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Citric acid treatment plan in the works for invasive coqui frogs found in Waimānalo

Hawaiʻi Invasive Species Council

A population of invasive coqui frogs has nestled in a deep ravine at the base of the Koʻolaus in Waimānalo. The first reports came in February 2021, but officials have had little success in eliminating them altogether.

So for the first time on Oʻahu, officials may have to resort to aerial spraying to beat back the population. The property is conservation land owned by the Board of Water Supply and the departments of Land and Natural Resources, and Hawaiian Home Lands.

State Sen. Chris Lee, who represents the area, says the colony seems like it was there for some time before anyone discovered it.

"But when it was discovered, it was clear that there was a fairly sizable population, certainly with the potential to spread," Lee said. "If it had been there this long without being detected, there really is that critical mass that creates the opportunity for getting into some of the nurseries in the area, and those plants being distributed all around the island. And once we get to a situation like that, there's no turning back."

Lee says there's an inter-departmental plan in the works to spray citric acid treatments to control the area.

"The broader application of citric acid could be an aerial target, where they come in, sort of like putting out a wildfire with a water drop — and that's been shown to be really successful," he said.

Lee says the DLNR, along with the Department of Agriculture and the Oʻahu Invasive Species Council, will be the boots on the ground.

"The department can work with all of us elected officials and our community leaders, neighborhood boards and others to make sure that word gets out there within hours or day's time so that everybody knows what's happening — and to educate on the risks of what this entails, and not doing it entails," Lee said. "And so I think right now, it seems pretty clear that everybody doesn't want coqui to spread."

The frogs are widespread on Hawaiʻi Island where the battle has already been lost.

To eliminate or control invasive species like the coqui frog in the long term, Lee says Hawaiʻi will need to allocate additional resources.

"There was an estimate a few years ago that took a look at what it would cost to contain the spread of invasive species all throughout the islands. And that number was in excess of $50 million a year," he said. "Right now, we're budgeting only a fraction of that for many of our invasive species efforts, including this one."

Local officials rely on the public to report persistent or new invasive species. If you see this species on Maui, Oʻahu, Kauaʻi, Molokaʻi or Lanaʻi, call 643-PEST or visit 643pest.org.

To mark Hawaiʻi Invasive Species Awareness Month, The Conversation will have updates throughout February on the battle against invasive species across this state. This interview aired on The Conversation on Feb. 1, 2022. The Conversation airs weekdays at 11 a.m. on HPR-1.

Catherine Cruz is the host of The Conversation. Originally from Guam, she spent more than 30 years at KITV, covering beats from government to education. Contact her at ccruz@hawaiipublicradio.org.
Sophia McCullough is a digital news producer. Contact her at news@hawaiipublicradio.org.
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