Perimeter Treatment Vs. Baiting

Which is better — perimeter treatment or baiting to prevent ants from entering structures from the outside? One school of thought holds that spraying a 6- to 10-foot band around a structure according to the label can intercept ant foragers before they reach the building. The contradictory opinion is that this treatment gives only temporary relief because a satellite colony inside the structure can mature on its own when cut off from the parent colony.

According to Stoy Hedges, author of the PCT Field Guide for the Management of Structure-Infesting Ants, it depends on the species and which spray is used. He cites work done by Dr. Hanif Gulmahamad in California that shows situations in structures with Argentine ants are sometimes worsened with perimeter treatments using pyrethroid sprays. An article in the May 1999 issue of PCT magazine — "Careful Baiting Halts Infestation of Pharaoh Ants" — cites a study that found outside baits were effective in eliminating a Pharaoh ant infestation. Hedges states that when dealing with Argentine, crazy, white-footed or odorous house ants, regular, complete perimeter treatments are not recommended. He emphasizes that if an effort is not made to find and eliminate the ant colonies, a perimeter treatment will provide only temporary relief.

Finding the ant colony is not always easy, particularly with multi-queen species. With competitive pressures, PCOs cannot afford to spend time locating trails after dark.

In addition, I find most PCOs don’t usually treat a 6- to 10-foot band around a structure; nor do they use the more expensive microencapsulated formulations. The result is a short-lived residual that permits ample time for insect activity between monthly visits. While theoretically ants should be prevented from entering buildings protected with a chemical barrier, I believe it’s a Myth Conception that such barriers are always effective.

STOPPING ANT SPILLOVER. In an effort to test the theory that baiting outdoors can prevent ant populations from spilling over into structures, I am trying to control white-footed ant infestations in our gated community in Deerfield Beach, Fla. The white-footed ant is, I believe, one of the worst possible multi-queen species to test. Their huge colonies seem to produce young faster than we can kill them. It is no wonder that most PCOs in our area will not guarantee control of white-footed ants as they do with other species.

In my four-story building with 56 apartments, white-footed ants are spreading. Behind one particular apartment on the second floor, a scale-infested schefflera tree was supplying endless trails of these ants into our building. A modified Helland liquid rodent bait station filled with J.T. Eaton’s Dr. Moss Liquid Ant Bait was placed near the tree and was promptly visited by the ants. Not until the tree was severely trimmed, however, did the ants cease to trail. A satellite colony in a bedroom fed on the bait for two weeks until it stopped trailing. Another satellite colony on the terrace, however, persisted, took on a life of its own and continued to feed daily on the liquid bait. It should be noted that a small dry bait station nearby was not touched during this dry spell.

Normally, our condo community’s PCOs — Kenny Steinlage and his technicians at Century Maintenance — would dust with a pyrethrin/desiccant to bring immediate relief inside the apartment. In our building, fortunately the resident allowed me to check the bait on the satellite colony nightly. To test the bait for this small colony, I used the 1-ounce Ant Cafe. The liquid bait was well received for three weeks. Just about the time when a dry spell ended here in Florida and driving rains wetted their nest in the corner of the terrace, the ants ceased feeding on the bait. They resumed feeding on the liquid bait when the site dried up. My goal is to persist with the bait to see if attrition wins and eliminates the colony.

FIELD TESTING. A test is in progress in which several condo buildings are receiving only bait for ant control. These ant bait-only buildings will be compared with an equal number of buildings that receive a conventional monthly perimeter spray. It will take several months to get results with the several species of ants that infest our area.

In the meantime, with the other species of ants that PCOs face elsewhere in the United States, I hope that placement of larger capacity bait stations at strategic sites can destroy outdoor populations before they spill over into structures.

On the golf course nearby, I’ve already found that no new mounds of fire ants developed after two months when they ceased feeding on the two 8-ounce Helland bait stations on each side of the mound. It is a Myth Conception that a limited bait supply will control large ant colonies, especially multi-queen species. With smaller colonies, less bait may be needed. Too much bait for small colonies may be wasteful. I believe that the uneaten bait becomes less attractive as it ages and hardens. Bait is especially prone to hardening in hot weather when vapor pressure can help moisture escape through small entrance holes. With the fickle appetite of ants, there is no assurance that any one bait will always be accepted. Humans aren’t satisfied with only one item on a restaurant’s menu. Why should ants be any different?

Katz may be contacted at 954/427-9716.