Putting Ants in the Crosshairs

An ant is an ant is an ant. At least that’s what most people think, but it’s not true. Just like each person is an individual with certain preferences, habits and quirks, each ant species is the same. Of the 14,000 plus ant species identified thus far, only a relative handful are pests in structures in the U.S. (maybe 70 species); of those, just a few may be considered regular invaders of buildings in any given neighborhood. This means the pest professional servicing homes and businesses in his community can really get to know his key six-legged, colony-forming opponents. Once the habits and behaviors are understood, an ant infestation can be targeted for effective management strategies.

KNOW YOUR TARGET. Identification of the target pest is the basis for effectively managing structural pests. The key for pest professionals is to know how to identify the key pest ant species in their area. A professional in New England will encounter about four types/species on a regular basis while a professional in south Florida may need to be able to identify 10 or more types/species of pest ants. Knowing the types/species of ant causing the problem gives you its preferences on where it likes to locate its nests and its habits that may be important in determining which control strategy you might choose.

Take for example, carpenter ants of which in the U.S. about 25 species may be found invading buildings. In New England, Camponotus pennsylvanicus is the key pest species. Its parent colony is typically found in moist dead wood, usually outside in a stump, tree hole, or landscape timber. A mature colony may have a dozen or so satellite colonies that are usually the colonies found indoors. The Florida carpenter ant, C. floridanus, also nests in tree holes and stumps but also will have satellite colonies located underneath stones, logs, cardboard, and other items lying on the ground. If the Florida professional focuses only on inspecting for colonies outside in dead wood, he likely will be overlooking key satellite colonies located under items.

Let’s say a pest professional in Kentucky finds small brown ants inside. If these are pavements ants, he should focus on finding colonies in the soil along and under the foundation and under stones and other items on the ground. But if they are odorous house ants, the inspection outside should focus on mulch, any stacked items, and leaf litter on the ground, as well as on the roof and in gutters.

SIZE UP THE INFESTATION. My ant control inspection begins the moment I walk onto a property. I look at the landscaping for tree holes, thick ivy on the ground, mulch vs. gravel in the landscape beds, trees/shrubs touching the structure, and plants that might be aphid-prone, thereby serving as a food source for ants. Is leaf litter accumulated under plants or along the foundation? Are mounds of displaced soil present along walkways, cracks in pavement, or in the lawn? I then turn my attention to the structure itself. Do the gutters appear to be in good shape? Any leaves on the roof? Signs of excess moisture in soffits, porch columns, siding, etc.? And this is just for the immediate front of the building.

This degree of surveying is important because you need to be ready to check for other species of ants that might be present. Although my target ants might be carpenter ants, it is possible that odorous house ants or pavement ants also are present near the structure and, if left unchecked, might invade the building later, prompting a call for extra service. I once found nine colonies of seven different species of ants around a home in south Florida, just by pulling the grass away from the foundation to check the space between the soil and the concrete which is used by all kinds of arthropods for harborage.

The next step is the interview with the customer to find out where ants have been seen. If ants are not found in these areas, I’ve found it helpful to pull carpet back from the edge of walls in the area, using needle nose pliers, to check for foraging ants. This allows you to at least find specimens to identify, and if ant trails are present, you can follow the trail back to where it exits under a wall or maybe into a crack in the slab. From there, checking the outside of that wall might reveal a source for the ant invasion indoors.

FIND THE SOURCE. Once the target ant species is known, inspections should focus on where that particular ant prefers to nest. Soil-nesting ants, like pavement and big-headed ants, will involve inspecting along the foundation outside, looking under items and for mounds of displaced soil, and at potted plants if they are big-headed ants.

If inspecting for carpenter ants, the parent colony is almost always going to be outside in moist dead wood unless a water leak has soaked wood indoors (i.e., soffits, window frames, crawlspaces). Indoors, focus on rooms/walls where ants are seen most often. Look for piles of frass under hollow doors or along walls. Listen with a stethoscope to voids under and above windows. Check hollow curtain rods, boxes in the closet or attic. To help pinpoint a colony, pyrethrin aerosols may be used to flush ants from voids or other harborages. Flush voids in porch columns, hollow beams, cracks along soffits and next to fireplaces and similar suspect locations.

Where “tramp” ant species are involved — such as Argentine, ghost or crazy ants — any pile of leaves, items piled on the ground, sprinkler heads, palm fronds, leaf litter in tree branches, and soil under and along pavement, gravel, stones, and tree trunks/roots could harbor a subcolony. Indoors, colonies may be located under carpeting by doorways, in walls, and with insulation in crawlspaces or attics. Such pest species are the most difficult to control as the number of subcolonies that might be present can number in the dozens on some properties and finding and treating as many of these as possible is important to stopping ant invasions inside.

PRE-BAITING. In many cases, placement of pre-baits at points along the exterior of a building will reveal unknown colonies of the target ant and other pest ant species. Pre-baiting involves placement of small amounts of a jelly, honey or a gel or granular ant bait to corners, window sills, hose bibbs and similar sites. This can be done during the course of the initial inspection when checking things like under stones and leaf litter. Checking back in 5 to 10 minutes will often reveal activity with foraging ants establishing trails that can be traced back to the colony location. Such sites also serve as an indicator of where to establish bait placements/stations.

FOLLOW GUIDELINES. Ants follow structural guidelines, such as edges and corners, for most of the foraging trails between food resources and the nest and between subcolonies. Look for ants foraging along the edge of a sidewalk, the mortar line in bricks, corners and soffits. Once ants are found, look ahead to see where that structural guideline breaks and go to that point. If the trail makes a turn, again look ahead to see where that guideline breaks. If the ants aren’t at the break, backtrack and see where they veered away from the guideline.

I once traced an acrobat ant invasion of a six-story office building by going outside to find the point where the ants were entering; then I would see which direction the ants were trailing along an edge next to the foundation. At that point, I stood turning to look in that direction for the likely site for these ants to nest. The only nesting site in this case for the wood-loving acrobat ant was a large tree. I went to the tree to find a huge ant trail heading up into some dead branch or tree hole high up the trunk. I traced the ant trail backwards, finding the ants followed a structural guideline of some type 85 percent of their 105-foot foraging trail from the tree base to the building. By knowing my target ant preferred nesting in wood, I was able to more quickly determine the source by focusing on the most likely nesting site in the direction the trail was heading.

TREAT THE COLONY. Treating colonies directly gives you the fastest results. The hard part in ant control is finding the colony, especially for species that form satellite colonies or extended colonies with many subcolonies (which is most pest species). Colony treatment is effective because you target the queen(s), the brood, and the majority of the workers. The trick with stopping difficult-to-control ants, such as Argentine, crazy, or odorous house ants, is the possibility of so many subcolonies on the property and the fact that treated areas can be repopulated from colonies on adjacent properties.

Targeting colonies can take time when dealing with ants that have many subcolonies on a single property. Finding and treating as many colonies as possible to all sides of a property decreases the likelihood of these ants invading the inside of a customer’s home or business. With Argentine, crazy and similar ants, eliminating colonies outside in the spring helps keep the populations lower when entering the peak ant season in July and August when ant numbers are at their highest. Gaining the customer’s help to reduce conducive conditions on the property early in the year also helps to lower the ant potential on a given property.

Perimeter treatments to foundations can be beneficial in ant management but should not be depended upon as the sole strategy for ant management. Argentine ants and tawny crazy ants, for example, have been shown to wear insecticide-free pathways through treated zones thus allowing foraging ant trails to invade indoors. Use perimeter treatments as one part of your ant management program. It is still key to find and treat colonies directly.

Applications using residual products (non-repellent insecticides, dusts, foam) labeled for ant control into exterior cracks and potential entry points is another component in preventing ants indoors. Spot treatments along edges of soffits, eaves, exterior window sills where ants might enter also may be used in some cases depending on the type of ant and where it is being seen. Follow label directions as restrictions as to where many insecticides can be applied outdoors have been added to product labels.

BAITING. The industry has a great number of excellent ant baits available but no single product is right for every situation. Some pest ant species do not respond well to feeding on baits and even in those species that readily feed on baits, diet preferences change during the season. This is why professionals should carry a variety of ant baits (gels, granulars, etc.) and offer a “buffet” to target ants to see which bait that colony prefers.

Except in the case of Pharaoh ants, baits should not be the first choice in controlling ant infestations, instead serving as one component in your overall program. The inspection should (1) determine where ants are active, (2) find active ant trails, and (3) identify locations of one or more colonies. Baits can be used where colonies cannot be located such as indoors, where ant trails disappear into walls or voids, or outside after any colonies found are treated.

Indoors, ant trails can be removed by wiping with a soapy, wet cloth back to where they disappear into a wall. This is the point at which you may place ant bait, inside the wall, in an electric outlet box or in a refillable station (secured from contact by children or pets). Outside, place baits at several points along ant trails. If you have time, wait until ants have fed on bait and follow those ants to find the colony so it can be treated. Again, offer two or three different baits and see which the ants prefer.

SUMMARY. Ants are dynamic pests in that ant colony behavior is constantly working to grow the colony and find and exploit new food resources. Each ant species has its own habits and behaviors that need to be understood to find and treat colonies directly wherever possible. Use your knowledge and experience to look at buildings and landscaping to quickly determine the most likely sources for your target ant and begin there. Don’t stop when you’ve found one colony; there are likely more, plus you might find colonies of other ant species before they invade the building. Target treatments to sites where colonies are located or ants might enter. Use baits in conjunction with residual treatments and seek to learn from each ant situation you encounter.

The author is founder of Stoy Pest Consulting, Lakeland, Tenn.