Shipments spreading coqui

By Karen Blakeman
Advertiser Staff Writer

The invasive coqui tree frog, that tiny night singer with a big voice and a two-note repertoire, has been expanding from its foothold in the damper areas of the Big Island to the rest of the state, including O'ahu.

The coqui, named after its distinctive two-note call of "ko-KEE, ko-KEE," has made its way to O'ahu and other Neighbor Islands via plant shipments from the Big Island. The tiny tree frogs are said to threaten to the environment. Associated Press library photo

"This is not the first meeting," Yasunaga said, "and it certainly won't be the last."

Windward and North Shore nurseries on O'ahu are doing their best to control frog populations as they come in, Yasunaga said. But the threat posed by Big Island plant exports could outpace them if more measures are not taken.

"We need to go several steps back," Yasunaga said, "and make sure nurseries on the Big Island get their stock clean before it is sent anywhere."

Inspections are not always effective, said Mindy Wilkinson, invasive species coordinator for DLNR. The frogs are tiny — adults normally grow to about an inch and a half long — and are difficult to see. They are nocturnal and hide in soil and between the leaves of palms and bromeliads during the day, she said.

Yasunaga said inspectors have been exploring various eradication measures for plants that are to be shipped, including exposing the plants to brief bursts of steam heat, but none have yet been perfected.

Meanwhile, the frogs are showing up in areas beyond the infected nurseries.

Recently, he said, the frogs escaped directly from the truck bringing plants to the store, and took up residence in a landscaped area near the parking lot.

State officials responded quickly after his boss called the problem in, and helped Home Depot mix a citric acid potion to kill the frogs, he said. Plans for replacing the vegetation in the landscaped area with an environment less hospitable to frogs — such as a rock garden — are being developed, he said.

"Everybody is real conscious of this," he said, "and we seem to be right on top of it."

Kuebitz said he did not find the call of the coqui offensive.

"It was sort of a deep woods sound," he said. "I thought it was pleasant."

Yasunaga said homeowners with coqui infestations seldom feel the same about the frogs' call.

"They usually call up and say, 'I've got this bird in my yard, and it is keeping me up all night,' " she said.

The call, a loud, two-note whistle, is made by the male of the species, Yasunaga said. He awakens as the sun sets, climbs five to six feet up a plant and repeats his call until a female responds.

On a bad night out, the coqui may repeat his call until the sun rises and it is time again for him to return, silently, to the dark, damp underbrush.

Larry Nakahara, plant pest control manager for the Department of Agriculture, said state officials recommend the methods used by Home Depot to other businesses and homeowners with a coqui problem.

A company is repackaging citric acid, a plant component especially abundant in citrus fruit that is also used in cleaning compounds, in small, easily mixed potions for use by homeowners and businesses in Hawai'i. Earlier experiments with caffeine proved to be too expensive for general use, he said.

Mixed in water and sprayed onto the plants where the frogs are living, citric acid kills coqui in about 45 minutes, he said. Unfortunately, it also burns many plants.

Tropical plants at Puna's Lava Tree State Park on the Big Island are being sprayed to rid them of frogs, then removed and replaced, he said. Native plants are being used as replacements, because they are less hospitable to the frogs.

Changing the habitat is often the only way to control the frogs once they've become established, Nakahara said. Tropical plants with damp, shady areas beneath their leaves are ideal living areas for the coqui. Dead leaves beneath plants also help to keep the soil moist and give the coqui a place to propagate.

Replacing lush tropical plants with drier plants, such as some of the native species, creates an area less likely to attract the frogs.

Homeowners and business owners who notice an infestation in the early stages are probably better off capturing the frogs and disposing of them in a humane manner, he said.

Educational programs on coqui control measures are being aired on Big Island television, he said, and state officials plan to distribute the programs on O'ahu and the other Neighbor Islands.

Yasunaga asked that anyone who suspects a coqui invasion — or the presence of any other sort of invasive species — call the Agriculture Department's pest control hotline at 586-PEST.