UH, HDOA Offer Tips on How to Identify, Control Little Fire Ants

Little fire ant

The Hawai‘i Department of Agriculture and faculty and staff at the University of Hawai‘i have recently shared tips to identify and control little fire ants, one of the most invasive and damaging pests in the world.

Little fire ants were found on Kaua‘i and on the Big Island 15 years ago, then on Maui and more recently, about six months ago, on O‘ahu.

“I’ve seen just how devastating the little fire ant can be, and my concern has only grown. I’m now convinced that without an extraordinary effort, the little fire ant will be a catastrophe for Hawai‘i,” Maui Invasive Species Committee manager Teya Penniman says in the movie Invasion — Little Fire Ants in Hawai‘i, produced by MISC (watch the movie at the end of this article).

The little fire ant is much smaller than the tropical fire ant.

The little fire ant, Wasmannia auropunctata, is a serious pest because this tiny ant can easily spread undetected into yards and homes, parks, landscapes, vacant properties and forests.

The ants deliver a very painful sting, similar to an electric shock, to people, pets, livestock and even marine wildlife such as sea turtles and ground-nesting birds. Little fire ants are attracted to eye fluids and typically sting near animals’ eyes, which can lead to blindness due to clouding of the cornea, or keratopathy.

“When you look in the grand scheme of things, the nastiest of the invasive ants with the greatest impact on Hawai‘i is the little fire ant,” Darcy Oishi, branch chief at HDOA Plant Pest Control, says in the movie Invasion.

An area in Kalihiwai, on Kaua‘i’s North Shore, is seen here on a proposed experimental eradication draft document from August 2012.

In 1999, little fire ants were discovered on a property overlooking Kalihiwai Bay, Kaua‘i’s North Shore. Since then, they have spread to a neighboring property, but controlling and eradication efforts have prevented the ants from spreading to other parts of the island.

The first infestation in the state was found in 1999 in Puna, on The Big Island. The ants supposedly arrived at a nursery there on a shipment from a Florida nursery. Though quarantine was placed, ornamental plants had already been sent from the Puna nursery to a private property on Kaua‘i.

Areas on the Big Island infected with LFA as of 2014.

Fifteen years later, the ants are already well established on the Big Island, and have been found but were controlled and Maui. About six months ago, they were found on O‘ahu.

HDOA and faculty and staff at UH Manoa’s College of Tropical Agriculture and Human Resources have some tips on identifying and controlling little fire ants.

Here are the steps for basic detection and control:

STEP 1: WHERE DO THEY LIVE?

— Areas where LFA are commonly found:

• Trees and shrubs, especially any fork at the base of trunk, in crotches of branches, and under moss growing on trees or shrubs
• Flowers, in the stamen and pistil
• Edges of building foundations and concrete slabs
• Cracks in concrete
• Electrical outlets
• Fallen logs and piles of plant debris
• Under potted plants
• Dumpsters, trash cans, rubbish piles
• Stockpiles of seldom-used flower pots, lumber, hollow tiles, rocks etc.

(Modified from C. Vanderwoude, 2008,“General Emergency Response Plan for Invasive Ant Incursions in the Pacific” http://itp.lucidcentral.org/id/ant/pia/Links.html)

STEP 2: ARE THEY PRESENT?

— Use peanut butter as an attractant for detection. Check for ants by smearing a thin layer of peanut butter on one end of a chopstick or any wooden or plastic stake. Place stake on the ground every 10–12 paces, including in potted plants and at the base and in branch crotches of trees. The best times are in the morning or on overcast days, avoiding heavy rain or mid-day sun and heat. After about 40 to 45 minutes, check for LFA on the stake (Watch a video at the end of this posting on how to test for little fire ants).

• Are the ants red-orange, slow moving, and less than 1/16” long (thickness of a penny)?
• If YES, they are probably LFA. Place the chopstick with ants into a zip-top bag and place it in the freezer for at least 24 hours to kill the ants.
• If NO, repeat monitoring with peanut butter every month.

— Identify and verify that they are little fire ants in order to use appropriate control measures.

• On Kaua‘i, call the Kaua‘i Invasive Species Committee at 821-1490
• On O‘ahu, bring bagged ant samples to Hawai‘i Department of Agriculture, Plant Pest Control Branch, 1428 South King Street, Honolulu, HI 96814
• On the Big Island, bring bagged ant samples to UH-CTAHR Komohana Research and Extension Center, 875 Komohana St. Hilo, HI; or Hawai‘i Department of Agriculture, 16 East Lanikaula St., Hilo, HI.

STEP 3: HOW TO YOU GET RID OF THEM?

— Treat with ant bait insecticide. Ant food bait mixed with a slow-acting insecticide is the only effective way to kill and eliminate an LFA colony, because it allows the worker ants to carry the poison to the queen(s).

WHAT TO USE: Only use bait insecticides that are specifically labelled for indoor and/or outdoor use by broadcast application or in bait stations, or in self-contained bait stations for indoor (see LITTLE FIRE ANT PRODUCTS AVAILABLE FOR HOMEOWNER USE for a list of baits that are attractive to LFA, available at Komohana Research & Extension Center).

• INDOOR PRODUCTS:

Extinguish Plus (also for outdoors); Hot Shot MaxAttrax Ant Bait; Maxforce Complete (also for outdoors); Raid Ant Bait III; Raid Double Control Ant Baits II (for potted plants); and Tango (also for outdoors) (bait must be formulated – see www.littlefireants.com/Tango%20package.pdf)

• OUTDOOR PRODUCTS

Advance; Advion Fire Ant Bait; Amdro Ant Block; Amdro Fire Ant Bait; Amdro FireStrike Yard Treatment; Distance Fire Ant Bait; Esteem Ant Bait (fruits, nuts, vegetables); Extinguish Plus (also for outdoors); Maxforce Complete (also for outdoors); Siesta Insecticide Fire Ant Bait; and Tango (also for indoors) (bait must be formulated – see www.littlefireants.com/Tango%20package.pdf)

Read and follow all label directions – some products can be used near food crops (fruit trees, vegetable gardens, etc.), while others cannot. “Rotate” or use different bait products to avoid “shyness,” when ants stop taking the bait. Some insecticides act as insect growth regulators, which affect the queens’ ability to reproduce and prevent eggs and larvae from maturing – these effects take longer to be noticed.

WHEN TO USE: Ants tend to forage when it’s cool and dry. The active ingredients in ant baits are often deactivated by UV light and humidity (including rain and watering), which make them environmentally friendly but require reapplications every 2-4 weeks. It is best to apply baits early in the morning or at dusk, avoiding rain. Do not water before or after bait applications. Read and follow all label directions for safety.

STEP 4: WHAT DO YOU DO NEXT?

— Check, treat, recheck, repeat. It may take several reapplications of bait over a 6- to 12-month period to kill a little fire ant colony. Recheck with peanut butter regularly and treat with insecticidal bait when necessary. It is critical that infested plants, building materials, trash, etc. be treated on-site and not moved or dumped, which will further spread the ants.

Free publications about little fire ants, including “Little Fire Ant Products Available for Homeowner Use,” are available online at http://www.ctahr.hawaii.edu/haraa/arthropod.asp (click on first publication), or at UH-CTAHR’s Extension Office at 875 Komohana Street in Hilo or by calling (808) 981-5199.

The Hawai‘i Ant Lab, located in the HDOA building at 16 E. Lanikaula Street, Hilo, holds a free “ant management clinic” each month in the HDOA Conference room. Pre-registration is required due to limited space. For information on the next class, call (808) 315-5656.

Additional information is also available online:

www.ctahr.hawaii.edu/haraa/arthropod.asp (Dr. Arnold Hara, CTAHR)

www.littlefireants.com (Dr. Cas Vanderwoude, Hawaii Ant Lab)

http://hdoa.hawaii.gov/pi/main/lfainfo/  (Hawai‘i Department of Agriculture)

Watch the movie Invasion — Little Fire Ants in Hawai‘i, produced by the Maui Invasive Species Committee: