Massive spraying targets frogs

By Jennifer Hiller
Advertiser Staff Writer

In an attempt to eradicate the little frog with the chain-saw voice, officials sprayed about 900 gallons of citric acid over foliage and eucalyptus trees as darkness fell last night at Schofield Barracks.

Workers from the state Department of Land and Natural Resources' Division of Forestry and Wildlife were among those involved in the spraying of 900 gallons of a citric acid solution to eradicate coqui frogs at Schofield Barracks last night.

The adult coqui frog is not much bigger than a quarter, but the noise it makes is comparable in decibels to that of a chain saw. Deborah Booker • The Honolulu Advertiser

It was the largest attempt so far to kill the invasive coqui frogs, which arrived in the Islands as hitchhikers on imported landscape plants.

The animals are tiny. An adult is not much larger than a quarter, and eggs are the size of fertilizer pellets. But the nocturnal frogs have a song as loud as a chain saw at 90 to 100 decibels; they keep residents awake with a call that sounds like their names: "ko-KEE."

O'ahu officials are trying to avoid what happened on the Big Island, where coqui frog colonies have multiplied from 3 in 1999 to more than 200 today. Citric acid has been successful in killing the frogs on other islands.

This was the third spraying with large equipment in the East Range of Schofield Barracks, the location of the only wild coqui population on O'ahu. Officials have also gone through with backpack sprayers and flashlights several times to try to spray the frogs on sight, said Christy Martin with the Coordinating Group on Alien Pest Species.

Removal of the frogs by hand worked earlier this year, but eggs left behind hatched and reinfested the area.

Nilton Matayoshi of the state Department of Agriculture's Plant Pest Control Branch said the citric acid solution is about twice the strength of lime juice or lemon juice. The acid may cause brown spots on some of the more delicate plants. But it kills the coqui frogs in a matter of minutes and does little harm to other plants and animals.

In their native Puerto Rico, the frogs are said to be beloved by islanders who enjoy their melody at bedtime, but in Hawai'i the noise has prompted complaints. The piercing call heard at a distance of 18 inches is comparable to the noise produced by a lawn mower, table saw or helicopter.

One woman on Maui was so bothered by the nighttime noise that she called officials in tears asking for help in removing the frog from her tree.

The frogs were first heard in the Islands in 1992 and are found on the Big Island, Maui, O'ahu and Kaua'i. They are so widespread in some areas, covering hundreds of acres, that their removal may be impossible.

The Hilo-side of the Big Island, in particular, has been plagued by an influx. A few months ago, officials on Kaua'i sprayed the L?wa'i Highlands with citric acid to eradicate an infestation there.

The male coqui can start calling at about three months of age; their life span is more than two years.

Officials are worried about the potential for a larger invasion if the problem goes unchecked. In times of good rainfall, the female coqui can lay about 18 eggs at a time every couple of months, said Mindy Wilkinson, invasive species coordinator with the Department of Land and Natural Resources' Division of Forestry and Wildlife.

"It could grow exponentially in a year," she said. "You put it in an environment where nothing really eats it, and it just flourishes."

Even if O'ahu's wild coqui population is wiped out or contained, the island will remain at risk from the infestation from the Big Island.

For now, officials will continue checking with Wahiawa residents and returning to the East Range to check the noise level. They expect to have to spray at least a few more times.

"It depends on how successful it is," said Army entomologist Robin Yamamoto. "You come back, you listen, you hope you don't hear anything."

Reach Jennifer Hiller at jhiller@honoluluadvertiser.com or 525-8084.