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Homeowners Left Vulnerable to Leafcutter Ant Excavations

- by Robert Burns, (903) 834-6191, rd-burns@tamu.edu

And you thought fire ants were bad. Fireants are cruel pests, but at least they can be controlled and don't pose a risk to your home.

Leafcutter ants, however, can be a huge pain when it comes to your house's landscape and foundation.

Worse, as older pesticides licensing by the EPA expire, the products can no longer be sold. Homeowners are left without any effective means of controlling the pest, said Dr. Michael Merchant, urban entomologist with Texas Cooperative Extension.

Merchant said that though the leafcutter ant has yet to become a widespread problem in the Dallas metroplex area, it has been a problem for homeowners in east, south and central Texas.

"Their large colony sizes, impressive soil excavating power and destructive potential against plants makes them a serious pest," said Merchant, who is based at the Texas A&M University System Agricultural Research and Extension Center in Dallas.

Not only do leafcutter ants strip landscape foliage of leaves, they create huge underground storage vaults for the leaves they gather. They don't actually eat the leaves, but use them in a form of ant agriculture, inoculating the leaves with a fungus. The fungus eats the leaves; the ants eat the fungus.

Though vegetarian ants may sound charming, in the process of excavating, they can cause both sunken areas in lawns and create large unsightly mounds. On many occasions, they have reportedly tunneled under house slabs and cause them to crack, Merchant said.

Control of leafcutter ants used to be fairly straight-forward with a bait product called Volcano, Merchant said.

But in the U.S., leafcutter ants are only found in parts of Texas and Louisiana. With a limited market area and facing millions of dollars to get the product periodically re-labeled by the EPA, the pesticide manufacturer stopped production.

Other products in this "limited use" category had the same fate.

"Volcano contained the active ingredient sulfluramid, used citrus pulp as the bait, and was very effective," Merchant said. "At the present time there is no equivalent replacement. This may change with time, but currently treatment options are limited."

Two other products are specifically labeled for leafcutter ant control, he said. Grant's Total Ant Killer and Amdro Ant Block are two baits similar to the old Amdro Green Label leafcutter ant bait.

"According to studies conducted by the Texas Forest Service, this type of bait is effective at eliminating colonies approximately 30 percent of the time. If control is not obtained from an initial application, it may be necessary to repeat; but this is no guarantee of control," Merchant said.

The remaining option is to use an insecticide dust labeled for ant control. The product should be applied to all the entrances in the mounds. The products include Orthene, Bayer Advanced Lawn Fire Ant Control Dust, Terro Ant Dust, Ortho Ant B Gone Dust and Spectracide Fire Ant Killer. Multiple applications might be necessary for control, he said.

Fire ant bait controls are not effective on leafcutter ants, Merchant said.

If the mound is on a neighbor's property, homeowners can protect their landscape plants by spraying their foliage with an insecticide labeled for long-lasting control of chewing insects, such as permethrin. This treatment will not eliminate colonies, but will help protect foliage.

"Leafcutter ants are one of the more frustrating pests facing Texas homeowners," Merchant said.

* Article originally from http://agnews.tamu.edu/dailynews/stories/ENTO/Mar2905a.htm

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