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14th little fire ant infestation is reported on Maui in Waihee Valley

MISC said it is actively treating 5 sites – the Waihee Valley site makes 6

Little fire ants are crawling on a hibiscus plant in an infestation in Waihee Valley detected in late August. Maui Invasive Species Committee photo

A Waihee Valley woman who reported being stung by ants on her neck and under her collar in late August helped an invasive species group identify the 14th detection of the invasive little fire ants on Maui.

Maui Invasive Species Committee said Monday that the woman was working near her fruit trees when she was stung. After MISC was contacted by the resident, a site visit was arranged and the ants were identified as little fire ants under a microscope.

The little fire ant, which has been called one of the 100 worst invasive species globally by the International Union for Conservation of Nature Invasive Species Specialist Group, can leave painful stings and blind animals, MISC said. They can create huge colonies (80 million ants per acre) and can fall from trees creating “ant rain” in the wind.

The ants out compete other insects and already have begun altering lifestyles on Hawaii island, where the infestation was first identified in 1999 and is more widespread, with parents avoiding taking their children hiking, fishing and hunting because of the ants.

“We are still decades ahead” of Hawaii island, said Lissa Fox Strohecker, public relations and education specialist for MISC, on Tuesday. “If we can continue to get reports early, then we can hopefully stay on top of it and keep the problem at bay.”

The day after the ants were identified as wasmannia auropunctata in Waihee Valley, a team from the state Department of Agriculture and MISC conducted surveys in the area, adjacent to the Waihee River. Initial surveys indicated that little fire ants were present on three properties. The infestation is estimated to cover 4 to 5 acres, mostly in overgrown vegetation and away from homes, MISC said.

Little fire ants were detected next to the river, raising concerns that the ants may have moved downstream. However, preliminary riverside surveys below the infestation zone did not detect any ants, MISC said. Strohecker said the little fire ants can move “quite quickly” on the stream, as in a Nahiku infestation, and spread out.

The lush Waihee Valley is prime ground for the little fire ants, whose native habitat is rain forest, said Strohecker. But they are resilient and have been found in Wailea and Kapalua and in Kona on the leeward sides of Maui and Hawaii island.

The source of the infestation is unknown at this time, and there is no known connection between this one and a previously infested site at a farm in Waihee. Based on the size of the new infestation, experts estimate that the little fire ants have been present for five or more years, MISC said.

Strohecker said the sites of the 14 infestations are random and do not offer a migration pattern. The longer term colony establishment of recent discoveries may be a result of Rapid Ohia Death quarantine provisions, which include soil movement limits. This may have cut off transport from Hawaii island.

The colonies tend to be slower growing, she said, though they can spread out fast by riding streams. People start to notice the ants when they begin to fall out of trees on them.

Another source of the infestations could be a yet undetected large population on Maui, she added.

This infestation is the 14th detection of little fire ants on the Valley Isle since 2009 and the second detection this year. The ants were found in April in Happy Valley.

MISC said it is actively treating five sites, and the Waihee Valley site will be the sixth. After undergoing a rigorous treatment regimen, little fire ants are thought to be eliminated from other sites, though MISC continues to survey to ensure they are gone.

Area residents who have encountered stinging ants — particularly those who have been stung on their neck and upper body after working with or under vegetation — are urged to report suspect ants by contacting either the Maui Invasive Species Committee at 573-MISC (6472) or the state Department of Agriculture on Maui at 873-3080 by phone or online at 643PEST.org.

* Lee Imada can be reached at leeimada@mauinews.com.