Tawny Crazy Ants: No Stingers but Pests Nonetheless

(News article for September 14, 2024; edited)

A client recently contacted me about ants on his property. They turned out to be tawny crazy ants (TCAs; Nylanderia fulva). These invasive ants have been identified from Tangipahoa and Washington Parishes, along with a number of other parishes in southern Louisiana.

The name “crazy ant” comes from their erratic movement. Their foraging trails are wide, approximately 4 inches or more. Individual worker ants are reddish-brown and about one-eighth inch long. Their colonies grow to contain very large numbers of ants with multiple queens, and people often find piles of dead ants. It’s not surprising that my colleagues and I are getting calls about TCAs in late summer, as by this time of year, their populations can be quite large.

Unlike many ants, TCAs do not build mounds, and colonies do not have one centralized nest. Instead, colonies have multiple nesting sites in locations that are humid but protected from rainfall. Plant pots, wood, stumps, rocks, leaf litter, and many other materials can harbor TCA nests. One way they cause problems is by nesting around electrical equipment.

Unlike fire ants, TCAs do not sting, and their bite typically does not cause significant pain for humans. However, their copious numbers make them a serious nuisance. They can harm birds and other small animals, and reports from elsewhere suggest that they can harm some livestock.

Once tawny crazy ants are present, more than one tactic will be needed to manage them. Diligence is important.

First, remove clutter and debris under which TCAs could nest. Make sure that trees, shrubs, and other vegetation are not touching buildings. As recommended for preventing many types of insects from becoming indoor pests, try to eliminate openings through which insects could otherwise enter houses and other buildings. Avoid accidentally moving TCAs to other locations with plants, hay, garbage, or other materials or equipment.

Managing insect pests of trees and shrubs that produce honeydew, as discussed in the recent article about sooty mold, can be helpful, since TCAs feed on honeydew, among other things.

We often recommend baits as part of managing fire ants. While baits can be a component of TCA management outdoors, few products have proven attractive to them. Also, TCAs cannot be relied on to keep being attracted to the same type of bait. (For a bait to work, not only does the insecticide in the bait need to be effective against the insect, but the attractant needs to appeal to the insect.) Two bait products recommended for TCA management are Advance Carpenter Ant Bait (abamectin) and Maxforce Complete Granular Insect Bait (hydramethylnon). Baiting is likely to be more useful in early spring when TCA populations are smaller, or when TCAs have just begun to get established in an area, than when ants are more numerous.

To reduce the chance of TCAs entering houses and other buildings, insecticides labeled for perimeter or crack-and-crevice treatments can be used. A number of these exist. Many contain one of the pyrethroid chemicals (active ingredients ending in “thrin”). Alpine WSG (dinotefuran) and Orthene Turf, Tree & Ornamental products (acephate) are other options. (I’m primarily addressing outdoor treatments. If you plan to use an insecticide indoors, make sure it’s labeled for indoor use.) In parishes from which TCAs have been identified by an LSU AgCenter entomologist, pesticide applicators certified in an appropriate category can apply the insecticide Termidor SC (fipronil) as a perimeter treatment for TCAs, under a Section 18 Emergency Exemption label. (The current Section 18 label expires September 27, 2025.) Tangipahoa and Washington Parishes are both among the parishes in which Termidor SC can be used for TCAs. Instructions on the Section 18 label should be followed when using the product for TCAs. Up to two applications of Temidor SC can be made per year.

Where dead ants accumulate on surfaces that have been treated with an insecticide, remove the ants so that living ants cannot avoid the insecticide by crawling over dead ones. Try to do this in a way, such as by using a leaf blower or vacuum, that doesn’t remove insecticide residues.

There are insecticides containing some of the active ingredients listed above – including acephate, dinotefuran, and pyrethroid chemicals – that are labeled for application to other sites where TCAs might be found, such as in lawns and on and around landscape plants. When nesting sites are found, use an insecticide labeled for the respective site.

Where TCA infestations are severe, a person might consider hiring a certified pesticide applicator to broadcast the granular insecticide Topchoice (fipronil) in turfgrass and landscape beds. One application of Topchoice can be made in a year. Fipronil’s toxicity to fish, aquatic invertebrates, and birds makes it essential to avoid contaminating water bodies, or water that will enter water bodies, when using Topchoice or Termidor SC.

Be sure any insecticide you plan to use is labeled for the site and, if applicable, the type of plant on which you plan to use it, and read and follow label directions.

Let me know if you have questions.

Contact Mary Helen Ferguson.

Reference to commercial or trade names is made for the reader’s convenience and with the understanding that no discrimination or endorsement of a particular product is intended by LSU or the LSU AgCenter. In some cases, other brands may be available.

pile of dead ants along edge of building

When tawny crazy ants are present, people often find piles of dead ants. (Photo: Fudd Graham, Auburn University, Bugwood.org)

10/1/2024 6:06:13 PM
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