May 10, 2013

The hidden costs of fire ants

By Madeline McCurry-Schmidt / ASAS Communications

The head of an imported red fire ant. Photo from April Noble, Antweb.org, Bugwood.org

The head of an imported red fire ant. Photo from April Noble, Antweb.org, Bugwood.org

It starts with a pinch.

A slight pinch from her mandibles is all the warning you’ll get before a fire ant stings. Her venom causes an angry, fluid-filled pustule on the skin. In the worse cases, her sting causes anaphylactic shock, even death.

Across the southern United States, people know to watch out for invasive fire ants in parks and urban backyards. But fire ants also cause unexpected, expensive issues in agricultural areas.

“It’s a health and safety issue in the city. In rural areas, it’s an economic issue,” said Dr. Paul Nester, an Integrated Pest Management Program Specialist with Texas A&M AgriLife Extension.

Nester said that though fire ants harm people and livestock, they also damage farm equipment and facilities.

Like many ants, fire ants are mysteriously drawn to electrical fields. According to Dr. Bart Drees, Professor of Entomology and Extension Specialist at Texas A&M AgriLife Extension, once an ant gets shocked by an electric current, it will attract other ants to the spot. This is especially dangerous in electrical systems, like air conditioners, where a switching mechanism needs to open and close.

“Soon you have a big wad of ants that prevents that switch from operating,” said Drees.

Fire ants also nest in utility boxes and disrupt operation. According to a 2006 study “An Economic Impact of Imported Fire Ants in the United States of America,” fire ants caused nearly $640 million in damage to electrical and communications equipment in 2003.

A imported red fire ant mound. Photo from Jake Farnum, Bugwood.org

A imported red fire ant mound. Photo from Jake Farnum, Bugwood.org

Fire ants can also damage harvesting equipment. They can build mounds up to 28 inches high. When certain cutter bars hit the mounds, the equipment can break. Though this is less common with modern cutters, the mounds can still slow down harvest.

These hidden costs may make you want to grab a jug of insecticide and run to the nearest mound. But Drees said it is important to add up costs when considering a traditional pesticide. He said baiting can reduce the fire ant population by 90 percent, but using a registered granular bait product costs around $10 per acre plus application cost. Esteem (pyriproxyfen), Extinguish (methoprene), AmdroPro (hydramethylnon) and Extinguish Plus (methoprene plus hydramethylnon) are registered for application to range and pasture land. If the producer is not seeing at least $17 per acre in fire ant-related losses per year, Drees said baiting might not be worth it.

Drees said certain common sense steps can reduce fire ants and save producers money. This approach is called Integrated Pest Management (IPM). In the United States, many Extension offices have a related IPM program.

Drees recommended an IPM approach to reduce the spread of fire ants. Fire ants often colonize hay bales. If producers remove bales from fields immediately after baling, they can keep ants from moving in and spreading to new areas when bales are moved.

A common IPM method is to look for species that will naturally control pests. Entomologists have discovered that a species of parasite called phorid flies will attack fire ants. A female phorid fly will lay an egg inside a live fire ant, and the ant will eventually die. This form of “biological control” can reduce the need for pesticides. Several populations of phorid flies have been established in the southern United States.

If fire ants are already nearby, producers should reduce weeds and clear unused lumber from areas near electrical equipment and machinery. Producers should also seal electrical components when possible.

Native southern fire ants. Photo from Whitney Cranshaw, Colorado State University, Bugwood.org

Native southern fire ants. Photo from Whitney Cranshaw, Colorado State University, Bugwood.org

Outside of Texas, people should contact area Extension programs to learn how to deal with local fire ants or visit http://www.eXtension.org/fire+ants. Some fire ant species are actually native to the United States. These native species are not considered pests. Native fire ant species are difficult to identify as different from the imported species and have largely been displaced in areas where these exotic species have invaded.

Nester said people in the Midwest and Northern United States do not need to worry about fire ants. Imported fire ants are originally from South America. Though the ants may spread north in warmer months, they die off during harsh winters.

In some areas, fire ants are a welcome invader. Drees said sugarcane farmers in Louisiana actually like fire ants because the ants eat sugarcane borer larvae. Fire ants also reduce tick populations.

Entomologists doubt that imported fire ants will ever be eradicated in the United States. Fire ants are too good at dominating other species. The red imported fire ant even has a scientific name to match its ferocity: Solenopsis invicta. The word “invicta” is Latin for “unvanquished.”

It looks like those in the southern United States will have to keep watching their feet and dreading the sting.

“It burns like fire,” said Drees.

To learn more about fire ants, visit: http://www.extension.org/fire_ants