Inspection: The Key To Successful Carpenter Ant Control

PCOs Can Dramatically Reduce Their Callback Rates For Carpenter Ants By Requiring Technicians To Perform Nighttime Inspections, According To Purdue University Researchers.

A survey of northeastern pest control professionals indicated that nearly half of the 21 companies responding had callback rates on carpenter ant jobs of 20 to 30%; an additional one-fourth suffered alarmingly high rates of 40 to 60%. In this article we will focus on the most important aspect of carpenter ant control: finding the colony.

In the beginning we will present some important principles of carpenter ant biology that will set the stage for the argument that the non-targeted, blind application of insecticides is wasteful for many reasons and is in large part ineffective. We will conclude with some helpful tips on finding colonies located both outside and inside the home.

NESTING & FORAGING HABITS. In the North and Northeastern United States, black carpenter ant, Camponotus pennsylvanicus (DeGeer) (Fig. 2), habitat is characterized by areas abundant in large trees (Fig. 1). Carpenter ants are a nuisance due to their size and abundance and because they chew wood for nest sites. Wood excavation results in the creation of random galleries where brood (i.e., eggs, larvae and pupae) are held during development. This nest type is often referred to as the brood nest.

Sometimes, ants from a brood nest will carry brood to a site nearby and establish a satellite nest. Although the function of satellite nests is only partially understood, we suspect that they may serve as "resource outposts." We hypothesize that one of the primary functions of the satellite nest is to gather resources (i.e., honeydew and dead insects) for the brood nest. The brood nest is where the queen resides and in truly social insects such as ants, life revolves around keeping the queen well fed and safe so that she may produce eggs.

Movement among brood nests, satellite nests and feeding sites is often facilitated by the use of permanent foraging trails (Fig. 3); trails are well maintained by workers and due to the extent of their use take on a "beaten path" appearance. Unlike ant species that forage in a more random fashion and cover much more ground (e.g., pavement ants), carpenter ants forage between nesting and feeding sites along permanent trails and during the season deviate little from the trail. This is an extremely important point to consider when reading the sections on Control Strategies and Finding the Colony later in this article.

In their natural setting, carpenter ant feeding grounds are often limited to the canopy of adjacent trees. In Indiana, we have seen worker carpenter ants travel, along the ground, as far as 120 feet to feed in the canopy of nearby trees. In the canopy, carpenter ants feed on other insects and the sweet, carbohydrate-rich honeydew produced by aphids and scale insects.

Purdue research has shown that carpenter ants are most active at night (Fig. 4) and that daytime activity is very limited. In experiments using electronic counters, the maximum number of ants counted per hour during daylight hours (i.e., 7:00 a.m. to 7:00 p.m.) was less than 10. However, as night fell (i.e., between 7:00 and 8:00 p.m.) ant activity increased dramatically and from 9:00 p.m. until sunrise there were 300 to 400 ants counted per hour. Carpenter ants are nocturnal for a variety of reasons: to avoid predation, to avoid competing with other ant species for resources and to avoid foraging during the heat of the day (a water conservation strategy).

CONTROL STRATEGIES. There are two extremes in carpenter ant control philosophy. Limited, or nonexistent, inspections resulting in failure to find the colony often lead to the aggressive, widespread application of insecticide (e.g., dusts in all voids plus a perimeter treatment). The only advantage, if it can be called an advantage, of this approach is that little or no time is invested prior to application of insecticide. The disadvantages of this approach are many: (1) lack of control leading to callbacks because of the inaccurate placement of insecticide; (2) the added expense associated with wasteful application of insecticide; and (3) the time needed to apply multiple formulations to multiple sites.

In our survey of the industry, 91% of those surveyed use dusts for carpenter ant control; 78% use bait; 70% use wettable powders; 61% use microcaps; 26% use emulsifiable concentrates; and many use aerosolized pyrethrin as a flushing agent. Additionally, 90% of companies indicated that they provide a perimeter treatment as part of their company’s typical carpenter ant control service.

The second philosophy of carpenter ant control is the flip side of the approach discussed above. It involves an up front, thorough inspection that does not conclude until either the colony is found or a best guess can be made as to where the colony is located. Only then should any type of insecticide be applied.

The end result of finding the colony is the focused application of insecticide. This approach can often lead to colony elimination because treatments are placed directly where the ants live. The focused application of an inferior formulation and active ingredient is more effective than the application of a superior formulation and active ingredient that does not reach the ants. Keep in mind that whichever approach your company embraces, it will likely invest a considerable amount of time at some point in the process.

If finding the colony is not an important part of your company’s carpenter ant control program, the time will likely be spent on a callback; if finding the colony is part of your company’s carpenter ant control program, then time will be invested up front during the initial inspection. The saying "You can pay me now or you can pay me later" certainly holds true in carpenter ant control when it comes to time investment. For that matter, it holds true for most situations in pest management: inspection is the key to successful pest control. We do crack and crevice pest control for German cockroaches, right? Why should carpenter ant control be any different? The goal, no matter what the pest, is to put the pesticide where the pest lives. Finding out where the pest lives by knowing where, when and what to look for is what makes our industry unique and exciting.

FINDING THE COLONY. If the key to carpenter ant control is finding and treating the colony, then the inspection is ultimately what determines success or failure. In our survey, all respondents indicated that they make it a point to try and find the carpenter ant colony during inspection, but 82% (i.e., 4 out of 5) were successful half the time or less.

Whether inspecting indoors or outdoors, it is important to spend a few minutes with the homeowner. The property owner can often provide evidence as to location and activity and lead you right to the nest.

Let’s discuss some important topics related to finding colonies located outdoors. Brood colonies, typically located outdoors, are the ultimate root of carpenter ant problems indoors. Ants from brood colonies may be foraging indoors at night and then retreating during the day, or they may have established satellite colonies inside.

Although brood colonies can be found in many habitats outside, in most cases they are housed in large trees on the client’s or even the neighbor’s property. When inspecting trees on a client’s property, seek out and pay special attention to those with tree holes (Fig. 5, pg. 72). Trees containing tree holes – both large and small – should send up a red flag to the service technician that this tree might very well house a colony. Certainly do not neglect other locations (e.g., railroad ties, firewood, tree stumps) when inspecting outdoors, but concentrate your effort on inspecting live, standing trees with tree holes. We have spoken with pest control professionals at the Purdue Pest Control Conference who carry out a successful carpenter ant control program by concentrating all efforts outdoors.

Inspections should be done at night, when carpenter ants are most active (Fig. 4). Our survey, however, confirmed what we believed; 95% of service technicians do not perform night inspections. The easiest way to find a carpenter ant colony is simply to follow foraging ants back to their nest. In the daytime, this tactic is virtually impossible, as only a few ants may be active. Inspections conducted during peak activity hours (i.e., after 7:00 p.m.) oftentimes leads one directly to the nest due to the large number of foragers present and their directed movement to and from the colony along well established foraging trails.

There are two major advantages of conducting night inspections: (1) the success rate of finding colonies is increased, and (2) the time needed to find the colony (i.e., inspection time) is often lessened. During the summer, we spend three to five nights per week looking for carpenter ant colonies for research purposes. On many occasions, the large number of ants present on a foraging trail leads us directly to the colony.

Find permanent foraging trails in the grass (Fig. 3). If just part of the trail can be located, it can be a tremendous help in finding the colony. Most of the time the trail is not as obvious as the one depicted in Fig. 3. As such, a reliable method we use for locating a grass-covered, camouflaged trail is to stare at a particular point on the ground where the trail is suspected and to use one’s peripheral vision to catch a glimpse of ants moving under the grass. Then, get down on your hands and knees and peel back the grass to expose the well-manicured trail. If this is repeated in several locations, a directional pattern of the trail will emerge and lead you directly to the nest.

Indoors, some of the sites that should be inspected for the presence of carpenter ants include: window sills, attics/soffits, hollow doors, crawlspaces/basements, plumbing, bathroom, under siding, dishwasher, gutters, fireplace/chimney, wall voids, behind electrical plates, behind flashing, behind exterior corner molding, in hollow columns and wood railings. Of course, this is not a comprehensive list, but it does convey the importance of conducting thorough inspections indoors. Look for signs of infestation indoors, including sawdust and parts of dead ants. The use of a borescope or stethoscope can be utilized to look and listen for ants in voids.

SUMMARY. Carpenter ant control in the North and Northeastern United States is hampered by the high rate of callbacks experienced by some companies. We believe that this problem is due to a general lack of success in finding colonies because carpenter ants are nocturnal and service technicians rarely, if ever, conduct night inspections. As such, we recommend that night inspections be performed and that large trees be the primary target of inspection. Night inspections will result in a reduction in post-treatment callbacks because of the higher success rate in finding colonies.

Drs. Daniel R. Suiter and Gary W. Bennett can be reached at the Center for Urban & Industrial Pest Management, Department of Entomology, Purdue University, 1158 Entomology Hall, West Lafayette, IN 47907. E-mail: dsuiter@entm.purdue.edu and gwbennett@entm.purdue.edu.