Eradication of invasive species an investment in the future


Eradication — the complete removal of every last individual in a population — is easiest when the population is detected early. For example, testing for little fire ants is simple and critical to detecting ants before they are widespread. Test annually and every time you bring soil, mulch or suspect material to your yard. MASAKO CORDRAY photo

Life in paradise inevitably means dealing with invasive species in some form. From termites to rats, centipedes to garden weeds, there is an unending onslaught of pests we all deal with. Efforts to control them usually buy a temporary respite; we know and expect these pests will return.

Eradication — removing every last reproducing individual (or seed, in the case of plants) — is the gold standard of invasive species management. In theory, eradication is achievable for any pest species, given enough time and money. In reality, time and money are in short supply. Deciding to eradicate a species is a significant undertaking, typically only possible when the target population level is low and accessible.

Goats once ran rampant on Kahoolawe. Introduced to the island in 1793, a gift to Chief Kahekili of Maui from Capt. George Vancouver of England, these hearty hooved beasts quickly took over, limited only by food availability. They devoured the vegetation on the island, threatening native species and exacerbating erosion. Starting in 1910, a host of assorted land managers, including ranchers, the military and the state government, battled goats on Kahoolawe. Over a period of 80 years goats were hunted aggressively — but always a few remained, too difficult to find. When control would cease, goat populations would explode again.

With the last goat finally removed in 1993, goats were truly eradicated from the island. Those last few goats were the hardest to find, yet tracking down the holdouts was critical to the island’s vegetation recovery. As was the case on Kahoolawe, persistence is often a key ingredient of successful eradication efforts.

Not just large invaders can be eradicated — little fire ants, for example, are eradicable. These minuscule ants have something in common with the goats that once riddled Kahoolawe: Removing the last few is the most challenging yet most important part of the job.

Though it took over 80 years and many failed eradication efforts, the last goats were removed from Kahoolawe in 1993. True eradication is difficult to achieve; the most difficult and most costly goats to remove were the last few. The increased effort to eradicate a species is cost-effective in the long run. Kahoolawe Island Reserve Commission photo

“It’s easy to kill 99 percent of the ants. It’s the last 1 percent that makes it tricky,” says Cas Vanderwoude, manager of the Hawaii Ant Lab. His organization provides the expertise behind the efforts to eradicate little fire ants from Maui. And, as with any attempt to truly eradicate an invasive species, most of the work lies in finding the last few. “Surveys are essential to understanding where the ants are, how effective the treatment is, and if the population is eradicated,” he said. Currently, the Maui Invasive Species Committee and Hawaii Ant Lab anticipate that infested properties will be monitored indefinitely to ensure the little fire ant has been eradicated.

The fact that these tiny invaders also live in trees adds to the challenge. Historically, treatment of the little fire ant relied on granule pesticides developed for fire ants in general. These granules could only be scattered on the ground and did nothing to control the colonies of ants living in trees.

In Hawaii, worker ants find enough food in trees, relying on sap sucking insects and other food sources, never needing to forage on the ground. Without workers carrying bait back to the queen in the nest, the colony will survive, reproduce, and reinvade, as the goats of Kahoolawe did time and time again. Fortunately, the Hawaii Ant Lab has developed techniques for controlling little fire ants on the ground and in the trees.

On Maui there is only a handful of little fire ant populations: Nahiku, Kapalua, Huelo and Waihee. Though eradicating these infestations will be a challenge, complete removal of the little fire ant from Maui is the goal, thanks to the expertise of the Hawaii Ant Lab.

Eradication is time-consuming and expensive, though the price is negligible when compared to the never-ending cost of suppressing these pests so we can continue to enjoy life in Hawaii as we know it. Economists estimate that the cost of damage from little fire ants on Hawaii island will exceed $140 million if current trends continue.

Eradication is costly, but it is an investment in the future. You can help to keep little fire ants at bay by ensuring you do not have any present on your property. Survey your yard for the little fire ant. Quarantine and test potted plants, mulch and soil before distributing it on your property. Find testing information online at or

* Lissa Fox Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. “Kia’i Moku,” “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy and quality of life.