Talk to most pest professionals in any area of the country and they’ll tell you their most problematic pest is ants. Of course, the pest ant that gives each the most trouble differs from state to state and even within a state. In Florida, a particular species such as the Caribbean crazy ant, Paratrechina pubens, may be neighborhood specific and prove to be extremely difficult to control.
In addition to P. pubens, other exotic species continue to emerge, such as the Chinese needle ant, Pachycondyla chinensis, in the Carolinas, Virginia and Georgia; and the European fire ant, Myrmica rubra, in Maine and Massachusetts. The odorous house ant, Tapinoma sessile, continues to increase its range as a structural pest in the Midwest and Northeast. It’s no wonder some professionals find themselves on the defensive when it comes to protecting their customers’ homes and businesses from ants.
A considerable amount of information is available on structural ants on the Web and in publications such as The Field Guide to Structure-Infesting Ants (which will be updated soon, see www.pctonline.com/store). A great deal of the knowledge pest professionals need to be successful in keeping ants out of buildings is gained through field experience, letting the ants, in a way, be their teachers. This article will attempt to boil down this information into 10 tips or principles that factor into being an “ant man” your customers can depend on to keep their homes and buildings as ant-free as possible.
NUMBER ONE: KNOW THY FOE
If you’ve been in this business a while, you may be tired of hearing, “First, you’ve got to identify what you’re dealing with.” It’s what I like to call Entomo-LOGICAL pest management in that all the logic you use to find the source of an infestation is found in the identity of that pest and its habits and biology. With more than 40 different species of ants that invade structures in the United States, this lesson cannot be stressed enough. Professionals can — and do — successfully eliminate or control ant infestations when they don’t know the ant species involved. Knowing your foe, however, helps the PCO be more efficient and successful more of the time.
Likely the most difficult thing asked of pest professionals, who typically have little or no entomological training, is to identify insects and other arthropods. There’s a reason entomologists spend four years studying arthropods and their morphology and classification. Taxonomy is a highly technical field. But one doesn’t need to be an entomologist to learn the basics of distinguishing between the few to a dozen pest ant species in their area that they’re likely to encounter. All it takes is a little instruction, some practice, a good hand lens and reference materials that can be used in the field.
FOCUS ON FINDING COLONIES
The key to success against ants is finding and then directly treating the colony or colonies involved. Finding colonies is the most difficult task facing the professional for several reasons:
- Ants are cryptic in nest habitat selection. They like dark, protected sites in which to nest.
- Colonies can be located in sites inaccessible to reach or investigate.
- Many species have multiple nest sites tied together by trunk trails.
Treatments focused solely on foraging worker trails generally contact only 10 to 15 percent of a colony. Plus, if the pest ant involved has multiple nest sites, are such treatments actually contacting trails leading to all nests? With species such as the Argentine or Caribbean crazy ant, which have huge populations, ants can wear thin sections through treated areas where the pesticide is removed. Thousands die, but many more thousands remain.
When treatments are directed at penetrating an entire colony or subcolony, all the workers, queen(s) and brood are killed, and returning workers also contact the treatment. Treating ant trails leading from the nest to the structure further protect the building from invasion. The “trick” is finding and treating as many colonies as possible to crash the population that is in close proximity in or around the structure.
Situations are encountered, however, where the colony may be inaccessible to treat, such as high in a tree or on an adjacent property. In such cases, treatment of the trails leading up to your customer’s home or business can stop intrusion. Retreatments may be necessary to limit further invasions. Ant baits also may be beneficial in such cases.
KNOW YOUR TARGET ANT'S HABITS AND BEHAVIOR
Just like people have a preference as to where they’d like to live and in what type of house, ants choose nest sites based on what’s best for them. If you are dealing with an ant that prefers to nest in wood, then spending time looking in brick piles, for displaced soil, etc., is not good use of your time.
As a general rule, the following ants prefer the following nesting locations. The third group contains most of our most difficult species.
MOISTURE IS YOUR FRIEND
Service professionals have tough jobs. Daily they have a number of customers to visit and this often limits the amount of time that might be available to service each home or business. PMPs, therefore, need to be efficient in finding the sources of pest infestations in order to have a productive day yet still meet their customers’ expectations.
To quickly find ant colonies, moisture is a key. Carpenter ants and acrobat ants both need moist, dead wood in which to nest. Fire ants and pavement ants prefer moist soils. Argentine, odorous house and crazy ants will locate nests in any “structure” or harborage that is sufficiently moist. For example, a pile of moist leaf litter is more likely to house ants than a pile of dry leaves. Sprinkler heads and water meter boxes often house ants because they retain or contain moisture. Heavy vegetation that sits against a foundation, a tree or a patio wall will trap moisture and is a good spot to check for a subcolony of Argentine, odorous house or crazy ants. Underneath potted plants also is a great site to check for ant colonies as well as in the soil of the plant.
As you inspect, look for piles of items (mulch, soil, etc.), that appear moist. Look for signs of excess moisture on buildings such as stains, molds or peeling paint. Inspect such sites for ants. By allowing your eyes and experience to recognize probable nesting sites, you save time in discovering sources for an ant infestation. Additionally, you’d be surprised how many other ant species you might uncover outside that are not actually invading the structure at that time.
STRUCTURAL GUIDELINES ARE ANT LIFELINES
Another key to focus on is looking for ant trails along structural guidelines. Guidelines on which ant workers establish trails occur where any linear edge or curve is formed. Examples include any corner of wood, siding, pavement and hoses, wires and cables.
Backtracking a trail along structural guidelines from the site where ants are seen inside or entering a building is a way to quickly locate the offending colony in many situations. Once worker trails are located, the PCO can follow the structural guideline being used. Look for the juncture with another guideline and then follow ants to where they enter the building or where they might be nesting. In some cases, if you look in the direction in which the ants are heading, you might see a probable nesting site. Go to that site and investigate — often a colony is found that can be treated.
IS YOUR TARGET SPECIES POLYDOMUS?
Few ant species that invade structures tend to have only a single nest — most are polydomous, meaning they have multiple nest sites. These nests, also called subcolonies, are connected by trunk trails that run between subcolonies and to prominent resource sites (e.g., aphids in landscape plants or a trash can).
Polydomous species generally have multiple queens although some-single queen species, such as many carpenter ant species, also form multiple nests. Pest ant species that typically have but a single nest site include several minor carpenter ant species, most big-headed ant species, pavement ants, fire ants, acrobat ants citronella ants, some field ant species, and cornfield ants. Our most difficult-to-control species are polydomous and include the Argentine any, crazy ants (several species), odorous house, white-footed and big-headed ants (a few species).
When dealing with polydomous species, pest management professionals need to find as many subcolonies as possible in or around the structure. In many cases, these colonies are extended to sites on adjacent properties, thus allowing re-invasion of a customer’s property after treatment. This factor is the primary reason for the difficulty in keeping such ant species out of buildings. The lessons here include not stopping when one colony has been found and extending the inspection to the far corners of the customer’s property. Of course, with a property that is overly large, extend the inspection out within reason.
TREAT COLONIES DIRECTLY
As stated earlier, treating a colony kills more ants than by treating trails alone and it also contacts queens and brood. With carpenter ants, locating and treating the parent colony (usually in moist, dead wood) is the key to successful elimination. With Argentine or other polydomous species, treating one to a few subcolonies delivers a blow to the population and provides temporary relief from inside invasions. Finding and treating many colonies to the edge of the property makes it less likely ants will quickly return to invade the structure.
As you inspect outside, it’s helpful to carry along a sprayer that contains a water-based residual that is labeled for treatment of ant colonies and trails. As you uncover a colony, you can treat it immediately, thus saving a little time. Also, if you didn’t treat it as it is discovered, polydomous species are adept at quickly relocating a nest after it has been disturbed. Come back 10 minutes later and the colony is then gone.
If the ant colony is located within a void then a residual dust or aerosol is typically needed. Small drill holes may be necessary prior to treatment to access the void or ant galleries within wood.
There will be times when location of the colony is not possible or it is inaccessible. In such cases, ant baits can be used as described in number 8. Other strategies may also be employed, including:
- The building foundation may be treated with a nonrepellent, which can kill thousands of workers and reduce the population seen indoors. Such treatment also can be combined with an ant bait treatment.
- Holes or gaps where ants are or might be entering can be treated with another nonrepellent product.
- Ant trails away from the structure may be treated using a water-based residual labeled for application to ant trails.
All of the above may be beneficially employed with direct nest treatments when dealing with extremely difficult species such as Argentine, white-footed or Caribbean crazy ants.
USE ANT BAITS WITH PURPOSE
Ant baits are desirable because they can easily be placed along an ant trail and then the workers do the work, carrying the toxicant back to the colony. In the case of the Pharaoh ant, comprehensive baiting is the most effective strategy due to the unique biology and habits of this species. Locating nests of Pharaoh ants is difficult, so baits are the best course of action.
Baits also may be effective in situations involving some carpenter ant infestations. Pest professionals are using carpenter ant baits successfully in the eastern half of the country, but the carpenter ant species out West have proven more difficult to control. Some companies combine the use of nonrepellents with carpenter ant baits.
For all other ants, finding and treating as many colonies as possible is the most effective way to quickly resolve ant infestations. Relying only on ant baits to control Argentine, odorous house, crazy or other polydomous species that invade from outside often shows limited success. Don’t get me wrong, ant baits are wonderful and effective tools, but they are just that — one tool or strategy we might use. Additionally, a few ant species simply won’t respond well to feeding on ant baits.
Use ant baits with a purpose in mind. For example, when the offending ant colony cannot be located or is on an adjacent property; or, when so many subcolonies are being found, ant baits can be used as an added measure. The point: just placing a few spots of ant bait along a few trails often may not bring the success desired by a customer. Simple guidelines include:
- Follow label directions.
- Offer several baits as a “buffet” to determine which baits the ants in question prefer. Then give them plenty of it.
- Prebait using the ant bait or drops of jelly. Place these outside at corners and edges and check after 15 minutes. Where ants forage on the prebait is where ant baits should be placed.
- Baits should be placed at several locations along ant trails. Locating baits closer to the colony location may improve receptivity.
- Wipe away trails back to where ants are entering and then place the bait there.The workers might decide that where the trail ends is the food source they are supposed to exploit.
- Try liquid ant baits in stations in cases where huge populations are involved outdoors. Liquid bait stations may require weekly visits so keep this in mind.
- Follow up to see if the ants are feeding on the bait or if more, or different, bait is needed. If the ants are heavily foraging on the bait, perhaps the trail is established enough that it can be followed back to the colony location.
GET CUSTOMERS INVOLVED
Any condition that contributes or could contribute to an ant infestation should be pointed out to the customer. The customer needs to understand why correcting such issues will help in long-term relief from ant invasions.
Examples include repairing water leaks; removing piles of lumber, rocks or other items; storing firewood away from the home; trimming back trees and shrubs from the walls and roof; cleaning clogged gutters; clearing out leaf litter (especially under shrubs); and sealing exterior cracks and holes.
FOLLOW UP TO ENSURE RESULTS
Follow up is important in any pest management situation. It can be as simple as the pest professional making a phone call to see if the ants are no longer being seen inside. If ant baits are the primary strategy being used, coming back in a few days to a week or so is helpful in making sure the offending ant colonies have enough bait being fed into the colony food cycle. With white-footed or Caribbean crazy ants, weekly visits by the pest professional may be necessary as these species’ populations can be so huge that constant pressure needs to be put on the infestation to keep them at bay from entering the customer’s home.
The author is a board certified entomologist, professional sanitarian and director, technical services, Terminix International, Memphis, Tenn.
Where Are the Ants?
Soil: fire ant, pavement ant, big-headed ant, citronella ant, field ant, cornfield ant, Chinese needle ant
Wood: carpenter ant, acrobat ant, velvety tree ant
Opportunistic: Argentine ant, crazy ant (several species), odorous house ant, little black ant, ghost ant, Pharaoh ant, rover ant (Brachymyrmex spp.)