you suggest a post industrial problem that can be addressed pre collapse, while there is still time to develop a biological control. I must say that my black ants have been moving into the territories of the fire ants. It seems like removing 2- 100 gallon water troughs caused a collapse of a large area of LFA's and the crazy and other black ants moved in.