[Ant Control Issue] The little ant that could

I don’t know if you can identify this without seeing it," Scott asked me over my cell phone, "but I am just so curious about what it is!"

"Well, I can give it a try," I said. It seems that the most difficult identifications always come when I am out of the office.

"Let me tell you what I think it is first," Scott said. His first thought was a Pharaoh ant. "Do they have swarmers?" he asked.

"Yeah, but you normally don’t see them because they don’t have a mating flight," I said.
"OK, my next guess was a citronella ant. This ant is yellow in color and about half an inch, and the color tells me it isn’t a carpenter ant or pavement ant."

"Well, that sounds good to me," I said. "Can I take a look at it tomorrow when I’m in the office?"

"Sure. It’s actually Kimberly’s sample, but I am just dying to know what it is, so please let me know, too."

This is the sort of experience that seems to be common in pest management. I can’t remember how often I’ve had ant samples, especially of swarmers or winged ants, brought in for identification. At times, even I could not identify them.

One particular ant that I’ve had to learn to identify since I moved to the Midwest is the pavement ant. This common pest is found in the Atlantic, Midwest and West Coast areas, and only occasionally in the South. Let’s look more closely at this important pest ant.

IDENTIFICATION. I’ve always felt that identification of pests is something that cannot really be taught, but rather, each of us has to find the way that works best for us. Pavement ants are no exception to this. The workers are about 1/8 to 1/6 of an inch in size. Identification guides often report them as being blackish brown in color, although I’ve seen colonies that were more reddish brown and colonies that were more black.

Pavement ants have two segments (or nodes) between their thorax and abdomen. In Wisconsin, this is a good way to distinguish them from other ants, as we have only one other common ant with two nodes, the Pharaoh ant.

Most literature says pavement ants are easily identified by the presence of lines or ridges on their heads and a spine on the back of their thoraxes. Although these features can help identify pavement ants, the feature I use most often is the size of their heads. Most ants have a head that is smaller than their abdomen. Pavement ants have a head that is similar in size to their abdomen. They look like bulldogs because of the size of their heads.

LIFE HISTORY. As their name implies, pavement ants are commonly found nesting underneath pavement. They also can be found underneath other hard objects, such as rocks, concrete and so on. To no surprise, this is also one of the reasons why they become pests indoors, since they will form a nest under the concrete slab of a structure, and then begin foraging inside for food and water.

Because of their habit of forming nests under slabs, they can cause problems year-round, even in states like Wisconsin. This often comes as a surprise to people in colder climates, who are accustomed to most pests dying off in winter.

Unlike so many major pest ants, such as Argentine and Pharaoh ants, pavement ants have only one queen per colony. The colonies have about 10,000 to 30,000 ants.

They can forage up to 30 feet away from their nest site, searching for greasy foods — proteins and fats — or sweets. I’ve often found them attacking bait in rodent stations. Like other ants, they will vary their diet based upon the nutritional needs of the colony, depending on the weather, season and immediate environment.

Mature nests will produce swarmers. These tend to be seen in the springtime, especially after a rain or when humidity levels are high. Pavement ant swarms are hard to forget, since they can be difficult to control and can sometimes come out in huge numbers. Joanna, a technician at our company, told me about a customer whose home she serviced that had an extremely large swarm. The client had gone shopping, and when she returned home two hours later, found her living room was 2 inches deep in swarmers!

INTEGRATED PEST MANAGEMENT. The key to pavement ant Integrated Pest Management (IPM) is prevention. Identify accounts where pavement ants tend to be an annual problem. In the late winter and early spring, before pavement ants begin showing up, apply either a non-repellent liquid treatment, a bait station or a granular bait. In my experience, in many situations, this will stop pavement ant problems before they start.

But, what do you do if pavement ants are still a problem in an account? Or if you have an account where you cannot perform a preventive treatment, such as a food plant? Or if a new customer calls in with pavement ants?

When you have an account with pavement ants despite your preventive treatments, you often have a challenge on your hands. The first step would be to retreat the area with a different bait than you used before, either a bait station, a granular bait or a gel bait. As with any time you are baiting an active infestation of ants, make sure that you have more than enough bait placements, so the ants don’t run out of bait. If that doesn’t provide control, then you will need to find out how they are entering your account and where the nest is located. This will determine your next course of treatment.

When you inspect the outside of the structure, if you find that the ants are entering the building through cracks, the best treatment is to seal the openings and apply a granular bait outside. This will deny the ants access to the building and provide a food source to replace what they are foraging on inside, so they are less likely to seek alternative entry points. You may also want to consider an interior treatment where the ants are being seen. A pyrethroid would be your treatment of choice. Not only would this control the ants that are trapped inside, but should foragers find an alternative entry point, the repellency may help push them outside and into the granular bait you applied.

I had a food plant where the ants were actively foraging through cracks in the slab floor. I couldn’t treat the floor cracks because the slab was covered with a layer of flooring. This flooring had been damaged, and the ants were coming in through the damage. I repeatedly baited the area beneath the flooring with three different baits. The ants would stop foraging for a short time, but never completely went away. Finally, I inspected the outside and found a huge number of ants entering through damage to the juncture where the walls met the slab. One application of a granular bait and some caulking eliminated the problem in less than a week. Because the facility handled food products, I didn’t treat the interior with a repellent. Finding
an entry point on the exterior is often not possible, since these ants often colonize beneath slab foundations. Joanna, the technician I previously mentioned, had another situation where foraging ants were found inside, despite pre-season baiting. We found where they were entering the building and treated the crack with a small amount of a liquid treatment. To our surprise, the treatment quickly disappeared down the small crack. The crack opened up into a large void area, where we assumed the colony was located. We put about half a gallon of treatment down the crack, and the problem ended. Had this not worked, I would have injected a foam with a non-repellent down the crack to better fill the area.

Another option for difficult pavement ants is a sub-slab treatment with a non-repellent insecticide. Some have reported success with this treatment, but make sure your product is labeled for this treatment.

In situations where you haven’t been performing preventive pavement ant control, such as a new account, or an account that had pavement ants show up in an area where you didn’t do a preventive treatment, you have many options for control, depending on your preference and the account.

I’ve found that pavement ants respond very well to many bait stations, granular baits and gel baits. The amount of bait needed depends upon the size of the colony, the active ingredient in the bait, and the acceptance of the bait.

Liquid treatments tend to give good control as well. Generally, either pyrethroids or non-repellents provide excellent results. In most situations, treating areas where the ants show up will do.

CONCLUSION. So what were those ants that Scott and Kimberly called me about that I mentioned a few pages ago? The color made them look like citronella ants, also known as large yellow ants, although they had two nodes, whereas citronella ants have only one node. I found the spine on their thorax and the ridges on their heads, and knew they had to be pavement ants. But what about the color? The ants were found stuck inside a light fixture, so they had been bleached out by the light. The customer didn’t have any other ants to show us because the cleaning staff had cleaned them up.

The author is the training and technical services manager at Batzner Pest Management, New Berlin, Wis. He can be reached via e-mail at tsnyder@giemedia.com.