Fire ants: Little pest, big problem invading isle


Many have felt the sting of a bee, tropical fire ant or a centipede. However, one thing Kim Johnson hopes West Hawaii residents will avoid is the electrifying pain of a little fire ant.

Johnson has felt this long-lasting burning sensation more than once since discovering six weeks ago the stinging red ant, Wasmania auropunctata, at her 3-acre Left Coast Farm in Honaunau. She showed some scars and burns Tuesday following the Kona Coffee Farmers Association’s Coffee Talk in Kainaliu.

Michelle Montgomery, an invasive ant research technician with the Hilo-based Hawaii Ant Lab, told of the dire implications of this tiny ant; its effects on residents, pets, wildlife and those in the agriculture industry; as well as how to detect and control it.

Native to Central and South America, this barely 1/16-inch-long ant has detrimentally infested areas around the world, particularly tropical and subtropical places in the Pacific. Transported to new sites, usually in potted plant and other materials, including mulch and rubbish, these ants can become a serious nuisance. They will infest house lots, gardens, forests, agricultural fields, beaches or parks. Coffee farmers may see stunted growth, fruit spoilage and premature fruit . It also may be difficult to find pickers and prune.

Then there are the quarantine issues, preventing the shipment of commodities, Montgomery said. “This is something you need to take seriously,” she said. “It can devastate your business.”

Their stings burn strongly and itch intensely for weeks and they pose potential danger through allergic reactions. The stings are also known to harm animals, including livestock, and multiple stings can cause clouded corneas, blindness or death, Montgomery said.

“The little fire ant is considered one of the nastiest ant species because of its biology and cryptic nature,” Montgomery said.

Little fire ants do not compete between their small colonies. Instead, they are interconnected, forming three-dimensional super colonies. The ants share resources, as well as cooperate in taking over areas with shade and moisture. They’re found in plants of all sizes, located high and low, and have a preference for banana plants, ti and palms. Little fire ants will also out-compete other ant species and insects for food and resources, she said.

First noticed in 1999 at a Hawaiian Paradise Park nursery in Puna, the state Department of Agriculture enforced quarantine regulations to halt the pest’s spread.

Little fire ants have spread from the east side to at least eight sites on the west side. The Left Coast Farm detection is the first time the pest was found on coffee land. So far, the highest elevation ants have been found is 2,000 feet, Montgomery said. It is likely there are other unreported infested sites, located higher and in West Hawaii, she added.

Commonly used in fire ant control are baits laced with a slow-acting toxin. Of those available and tested for their effectiveness, Amdro, Probait and Maxforce are the most attractive to little fire ants. However, these baits cannot be used on food crops. Extinguish Pro and Esteem can be used on food crops, but ants aren’t interested in these baits. Other drawbacks are the slow-working, granulated baits can take awhile to work and lose effectiveness with moisture. Also, ants don’t eat solids; they consume liquids, Montgomery said.

Hawaii Ant Lab developed a bait matrix called HAL gel bait, with the active ingredient Tango, a pesticide containing methoprene that regulates insect growth. It prevents insect larvae from completing the pupation process and it also prevents the queen’s egg production. Though not organic, Tango is used for insect control in food crops, produces results in two to three months, and is considered one of the safest insecticides available, Montgomery said.

The gel bait recipe is available at littlefireants.com. Little globs should be sprayed over the ground and infested area every four to six weeks for a year, she added.