Hi'iaka's Healing Herb Garden

OUCH! Little Fire Ant Is the Latest Invading Insect

Although the little fire ant was first reported in Hawaiian Paradise Park (Puna District) in 1999, it is one of the most serious nuisances to hit our island in recent years. This tiny ant (LFA, or Wasmannia auropunctata) is barely 1/16 inch long, but its sting can be more than a nuisance and has caused blindness in pets when it gets into their food, crawls up their face, and stings them in the eye. Humans are not immune, and those who “might have an anaphylactic allergic reaction could suffer serious harm,” according to a Hawai‘i Department of Agriculture (HDOA) flyer. The flyer also states, “its sting produces large, painful, raised, red welts, which can last several days, aching painfully at first and later itching intensely in spells.”

Where are they?

Over 50 populations are already established in East Hawai‘i and HDOA is currently fighting the first known infestation on Kaua‘i, which began in 2000. Native to Central and South America, the little fire ant likely found its way to a plant nursery here, then it was inadvertently spread. A heavy infestation “can make a property difficult to use commercially or enjoy recreationally,” because the LFA climbs trees and can “rain down in large numbers when you are pruning branches, harvesting fruit, or picking flowers. Some orchard workers in East Hawai‘i have quit their jobs because of this,” according to the HDOA brochure, mentioned below.

How to identify and detect the LFA

Little fire ants are very small and red-orange in color. They move slowly and live in the roots of potted plants and in the soil, as well as in trees and other plants. It’s wise to examine the roots of any purchased plant as soon as you bring it home, before you plant it in your yard. If you find any ants, do NOT transport the affected plants to another location. The Department of Ag asks that if you find any LFA that you report them to their office in order to help control new infestations. (Call them in Hilo at 974-4140.)

Peanut butter is the best lure. Smear a thin layer on a chopstick and place several around your property in the shade. After about one hour, check the sticks to see what you’ve got. If you see tiny red-orange slow-moving ants that easily fall off the chopstick, you’ve most likely got the LFA. Put the sticks in a zip-lock plastic bag, seal it, write your name and phone number on it, and then put it in your freezer overnight. Do NOT transport live ants. Then drop your bag at the Ag Department office in either Captain Cook (next to the police station) or Hilo (16 Lanikaula Street).

Controlling the LFA is tricky

If you determine that you have the LFA, or think you might, contact the Department of Ag, who will advise you how to take care of it. They are fairly easy to suppress in small areas but can be “very difficult to eradicate completely.” If neighbors work together, control is more effective. HDOA requests that you don’t apply any pesticide until after you have contacted them so they can map the occurrence and learn the extent of the infestation. Unfortunately, only chemical pesticides are known to be effective in their control.

Is there any hope?

I asked Tommy Thompson, a researcher on the LFA at University of Hawai‘i, this question and he wrote to me:

“On an individual level, I think there is some hope (at least in the short-term). We already have the tools and knowledge to keep LFA populations down. However, this ability comes at a great cost. The available baits are expensive and it takes time and proper planning (due to the typically wet weather) on the part of the landowner to get the treatments done effectively. Additionally, when treatments are halted, the populations rebound to pre-treatment levels within several weeks. I believe that with enough diligence, time, and money a person could eradicate LFA from a small lot, but most of the time the person’s neighbor(s) is also infested. If you don’t get the same effort from all neighbors in an infested area, reinfestation is imminent.”

He went on to say, “I’m most concerned for the more pristine forests. If LFA reaches a place like Volcanoes National Park (and the surrounding undeveloped area), there would be a great loss of native species (insects, spiders, birds). Research has not yet been done on the temperature tolerance of LFA in Hawai‘i, so we don’t know for sure if it can reproduce at these higher elevations—a small body of evidence suggests that it can. A major part of the problem has been that there is no intra-island quarantine for LFA. It’s my understanding that HDOA will be implementing this, but I don’t know when or how.”

On the Web:

ctahr.hawaii.edu/ctahr2001/PIO/FreePubs/FreePubs06.asp#InsectPests (see “Stop the Little Fire Ant”)
hawaii.gov/hdoa/pi/ppc/test-area/npa-1/npa99-02-lfireant.pdf

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Barbara Fahs is the owner and creator of Hi`iaka's Healing Herb Garden, LLC and author of the book Super Simple Guide to Creating Hawaiian Gardens, which contains information about invasive species. Contact her at 966-6126 or www.hiiakas.com to learn about her workshops, internships and Garden tours.