Argentine Ant Case Studies

Argentine ants (Linepithema humile) are, in my experience, the most problematic ant pest species in the Carolinas. (And I know many other areas too!) They may not be up to the level of insanity as the tawny crazy ants (Nylanderia fulva), but they are a close second. Every year, starting in the early spring, these ants come out of their hidey holes, multiply and spread throughout the landscape like a virus. These tiny, brown, six-legged alien invaders proliferate and conquer the urban environment.

We think we’re ready for them. We emerge at the same time, fresh from our state association conferences and training sessions armed with new knowledge and better products ready to go to war. With experience, we begin to find their weaknesses. We find products and application techniques that give us the upper hand. We can stave off infestations and annihilate their populations. We feel like we’re winning. But alas, it’s a never-ending war. Inevitably, I get that phone call from a technician who has been defeated and needs my help.

K. Hathorne

ANTS AT THE LAKE. There are some beautiful lakes in the Carolinas and a large number of problem calls come from residences around these areas. Argentines love moisture and living on a lake sets them up quite nicely. Last summer I visited such an account — a stately home on a nice piece of property located at the end of a peninsula on deep water. Hundreds of feet of shoreline wrapped around three sides of the heavily wooded lot lined with riprap rocks. It was an Argentine ant paradise. (I’m sure it would be paradise for many people as well!)

The property had an invasion of epic proportions. Ants were trailing everywhere. All through the rocks along the shoreline, multiple trails on every tree on the property, and anything on the ground was used as a nest site. I could turn over just about any clump of pine straw or piece of landscaping material, put my hand on the ground and have it immediately covered with hundreds of scurrying ants. I had seen similar videos from people dealing with tawny crazy ants.

While there were many ants crawling around the outside of the house, luckily the inside was relatively free from foraging ants. The service technician had done a great job keeping them out of the house, but he knew it was only a matter of time before they conquered this space as well, and the owners were getting nervous. As how these things usually go, I inquired about the products and techniques being used. I asked if bait was being used on this account, and the technician said yes, but he couldn’t keep them filled fast enough, it wasn’t making much difference, and was costing the branch a lot of money. He pointed to the rocks along the shoreline and said, “Ants are living under all these rocks and look how much shoreline is on this property. The number of stations and bait needed would cost a small fortune.” I could see his point.

We brainstormed and came up with a plan. This included extending the treatment zone further out from the house with an imidacloprid product and moving ant bait stations to the bases of trees near the home. I had him switch from a gel ant bait to a liquid ant bait to help cut down the cost. We explained to the customer that cost would prohibit us from eliminating the ants along the shoreline, but adjusting our treatment could impact the populations close to the house; they were fine with that. Following up a few weeks later I learned what we did worked. There were still lots of ants on the property but they were staying far away from the house and the customer was happy with the results.

K. Hathorne

DISH DUTY. So, just as we were feeling pretty good about our victory, another technician in a different area was having an issue with Argentine ants. After eliminating all other colonies on the property, the little buggers kept showing up inside the customer’s dishwasher. The customer wasn’t seeing any trailing ants inside since the initial treatments, but when she would open up the dishwasher in the morning, the dishes already in there were covered in ants. She would, of course, run the dishwasher, which seemed to fix the problem until a couple of days later, when the ants would show up on the new dirty dishes.

Upon inspection of the home and property, we could not find a single ant anywhere. Nothing in the crawlspace or the plumbing lines going into the dishwasher. Not an ant in sight. We figured the colony must be located in a nearby wall void or under the cabinet bottoms so we thoroughly treated these areas. But it didn’t fix the problem — she would still find ants on the dirty dishes from the night before in the dishwasher. I thought, OK there’s no way ants can get into the dishwasher without crossing over a treated area. They’ve got to be inside the dishwasher.

With the customer’s permission, we proceeded to take apart the dishwasher and wouldn’t you know it, there they were all nestled up in the front control panel. They never had to leave because they were being given food and water via the dirty dishes. We took the control panel outside, swept out the ants and then reassembled the dishwasher. They thought they had outsmarted us. But not this time. (Although my head did hurt from banging it against the wall trying to figure this one out. They nearly drove me crazy.)

The author is technical director at Terminix Service, Columbia, S.C.

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