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Tiny invasive ant looms large as threat to the islands

by Rob Parsons

October 11, 2007

The little fire ant, found on the Big Island in 1999, poses great risks to humans, animals, and the future of agriculture in Hawai'i. While the stinging insect has not become established on Maui, recent Circuit Court testimony regarding the Hawai'i Superferry revealed the likelihood of introductions between islands, and the shortcomings of Department of Agriculture's ability for rapid response and eradication of transported pests.

Native to Central and South America and the Caribbean, the little fire ant (wasmannia auropunctata) is a mere sixteenth of an inch long-about as long as a penny is thick. Yet it packs a painful stinging bite when disturbed. The sting raises large, red welts, which may last for days, with intense itching. Like many other Hawai'i invasive pest species, it is likely that it hitchhiked over in shipped nursery stock.

Originally detected in the Puna area eight years ago, the little fire ant has since been identified at more than 50 infestation sites. Kauai eradicated a colony which appeared in 1999, only to find more in the Kalihiwai area in 2004. A Cooperative Extension Service Alien Pest Alert from May of that year stated, "Containment actions are being taken, but limited resources and personnel, and pesticide label use restrictions, have made it difficult to eradicate all the infestations there."

Such is the case, in general, for alien pest eradication efforts statewide. Incoming passengers and freight on route to Hawai'i are not afforded the same degree of inspection as those leaving the state. Noble efforts by Invasive Species Committees on each island are limited by funding appropriations. The Hawai'i Department of Agriculture hasn't come close to filling the nineteen inspectors and three dogs recommended in a 2002 risk assessment at Kahului airport.

DOA's Plant Quarantine Branch manager Carol Okada testified recently in Maui Circuit Court, regarding an injunction to keep the Superferry in port until mandated environmental studies are complete. She stated, "[Invasive pests] will continue to move as it's doing now. It's just a matter of time. ...As long as people move and cargo moves, invasive species will move."

"We don't expect Superferry to be able to detect pests or disease on a plant, that is our job," she said.

But, the diminutive little fire ant, barely detectable to the human eye, is unlikely to be successfully screened, even by trained inspectors. There are now more than fifty verified infestation sites covering several hundred acres in Puna, Hilo, up the Hamakua coast, down to Kalapana, and to Mountain View. But Tommy Thompson, researcher with the UH College of Tropical Agriculture says, "It's way more than that," noting that there are pockets of ant colonies, "all over Hilo, in many neighborhoods."

Thompson has been testing to see what registered pesticides and baits can help control the little fire ant. Currently, they use Amdro, which he says, "will knock them down, but not out." Without ongoing treatment, they will bounce back to their original numbers within five to six weeks. Amdro, says Thompson, was also developed for a different kind of ant--and in dry areas such as Texas--not in rainy Hilo and Puna.

Moreover, this ant is "unbelievably adaptive," says Thompson. Rather than spot colonies, there tends to be blanket coverage in infested areas. And, these tiny ants are arboreal, so pesticide baits aren't effective where they reside in trees, often underneath bark, moss, or lichen.

Workers brushing branches in macadamia nut or fruit orchards may find ants dropping on them, stinging them repeatedly. The little fire ant, "wiped out the coffee industry in the Galapagos Islands," says Thompson. It presumably has not yet been carried to the Kona side of the Big Island, known for its world famous coffee, but it may just be a matter of time.

Even if there were an intra-island quarantine to prevent transport of plant materials from Hilo to Kona, the ant might find other ways. Thompson reported finding a single macadamia nut with a tiny hole bored in it. Inside was an entire functional colony, with queens, workers, and brood.

"The biggest thing right now is that we don't have the tools necessary to fight it," said Thompson. He described an Australian pesticide product called Xtinguish that is not currently registered for use in Hawai'i. Baited with insect pupae, lipids, and proteins, the product fits in a standard caulk gun for easy dispersal. It has been used elsewhere in the Pacific where this ant has caused big problems, such as Papua New Guinea, New Caledonia, and the Solomon Islands. In a paste form, it is more water resistant, and thus better suited to East Hawai'i's wet climate.

The New Zealand model of inspections and rapid response is looked upon as the gold standard of invasive species control. New Zealand successfully eradicated an introduced infestation of a larger, even nastier relative--the red imported fire ant. But Hawai'i has yet to take the drastic measures to protect our resources that New Zealand has done, with the accompanying funds to insure a higher level of effectiveness.

The little fire ant may be confused with another stinging variety, the tropical fire ant. This more aggressive species, three times larger, has been in Hawaii for probably a hundred years. But it doesn't have the unicolonial characteristics of the little fire ant, and is deemed less of a threat than its tiny cousin. It has not been detected east of Kahului, or in Upcountry Maui.

"Ecologically, this is a disaster waiting to happen," says Thompson. Right now, the range of the little fire ant is limited to non-pristine eco-systems. Limitations of altitudes are not yet known. Should the range spread to native eco-systems, Hawaiian insects, spiders, and birds could all be imperiled. "These things are bad news to whatever gets in their path." Thompson warns.

Little fire ant stings are also known to harm animals, including pets and livestock; multiple stings in the eyes can cause blindness in pets or even the death of newly born small animals.

Thompson is concerned for native bird populations in Lower Puna, where the ant colonies are already found. Biologists have recently tracked two species of honeycreepers, the amakihi and elepai`o, whose populations have rebounded in this area. Probably, they have developed a resistance to avian malaria, which is spread by mosquitoes and has weakened and decimated native bird populations statewide. Thompson believes that spreading colonies of ants throughout trees in the area may threaten these resurgent bird populations, attacking nests and their hatchlings.

United States Geological Survey biologists Lloyd Loope and Forest and Kim Starr did a Maui island survey of ant species--specifically looking for the little fire ant. None were found. They used a standard protocol of using peanut butter baited chopsticks to collect and identify the ants, especially in high risk areas such as new landscape plantings within new developments.

The same methodology is used by Department of Agriculture inspectors for shipments from plant nurseries from the Big Island. In one case, ant-infested plants arrived on Maui, were detected and refused. In another case, the peanut butter bait helped reveal the ants before the shipment was made.

Sometimes it seems that there's trouble in paradise almost anywhere you turn. Threats to our native ecosystems, tourist and agriculture economy, and to our quality of life seem overwhelming--straining our resources and our ability to keep up with them.

The recent appearance on Maui of the nettle caterpillar, which also packs a painful sting, reveals our vulnerability to introduced pests on incoming plant materials. The Department of Agriculture's response to this new pest has been far less than the all-out blitzkrieg necessary for total eradication.

Yet, with alien invasive species, the adage "An ounce of prevention is worth a pound of cure" seems especially apropos. Measures of prevention may not be limited to the dollars we allocate, but may extend to insistence upon compliance with our environmental laws, to properly assess risks before they occur and multiply.