Editor’s Note: The PCT Field Guide for the Management of Structure-Infesting Ants has sold more than 30,000 copies since first being introduced in 1992. Now in its Third Edition, this handy field guide — authored by renowned entomologist Stoy Hedges — has been updated to include the latest biology and control information for the most commonly encountered species of ants in North America. In this third installment of his recently published book, which can be ordered at www.pctonline.com/store, Hedges describes the merits of situational ant management.
Ants are one of the most, if not the most, common insects infesting buildings. In some parts of the United States, certain ants are considered the No. 1 pest in urban and suburban settings (e.g., fire ants in Texas, Argentine ants in parts of Southern California). A good many pest management professionals express frustration in trying to resolve customers’ problems with ants. Much of this frustration may derive from a lack of understanding of different ants and their biology and habits. This article will outline the basic strategies one might use to successfully tackle structural ant infestations.
SITUATIONAL PEST MANAGEMENT. The process used to control ants is basically no different than that used for any other pest. The five steps to follow are the same, only the situation in which they are applied changes. An Argentine ant infestation in a home often will be vastly different from the same ant infesting a hospital. The buildings are different in construction, age, etc., and the conditions contributing to the infestation will be different. The service professional must gather information regarding each situation and then apply his or her knowledge and experience to solving the problem at hand. Situational pest management has the following five basic steps:
Step 1 — Identify the Ant. Many persons attempting to control ants may make the basic mistake of failing to identify the ant or ants involved. "An ant is an ant is an ant. Right?" More than 45 different ant species are considered pests in the United States alone. The Third Edition field guide covers most of those species and provides easy-to-understand tips for identifying pest ants. Most ants are very small, so a 10X to 30X magnifying device is useful to see the identifying characters.
Step 2 — Find Where the Ant is Living. Each ant has its own peculiar biology and habits. Some ants are soil-dwellers while others prefer to nest in wood. A few pest ants only live outdoors while the Pharaoh ant primarily lives indoors. Once the identity of the ant involved is known, then its biology and habits are known. In some cases, two or three different ants may be found infesting the same building. Each ant will be found nesting in different sites. The trick is to determine where in and around the structure that particular ant is likely to locate its colony or colonies. In the case of the Pharaoh ant, however, correct identification leads one to look not for the colony location but rather for the location of foraging trails where baits can be placed.
*****
The Role of
Contributing Conditions
Moisture and dead wood are the two primary conditions present in and around structures that contribute to carpenter ant infestations. Structures that are located in wooded areas or on wooded lots have plenty of both and, therefore, have more potential for problems with carpenter ants. Structures without many trees on the property, however, also can experience carpenter ant infestations. This is particularly true if the structure contains numerous sites with excessive moisture.
If conditions that are contributing to the infestation are not corrected, the carpenter ant problem may not be eliminated or will return soon. Correcting these conditions is the most important step in the long-term management of carpenter ant infestations, but to be successful customer cooperation is essential. Brief descriptions of the most common contributing conditions follow;
Moisture. Moisture is a key to survival for carpenter ant colonies. Water leaks from faulty plumbing or roof leaks provide moisture for ant colonies. Even long after the leaks have been repaired, the moisture may remain if the site is not ventilated or the water-soaked wood is not replaced. Any leaks that are present must be repaired. Carpenter ants can continue to live in the wood even after the leaks have been repaired.
Gutters. Another source of moisture occurs when gutters along the roof line are damaged or become clogged with debris and overflow during heavy rains. The water from overflowing gutters soaks into the fascia boards behind the gutters and into the soffits (eaves) and roof sheathing under the shingles. This problem may go unnoticed for several years, creating a large moisture problem in the wood in this area, thus providing an ideal carpenter ant nesting site.
An examination of the fascia boards and soffits may reveal peeling paint, moisture stains, warping, or the presence of fungi if moisture problems are present. Close examination using a ladder and a moisture meter will confirm visual evidence of excess moisture conditions. Gutters should be inspected to determine if they are clogged. If gutters are clogged with debris, they must be cleaned to allow proper flow of rain water. Gutter screens should be installed to help prevent future clogging problems.
Attic Ventilation. Attic ventilation plays a major role in moisture problems and carpenter ant infestations. Soffits under the eaves must be examined for the number of soffit vents present. If no vents or only a few vents are present, the attic more than likely has inadequate ventilation. Such an attic maintains a relatively stable humidity level that many insects, including ants, prefer. In addition, inadequate ventilation, coupled sometimes with clogged gutters, can result in ice dams in colder climates. When ice dams form, ice may be forced back up under the shingles, resulting in the wood sheathing and soffits underneath being soaked with water when the ice melts.
Poor ventilation supports carpenter ant infestations and must be corrected by installation of more soffit vents and possibly a ridge vent. Ridge vents extend along the peak of the roof and maximize ventilation to all areas of the attic.
Crawlspaces. Crawlspace ventilation and drainage may also play major roles in carpenter ant infestations. A damp, or wet, and poorly ventilated crawlspace creates condensation on wood members. This condensation eventually seeps into the wood making it very attractive to carpenter ants. The presence of fungi or molds on the wood indicates the moisture content is high and may indicate poor ventilation or poor drainage around the foundation.
For proper ventilation, the number of foundation vents should be approximately one vent for each 15 to 25 linear feet of foundation wall. A crawlspace that is shallow (has low clearance) requires more ventilators to provide adequate ventilation (e.g., one vent per each 15 linear feet). Vents need to be installed in all walls of the foundation, if possible, to provide cross-ventilation. Vent fans are also beneficial in very wet crawlspaces.
In cases where excess moisture conditions are present in the crawlspace, the soil surface should be covered with a plastic sheet (vapor barrier). As a rule, no more than 75 to 80 percent of the surface should be covered; otherwise the wood may dry too quickly, resulting in cracking and warping.
If standing water is present in the crawlspace, a drainage problem may be present. The customer may want to employ the services of a company which handles drainage problems to look at the situation. Re-grading, excavation, pea gravel, sump pumps, permanent fans and dehumidifiers are all methods that might be employed to correct such a situation. WARNING!! Avoid entering a crawlspace containing large amounts of standing water. A threat of electrocution exists if live wires are present. Only enter the crawlspace when the standing water problem has been corrected.
Drainage. Concrete patios and porches, in addition to wood decks, are sometimes improperly installed and slant towards the building’s foundation. This slant directs rainwater toward the foundation where it can soak into the siding, sill plate, and box header above the foundation wall. These areas can be checked for high moisture levels using a moisture meter. Carpenter ants can often be found nesting in wood or wall voids behind decks and porches that slant back toward the foundation. If these conditions are present, the customer may want the situation checked by a company specializing in drainage problems.
Dead Wood. Outside, carpenter ants can be found nesting in any dead wood, such as tree limbs, stumps, and firewood. As much of the dead wood as possible on the property can be removed to reduce the potential nesting sites for carpenter ants.
Firewood should be stacked off the ground and as far from the structure as possible. Stacking firewood off the ground and covering it with plastic helps keep it dry and makes it less attractive to most pests, including carpenter ants. Storing the wood as far from the structure as possible prevents carpenter ants, which may be living in the wood, from easily entering the structure. If carpenter ants are living in the firewood, the infested pieces of wood should be thrown away or burned. Avoid treating firewood with any residual insecticides.
When firewood is brought onto the property, carpenter ant colonies may be carried along with it. Advise customers to carry only enough firewood into the structure at one time that can be burned within a few hours.
Tree Limbs. Tree limbs that brush the structure provide ready "highways" for carpenter ants to enter the building. Limbs which reach the structure should be trimmed back away from the structure.
Most of the previously mentioned contributing conditions for carpenter ants will be corrected by the customer. The service professional’s job is to recognize the conditions and educate the customer of the role these conditions play in their ant infestation. Recommendations for correcting these conditions should be presented to the customer both verbally and in writing. The customer needs to be convinced of the importance of correcting these conditions, otherwise your company’s ability to control the carpenter ant problem will be severely compromised.
*****
Step 3 — Direct Control Measures at the Harborage Sites. Once the colony is found, treatment can be directed at that site. In many cases, more than one ant colony is present so several sites will require treatment. With ant colonies, few nonchemical control techniques will be effective by themselves and insecticide treatments of one type or another are necessary. Exclusion to seal out foraging ants is one nonchemical technique commonly used for ants. Installing proper ventilation in attics and crawlspaces to help control carpenter ants is another. In addition to nonchemical control measures, PMPs have a range of chemical control options at their disposal. Always read and follow label directions prior to use.
Step 4 — Correct Contributing Conditions. Any condition that is supporting an ant infestation must be removed or corrected in order to achieve long-term relief from the ants involved. A good example is removing moisture sources within a home as part of a carpenter ant management program (see related story, right).
Step 5 — Follow-up to Evaluate Results. A follow-up visit or phone call can be used to see if the customer is satisfied with the results of the service. Follow-up is especially important when using baits for ants. (This is explained in detail in the Third Edition of the PCT Field Guide.) If an ant infestation continues, generally it is because one or more colonies may have been overlooked. Follow-up permits the evaluation of what worked and what did not so additional efforts can be directed where needed.
CONCLUSION. Any professional who applies the aforementioned five steps to any ant infestation should be successful most of the time. Correct identification of the ant involved is a primary key to finding where the ants are living. Follow-up can ensure the results meet with the customer’s satisfaction.
The author is technical director of Terminix International, Memphis, Tenn., and a frequent contributor to PCT magazine. Contact him at shedges@giemedia.com.