ANT SUPPLEMENT: Carpenter Ant Control: An Outside Job

Effective baits, combined with greater insights about carpenter ants, have led one pest professional to a remarkable conclusion: This difficult pest can be effectively dealt with, for the long term, entirely from the outside of structures.

That’s the belief of Richard Cooper, technical director, Cooper Pest Control, Lawrenceville, N.J. Cooper recently completed a series of research projects examining carpenter ant control using bait outside structures only. His results have led him to conclude that with the right bait and a solid knowledge about carpenter ants, professionals can eliminate callbacks and solve most carpenter ant problems.

Cooper’s presentation at the PCT/Aventis Ant Symposium provided some food for thought to pest professionals hoping to improve their success rates with carpenter ant control.

TROUBLE WITH CARPENTER ANTS. Cooper’s work focused on the behaviors of Camponotus pennsylvanicus, the predominant carpenter ant species in the Northeast. In his area, Cooper said, this opportunistic species is the source of many callbacks. Its multiple nests are difficult to locate and even if nests are found, it can be challenging to get effective penetration of chemical throughout the complex nest site.

"In some cases, there is no nest located in the structure at all and all the ants that the clients are seeing are simply foraging workers coming into structures looking for resources," Cooper said. On the other extreme, he noted, some structures have several nests. "And if our technicians miss even one of these nests during their treatment program, the client is likely to continue to see activity and that will result in more service calls," Cooper added.

Cooper pointed out that a single carpenter ant society consists of a brood nest and its associated satellite nests. Parent or brood nests are typically located outdoors in trees and stumps and are usually associated with areas of high moisture content. As colonies grow, they form satellite nests to meet their expanding needs. These satellite nests tend to be located in much drier environments, with the ants traveling back and forth to brood nest locations via "trunk trails."

"[Satellite nests] tend to be the nest sites that we’re dealing with in structures," Cooper said. However, even if satellite nests are found and removed, homes are likely to experience reinfestations, Cooper said, if PCOs don’t locate the parent nests that are associated with the satellite nests.

But even more challenging than carpenter ants’ nesting habits are their foraging behaviors, Cooper said. "Probably the greatest obstacle we face," he said, "is that carpenter ants are most active at night and we typically perform our carpenter ant control during the day." Cooper cited various studies that have shown a relationship between diminishing light and increased foraging activity of carpenter ants. Research has indicated that during daylight hours, carpenter ant activity is suppressed and unpredictable. But within a half an hour after sunset, there is a rapid peak in carpenter ant foraging activity and it remains high throughout the dark hours.

Ants typically exit structures during the evening hours, following foraging or trunk trails back to brood nests. Therefore, he notes, evenings are a great time to pinpoint ants’ entry points into homes and even to locate brood nest sites. However, Cooper adds, it’s probably not practical for PCOs to do all of their carpenter ant work at night. "I don’t think there are enough nighttime hours in a summer to service the thousands of clients that we have," he said. But, he noted, nighttime work can help solve complex or chronic problems.

Although it’s readily apparent that carpenter ants are most active outdoors, Cooper says there are a few reasons why most professionals continue to focus their control efforts inside structures. "First, I think that our clients expect it," he said. "They’re seeing carpenter ant activity inside their home and as a result, that’s where they expect us to concentrate on control efforts." Secondly, he said PCOs feel compelled to work inside homes because they’re not exactly sure whether the ants seen are foraging inside for resources, or if there’s actually a nest inside the structure. Third, until recently, all available control materials have been based upon contact kill. Conversely, he said that some of the new technology is not based on mortality of the individuals that contact treated areas, but instead affect colonies at the population level.

Considering the limitations of conventional methods and that carpenter ants are most active outdoors, Cooper came up with a new control idea. " I began to examine the possibility of developing an exterior approach utilizing baits as the primary tools," he said.

THE STUDY. Toward this end, Cooper conducted a series of studies examining the control of C. pennsylvanicus using Maxforce gel with fipronil. The first study focused on baiting carpenter ants outdoors, at night, in nine mature trees in a commercial setting. The study began one hour after sunset, when Cooper took pre-counts of carpenter ants foraging in sections near or on trees. He then applied bait along the foraging trails, both in and on trees, using small plastic platforms to hold the bait. Post-counts of the ants were taken at days 1, 3, 7, 21 and 30. "Baits were only reapplied on the subsequent visits if less than 50 percent of the bait was remaining and there was still activity along the trail," he said.

Upon observing the ants’ activity after bait placements, Cooper found they carried chunks of gel back to the nest. "Within about 48 to 72 hours we started to see dead ants appearing at the bases of the trees," Cooper said. This continued for about two weeks.

About 40 days after the study began, Cooper was able to cut down and section the trees and grind the stumps to look for ant activity. "In all but two of the treatments, there were no ants in the trees," Cooper said. "In the two treatments where ants still did exist, neither nest contained brood and fewer than 40 adult ants remained present."

In addition to the nighttime tree study, Cooper also conducted replicate studies on six private residences following the same protocol. "We had elimination of foraging trails entering into the structure within two weeks at all six replicates," he said.

According to Cooper, the studies showed that fipronil is an effective active ingredient for use in carpenter ants baits. However the studies did leave some unanswered questions. "The problem with this is that all these results were achieved during the nighttime when carpenter ants are most active and that makes it very easy to identify trails," Cooper said. "It also makes it easy to maximize recruitment and consumption because you’re placing fresh bait along the foraging trail during the peak foraging period." This led him to consider whether the results could be replicated during the day. So, Cooper conducted a daytime study of 52 properties under contract with Cooper Pest Control. In this more informal study, Cooper sought to treat the structures entirely from the outside.

At each property, Cooper began by conducting a detailed exterior inspection. "Effort was made to try and identify entry points into the structure, foraging trails and possibly nest sites that were in trees that I believed to be associated with the ants that were affecting the structure." Based on those inspections, Cooper made targeted applications of baits to entry points into the structure and to potential nest sites in trees where possible (taking into account whether bait might be accessible by children or pets).

ESTIMATING ANT ACTIVITY. To overcome some of the obstacles of working during the day, Cooper used three methods of estimating ant activity. First he used the "line or edge perspective," which focuses on structural guidelines, such railroad ties, foundation corners or other structural edges, which carpenter ants are known to orient to. "By focusing on those areas you can speed up the amount of time it takes to find the ants that may be outside during the day," Cooper said.

Cooper also used the "vector perspective," also known as "feed and follow." This is the idea that ants forage for food in a ran-dom way, but once they locate a food source, they make a linear path back to the nest site. By offering foraging ants pieces of food, PCOs can try to trace ants back to their nests.

Lastly, Cooper used "gut instinct," to help locate trails and entry points. Since he has logged more than 300 hours of nighttime observations, Cooper says he’s developed a good feel for carpenter ant activity. "You do enough carpenter ant work and spend enough hours out at night," he said, "and you can sort of close your eyes and see it as though it were still nighttime."

The results of the daytime study were "nearly unbelievable," Cooper says. "We had a 94 percent success rate based on service call history," he said. Only three clients out of the 52 requested an additional visit.

To further verify the results, Cooper chose 10 of the structures at random and conducted nighttime observations on those structures on days 0, 14 and 30. "In eight of the 10 structures, the baiting placements made during the day eliminated all the trails coming into the structure," he said. In the other two structures, he was 80 percent successful in locating trails during daytime inspections.

CONCLUSION. While Cooper is pleased with the results of his efforts, he notes that the small population size of C. pennsylvanicus colonies probably has something do with his success. "As a result of being single-queen colonies, their populations are much smaller," he said. Colonies number anywhere from 3,000 to 6,000 ants, compared to upwards of 60,000 ants in carpenter ant colonies indigenous to other areas of the country.

Even so, these results have led Cooper to believe that carpenter ant control will likely change in coming years. "I think you’re going to see a major shift to an exterior approach using baits, non-repellents and other technologies," he said. Furthermore, Cooper said, control will occur at the population level, not at the individual level, as it has in the past. And he predicts there will be a reduction in the need for technicians to enter structures.

But, Cooper says, no matter how effective new products are, PCOs will still need to focus on the basics. "If the conditions that promoted activity in the first place aren’t corrected, these structures will ultimately get reinfestations," he said. Fortunately, he added, it’s likely that more companies will provide comprehensive carpenter ant control programs in the years ahead. "I think we’ll see a trend where more companies are offering total ant management programs," Cooper said, "where we’re working at the population level and we’re addressing the conditions that promote activity around the home."

The author is former managing editor of PCT and can be reached at lmckenna@pctonline.com.