Repelling ants takes full effort

The general public has a key role to play in keeping little fire ants from taking hold on Oahu. While the Department of Agriculture is confident that the largest known colony can be eradicated, there likely are smaller nests around the island. The ag department lacks the resources to find these colonies on its own, and depends on homeowners to test their properties for the fearsome pests and report any sightings.

So far, the major infestation on Oahu is limited to four acres of land in Waimanalo, which will be cordoned off and treated with a gel bait effective against the stinging ants, which are dwelling by the billions there. Most of the land is vacant and controlled by the state, easing eradication efforts, which also may include removing infested trees.

The tiny, pale orange insects, which are originally from South America, are considered among the world’s worst invasive species. They are a threat to agricultural operations, tourist attractions and Oahu’s general quality of life. Over time, they build up large, interconnected colonies that can overrun a property. They’ve been present on Hawaii island since at least 1999, and have gotten so bad in some parts of that island that farmworkers abandoned infested orchards.

The ants’ arrival on the Big Island predates the extermination technique that has worked on Maui and which state officials expect to work on Oahu, namely the application of a gel bait that can be sprayed into trees where the ants live. The sticky gel, which combines the pesticide s-methoprene with smooth peanut butter and other ingredients, is more effective that earlier dry granules that did not adhere to branches.

The insecticide inhibits the ants’ reproduction, so it works over time and must be reapplied about once a month. It will take many months to kill the ants in Waimanalo, and then three years of monitoring to ensure that they don’t re-emerge.

The intensity of this effort will tax the understaffed ag department, which lost funding several years ago for a full-time survey entomologist, whose sole role would have been to ferret out invasive species at parks, farms and residences. Additional funding to boost agriculture department staffing in this regard is warranted, although of course this effort is a group one that rightly also involves other state and county agencies. Given the rising pestilence and limited government resources, the participation of private citizens, too, will be crucial.

The DOA is asking Oahu residents who suspect their properties are infested to take part in a simple survey (see box). The results could help the department track the remnants of a shipment of hapuu from Hawaii island that generated an ant alert last year. Little fire ants in that crop of Hawaiian tree ferns were detected in a few Oahu nurseries and garden shops in December and quickly dispatched, but only about half the shipment is accounted for, said Robert Curtiss, the DOA’s acting plant control branch manager.

"If someone bought infested material and brought it home, we need to know that," he said. "It’s not certain that all 100 percent of that shipment was infested, but it is likely that more was infested than we have accounted for. We do think that there are others. Unless we are lucky enough to find them or get a report from the public, we don’t have a way to verify that."

So although the worst infestation is being dealt with, Oahu is not in the clear. It will take an enthusiastic community response to keep the island from being stung.