Annual Damages from Little Fire Ant Could Be $170 Million on Big Island Alone

posted in: Invasives, September 2013 | 0

If efforts to control the little fire ant (LFA) on Hawai`i stay as they are, the island could see damages of nearly $170 million a year, as well as 33 million sting incidents a year. That’s according to University of Hawai`i planning student Mike Motoki, a presenter at the 21st annual Hawai`i Conservation Conference held recently in Waikiki.

The bright orangey-red ants – Wasmannia auropunctata — are native to Central and South America and form large colonies on the ground and in trees. In addition to Hawai`i, they have also invaded Tahiti, the Galapagos Islands, and other parts of the Pacific. Their burning stings can send you running to the drugstore for a pack of Benadryl.

Using a model developed by scientists at UH, Motoki has been able to estimate the potential economic harm and number of sting incidents that are likely to occur with varying levels of ant management. He looked only at impacts to six sectors (nurseries, agriculture, residential, lodging, parks, schools, and other). He did not assess the potential threats to native species or the costs associated with pets blinded by ant stings.

Eradication, he found, wasn’t really worth the cost. His model showed that it would cost about a billion dollars to eradicate the ants from Hawai`i island, where they have steadily spread since a state entomologist discovered them there in 1999.

And even if you spent all that money, says Hawai`i Ant Lab manager Casper Vanderwoude, “you may or may not succeed.”

The ants, as tiny as crumbs, are notoriously persistent. Eradication is “probably not an economic thing to do” given the cost, Vanderwoude told Environment Hawai`i. Motoki recommended something in between the status quo and total eradication. Spending about $70 million on mitigation and the prevention of an expanded ant range over the next ten years could result in a significant decrease in damages and ant sting incidents, he found.

Currently, the Hawai`i Ant Lab, based in Hilo and funded by the U.S. Forest Service, the Department of Land and Natural Resources, and the Department of Agriculture, has an annual budget of only $200,000 to $250,000, Vanderwoude says, and with that he and his staff are supposed to address all invasive ant problems throughout the state. His staff – just 3.6 people – conducts research on better ways to control the LFA and coordinates with the Hawai`i Department of Agriculture and island invasive species committees to control incipient infestations and educate the public.

A couple of recent community workshops on the LFA were “frighteningly well-attended,” he says, adding, “The demand for residential workshops has been really, really high.”

The ants have already spread to an estimated 6,000 sites from lower Puna to Laupahoehoe on the east side, and to the Kona airport and Ka`u on the west. Some 4,000 homes, 186 farms, six parks, a school, a hotel, and 568 other sites on the island have been infested, Motoki said. Fellow presenter Lissa Strohecker, an outreach specialist with the Maui Invasive Species Committee, added that the Hawai`i island office of the state Department of Agriculture now gets 25 to 30 calls a week from people seeking advice on how to get rid of the pests.

And the ants aren’t just biting people, they’re hampering inter-island trade and tourism.

Motoki reports that the model predict 23 percent of plant nurseries on Hawai`i island are infested with the ant. As a result, a number of landscapers on Maui have stopped importing plants from Hawai`i and have started sourcing locally, according to biologist and environmental consultant Forest Starr.

Visitors to a few badly infested beach parks and the Panaewa Zoo are “constantly being stung by ants falling from trees,” according to the ant lab’s website.

Despite the ant’s obvious impacts, Strohecker said, there still seems to be a lack of awareness on Hawai`i of how bad the pest can be once it’s established.

“[E]ven though properties have ants, residents are often not treating, or treating too inconsistently to be effective, citing treatment cost and neighboring lot access as limitations,” her abstract states.

Government agencies have been encouraging the landscape industry to treat plants, working with farmers markets to encourage testing, and trying to spread the word at community events with the Big Island Invasive Species Committee, among other things, Strochecker said.

Should resource managers ever get an influx of funds to control the ant, Motoki’s model suggests that focusing on suppression in the agricultural, nursery, and lodging sectors would likely yield more economic benefits than focusing on residential, school, and park sectors. However, that strategy would protect far fewer people from getting stung.

Incipient Infestations

So far, the ants haven’t been detected on O`ahu. On a farm in west Maui, a small infestation found in 2009 was thought to be nearly eradicated a couple of years ago, but scientists discovered a nest on the property this year. On a 12-acre site on the North Shore of Kaua`i, after repeated treatment with pesticides, resource managers are now close to stamping out a decade-old infestation there.

To prevent plants shipped from Hawai`i island from causing further infestations, the HDOA requires all potted plants from there to be inspected. If any ants are found, the plants must be treated with pesticide before being shipped. Nurseries inspected twice a year by the HDOA and certified to be ant-free, however, may ship plants freely.

Some scientists and resource managers have recommended tightening the state’s regulations to prevent the transport of any plants from known high-risk areas, but so far, no rule amendments have been proposed.

Presenter Gary Morton of the Department of Agriculture, Fisheries and Forestry in Queensland, Australia, described the protocols and methods his agency has implemented to prevent the spread of the LFA, which was first discovered there in 2006.

In Queensland, where eradication is still possible, 50-meter buffers are imposed around infested areas and landowners are prohibited from moving materials or ants out of the quarantine area without the approval of an inspector, Morton said.

With two trained ant-sniffing dogs (plus their handler), a field staff of five, and strict protocols on moving vegetation, Morton has managed to inspect and treat some 260 hectares.

When inspecting green waste, “that’s where the dogs come in really handy,” Morton said. “They can check some soil and run across some plants very quickly, in a five or ten minute period.”

Morton also advocates for proactively searching for the ants.

“Catching that cycle early, that’s how we’re going to eradicate. There’s less plants that are being moved. Hopefully [we’re] reducing the chance of spreading. … We’re on target for eradication,” he said.

Although penalties for violating the quarantine are high, “we’ve issued warnings but never prosecuted anybody,” he continued, adding that it’s difficult to prove a person knowingly moved infested materials.

Once an infestation is treated with pesticide, his team resurveys the area nine months later with the dogs, then again nine months after that.

“If we find nothing, we declare freedom,” he said.

So how important are the dogs?

For Morton, it means doing only two follow-up surveys rather than three. “They’re also an enormous engagement tool. We’ll do demonstrations at events. They’re such a visible part of our program,” he said.

They are, however, very expensive. His dogs are trained to detect little fire ants – or as they call them in Queensland, “electric ants” – as well as red imported fire ants. The cost of that training: $60,000.

Vanderwoude, who mediated the conference panel on LFA, says the dogs are really handy when eradication is the goal and “where you have to find every last ant.” And they’re also good in a quarantine context. “If you had a trailer load of potted plants … if there was one fire ant in there, they would find it,” he says.

But because they’re so expensive to train and maintain, dogs are not ideal for controlling ants on Hawai`i island, “where we have ants everywhere. … You’re not looking to find an ant,” he says. “There is a use for detector dogs, but it’s important to do the math first.”

More information on this problem as well as how to manage Little Fire Ants can be found on the Hawai‘i Ant Lab


Can the Mongoose
Be Eradicated from Kaua`i?

“Thank you, Theresa. That was very depressing,” said Advancing Biodiversity session moderator Josh Atwood of Theresa Menard’s presentation on how difficult it will likely be to eradicate mongoose from Kaua`i, especially with only a year’s worth of funding in place for a single dedicated technician.

If they can’t be eradicated, the “eggs and hatchlings of ground nesting birds like our state bird, the nene, and endangered sea turtles like the hawksbill sea turtle are especially at risk,” states the website for the Kaua`i Invasive Species Committee (KISC).

No one knows whether mongooses have established a breeding population on the island or if there’s only an incipient one. One mongoose was found in 1968. Another, a lactating female, in 1976, Menard said. They had been sighted sporadically throughout the decades, then in 2012, they seemed to be everywhere. A male was captured near the airport, then a female near Nawiliwili harbor. And there were dozens of sightings.

Menard, a map maker and data analyst for The Nature Conservancy of Hawai`i, KISC’s Keren Gundersen, and John Chapman of the National Tropical Botanical Garden ran various scenarios on a population model to determine what, if anything, could be done to rid the island of the pest that has already established itself on O`ahu, Moloka`i, Maui, and Hawai`i island.

Based on the number of credible, non-overlapping sightings in 2012, the team estimated that there are about 54 mongooses on Kaua`i. Because of the model’s limitations, they set a carrying capacity of 5,000 animals, but the actual capacity could be much higher, Menard said.

Simply put, without consistently high levels of harvest, there’s no chance of eradication. Menard reported that if no more mongooses make their way to the island, and if managers are able to cull 29 of them a year, there is a 50 percent chance that Kaua`i would be mongoose-free after 15 years.

Under a scenario in which only half of the adult females breed, a harvest of 29 a year would eliminate the population in three years. If only eight a year were caught, it’s likely they could be eradicated after 27 years, the model showed.

However, if only two mongooses a year somehow make it to Kaua`i and no more than 29 a year are caught, eradication becomes impossible, the model showed.

To prevent newcomers from supplementing the current mongoose population on the island, Menard recommended signage and inspections.

Trapping the animals has proven difficult. After two were captured in the summer of 2012, staff with KISC, the Department of Land and Natural Resources’ Division of Forestry and Wildlife, the U.S. Fish and Wildlife Service, and Young Brothers spent more than 2,500 hours over the rest of the year setting and checking more than 300 traps. By the end of the year, they had caught mice, chickens, cats, and toads, but no mongooses. No mongoose has been caught so far this year.


Two Candidates for
Miconia Biocontrol

Enemies of one of the worst invasive plants in the Pacific are a step closer to being deployed in Hawai`i. At the conservation conference, U.S. Forest Service entomologist Kenneth Puliafico reported on his progress with determining if two insects from the home range of Miconia calvescens will leave important Hawai`i flora alone.

So far, the news is good.

“In Costa Rica, miconia is a happy little plant,” Puliafico said as he showed a picture of a shoulder-high, lone miconia plant growing alongside a stream there. Outside of its range – in Tahiti, in particular – the plant bosses nearly every other plant out of the forest. In infested areas in Hawai`i, miconia is often the tallest tree around and forms dense stands. Its massive leaves, which can easily grow to be several feet in length, shade out native understory.

With seeds like grains of sand packed into tiny berries, a single tree can produce millions of seeds a year. Because the seeds are widely dispersed by birds and stay viable in the soil for up to eight years, detecting and eradicating incipient populations is labor intensive and costly.

On all of the large main Hawaiian islands – Kaua`i, O`ahu, Maui, and Hawai`i –island invasive species committees have been fighting for years to limit the plants’ spread. Some islands have fared better than others. O`ahu, for example, has all but eradicated the plant. On Hawai`i island, however, the plants have established a stronghold in the Hilo area and are creeping their way along the Hamakua coast. A couple of isolated populations have also been found on the island’s west side.

With limited funds and staff to control the plants, many see biocontrol as the best long-term management option.

At a lab in Costa Rica, Puliafico has been feeding a variety of plants to two insects known to hamper miconia’s reproductivity and ability to shade out other plants. He wants to see what they will eat, what they like the best, and what they’d rather die than eat.

First, there’s the seed-feeding weevil, Anthonomus monostigma, collected from four different miconia species. Adult weevils feed on the fruit; the larvae eat the seeds, he said.

His tests so far suggest that the weevils have very strong preferences for their host plants. However, Puliafico said, he is still working on a list of native Hawaiian plants to test the weevil on.

“The good news is that the Miconia nervosa, invasive in Australia and potentially coming here, has a weevil that loves its host plant. We’ve got an ace in the hole,” he said.

The second insect he’s testing is Euselasia chrysippe, a defoliating caterpillar, which he said have “fun, little larvae that eat all together,” forming great chains along the edges of leaves.

The caterpillars are found only on miconia species and were identified a decade ago as a potential biocontrol agent. Puliafico said he had tested them on 34 species of plants in petri dishes. Fortunately, he said, none of them damaged any native Hawaiian species.

He said he plans to test the caterpillars on even more local plants “to make sure our native species are well protected, and important crop trees.”

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