In this modern-day Battle of Concord, hydramethylnon baits were used to wipe out a huge population of subterranean termites, thereby saving a historic home from the wrecker's ball.
For more than 300 years, the home of colonial carpenter Thomas Dane in Concord, Mass., has weathered the tests of time and the elements. But over the past 15 years, the historic home has faced another, more sinister challenge one that surely would have tested Mr. Dane's carpentry skills.
Worse than the ravages of wind, rain, snow, sleet and Father Time, the biggest threat to this beautiful home since the early 1980s has been Reticulitermes flavipes the eastern subterranean termite.
The Thomas Dane House was built in 1656, more than 120 years before The Battle of Concord, one of the Revolutionary War's early battles. Additions were made to the house in the 18th, 19th, and 20th centuries. Typical of construction in the colonial period, the oldest parts of the dwelling were placed atop a foundation made of the fieldstones that are common in New England. The foundation base, about 4 feet across and 6 feet beneath the soil surface, tapers like a pyramid to a width of 1 foot just below the 9 x 9 inch oak sills. No mortar was used to join the fieldstones together. Only later were the interior and exterior surfaces of the foundation walls sealed with a coat of cement, adding some stability to the foundation wall and preventing water from entering the cellar. As the house was expanded, new foundations were juxtaposed against old, creating thick stone walls.
The construction and remodeling techniques used to expand the dwelling over the years were not unusual, but the spaces within the dry-laid fieldstone foundation offered termites access to the house's wood frame. And the juxtaposed foundations that were added as the house grew created even more pathways for termites to move unimpeded from the soil to the wood frame.
EARLY SIGNS OF TROUBLE. The current homeowners made an inspection of the house in 1983 shortly after moving in. Some termite damage was discovered, though at the time it was considered to be relatively minor. However, by the late 1980s, the termite damage began to increase noticeably. In 1989 the owners replaced a 9 x 9 inch, 7-foot-long post that was infested with termites in the first floor dining room. Eight months later, they had to replace the post again. Shortly thereafter, termite damage appeared in the flooring of the study and in a threshold between the study and the dining room. Then damage was found on the second floor, where all that remained of a section of wood trim was the coat of paint on its surface.
On Christmas Eve 1990, the owners found that their children's presents, which were hidden in the basement, were riddled with termite tubes and had been destroyed. An antique mirror also was attacked; only the gilding on the ornate frame remained as a reminder of its shape.
The homeowner called several pest control operators to investigate the problem. But after nearly half a dozen inspections, only one bid for $18,000 with no warranty was submitted for the job. The owner eventually contracted with another company, which applied a conventional termiticide around the foundation outside the house. The termite problem remained as bad as ever, however, and the owners continued to search for an effective, long-term solution.
Among the pest control operators contacted to inspect the home was Rod Kreimeyer of Best Pest Control in Arlington, Mass. His 1990 inspection of the home took place after the termites' destruction of the second dining room post. "This was the worst termite problem I have investigated in 25 years in the business," Kreimeyer said. "The termite tubes in the basement were some of the largest I've ever seen. And the dining room post I would not have believed termites could hollow out a post that size in eight months if I had not seen it with my own eyes. It was phenomenal."
PROCESS OF ELIMINATION. Kreimeyer recommended against fumigation, an approach that was suggested by one PCO. He also suggested forgoing construction of a gravel-filled trench around the home, which was another PCO's recommendation. But aside from using his own chemical treatments, which the owners were reluctant to consider because of the ineffectiveness of prior treatments, Kreimeyer felt the solution to the termite problem lay in an alternative treatment. He recommended that the owners call two nearby entomologists to bring a different perspective to the problem.
Drs. Barbara Thorne and James Traniello, two termite biologists, had formed Entomological Associates Inc. in Lexington, Mass. in 1990. Thorne and Traniello had recently discovered a bait formulation for subterranean termites that would make possible the rapid detection of termite colonies and, it was hoped, assist in the control of termite infestations.
Upon inspecting the house, Thorne and Traniello agreed with Kreimeyer's observations that the termite mud tubes hanging from the beams in the basement were the largest they had ever seen. Donning coveralls, the pair moved through crawl spaces to record the extent of the termite infiltration, and probed the sills and beams, finding extensive feeding damage and live termites. The house, they decided, would provide a significant challenge for their termite bait.
The bait formulation is a highly preferred food, not only for the eastern subterranean termite but for a variety of termite species such as other Reticulitermes species and the Formosan termite, Coptotermes formosanus. Subterranean termites forage over large areas that inevitably offer a wide variety of competing foods. To be effective, a bait must "catch their attention" that is, provide the termites with a food that is better than what they are likely to find during their search for food.
The advantage of employing a preferred bait formulation is that when termites encounter the bait, they will "lock on" to it and eat the bait in preference to, or at least in addition to, other available foods. Based on what is known about how other species of social insects forage, termites might even leave a food they were already consuming to collect the bait.
The bait can be used in termite inspections, permitting a PCO to more easily and rapidly detect the presence of termites. (In one instance in Louisiana, the bait formulation developed by Thorne and Traniello diagnosed a termite infestation in one day.) A preferred bait also would be the key component of a bait system to deliver a slow-acting insecticide. Hydramethylnon, a delayed-action toxicant from American Cyanamid Company, was known to be effective in baits against cockroaches (Siege Gel) and ants (Siege Fire Ant Bait). Since termites are related to roaches and are social insects like ants, Thorne and Traniello believed hydramethylnon would work effectively against them as well.
In the summer of 1991, Entomological Associates and American Cyanamid began to collaborate in an effort to rid the Thomas Dane House of termites. Laboratory studies quickly confirmed that hydramethylnon could be incorporated into the termite bait at concentrations that would produce an effective, slow-acting termiticide.
GETTING DOWN TO WORK. Beginning in October, 1991, the entomologists began to use the baits containing hydramethylnon to control the termites. Because of the serious structural problems created by the termites infesting the wood framing of the house, controlling the infestation in the structure itself was a high priority, beginning in the basement where termite activity was most obvious. By the end of the year, 34 hydramethylnon baits were prepared in prototype delivery systems and attached to sills, beams, and the walls of the foundation where mud tubes were pervasive and new tunnels were being built.
Within a month, termites had located all of the baits and were actively consuming them. Termite attacks ceased at some of the baits in a matter of weeks, while at some other baits consumption steadily increased. Within a few weeks in the fall of 1991, the level of termite activity in the basement was noticeably reduced by the baiting program.
By March 1992, all new mud tube construction was concentrated at the initial baits. More baits were added, bringing the cumulative number of interior bait placements to more than 80. Throughout 1992, termites continued to feed on the baits, and bait consumption remained high.
By January 1993, existing mud tubes and other previously active feeding sites were inactive no termites could be found and new mud tube construction had stopped. Over the roughly one-year program of interior baiting, with cumulative bait consumption in excess of 1,250 grams, the termites infesting the structure itself had been eliminated. Throughout the rigorous monitoring that has followed through February 1995 by both the homeowner and scientists there have been no signs of termite activity recovering in the interior of the house.
In the summer of 1993, after the active infestation inside the structure was eliminated by the baiting program, the posts, beams, joists, siding, and flooring that had been damaged by termite feeding were replaced by a construction crew. While the house was already jacked up to remove infested sills, a copper flashing was installed between the foundation and the sill to discourage termites from returning to feed on the house through gaps in the foundation fieldstones.
TAKING THE OFFENSIVE. In the spring of 1992, when the ground had thawed and termites again became active, work began on the larger problem of controlling the termite colony (or colonies) that lived in the sandy soil beneath the house. With the presence of competing food (e.g., firewood and downed tree branches) and the vast extent of the foraging range of the colony (or colonies) as mitigating factors, the researchers began an exterior baiting program by placing 34 "diagnostic" baits (baits without hydramethylnon) around the perimeter to assess the termite population in the soil beneath.
Within three weeks, 82% of the baits had been attacked. Some baits contained as many as 4,000 termites, and many of the baits had been totally consumed. Several days after placement, bait consumption rates were as high as two-thirds of a pound at a single site. This result confirmed the homeowners' worst fear: Beneath and around their house was an immense colony that was continually attacking the structurally vulnerable home.
After the termites had discovered the diagnostic baits and termite recruitment was heavy, the control program began with the replacement of the diagnostic baits with baits containing hydra-methylnon around the perimeter of the home in a method of baiting known as "Interceptive Baiting." Interceptive Baiting is not a new idea. The concept is derived from pioneering research by Drs. Glenn Esenther and Ray Beal, two termite researchers with the U.S. Department of Agriculture whose work in the 1960s established the fundamental principles used in all termite baiting programs being developed today.
With Interceptive Baiting, the termite baits are placed in a defensive perimeter around the infested structure, concentrated in areas of known or suspected activity. Since the bait formulation is a preferred food source, termites rapidly discover and begin to consume the bait. In time, termites actively working in the structure are killed by their exposure to the baits. The goal is to protect the structure from termites, so a primary concern is to eliminate those termites feeding on and doing economic damage to the house. In so doing, however, the larger population that resides in the soil also is exposed to the baits, and is thereby controlled.
Initially, more than 80% of the hydramethylnon baits were attacked, and bait consumption was high. But results showed only a minor reduction in the number of baits being attacked. Baits were replenished as needed around the perimeter of the house, and the termites continued to consume large portions of the toxicant throughout the summer of 1992.
In October 1992, when the exterior baiting program was suspended as the winter weather closed in, termites were still actively feeding in about half of the baits. The exterior baiting program was renewed in May 1993 as soil temperature rose and the termites again became active at or near the soil surface. Within weeks, more than 70% of the perimeter baits were being attacked and, as was the case in 1992, bait consumption was high. There were gradual reductions in the number of baits being attacked, but in November 1993, one-third of the baits were still being attacked by termites, and bait consumption rose slightly throughout 1993.
STEPPING UP THE ATTACK. After two summers of baiting with toxic bait, the researchers decided to conduct an intensive program to monitor termite activity and further define the boundaries of this massive population. In May 1994, diagnostic baits and special monitor traps were placed around the perimeter of the house and also in a concentric ring, 6 to 8 feet away from these perimeter baits. A third set of baits and monitors was placed 16 to 20 feet away, while others were set on an adjacent property.
When the baits and monitors on the property were first checked in June 1994, there was no termite activity at all. Baits and traps showed no signs of termite feeding or tunneling. These baits and traps were replaced and the site was intensively monitored. The result of the continued monitoring throughout the summer of 1994 confirmed the earlier finding: not a single bait or trap was attacked. There now was no evidence of the termites that were once so pervasive. After two years of exterior baiting during the short New England summers a combined total of about eight months during which nearly 2,300 grams of bait were consumed the once massive termite population appeared to have been eliminated.
The results of this program at the Thomas Dane House revealed some interesting and important features of the termite bait control program. In the exterior baiting program, bait consumption consistently increased throughout 1992 and 1993 as baits were replaced. So the addition of hydramethylnon to the bait did not decrease termite feeding, and exposure to a delayed-action toxicant did not cause termites to avoid the baits in the future. These results are entirely consistent with more than 15 years of experience using hydramethylnon in insect control in which the chemical has proven to be nonrepellent and well suited to bait applications.
CIRCUMSTANTIAL EVIDENCE. The results also raise the question of whether or not the termite colony (or colonies) that was beneath the Thomas Dane House was eliminated by the baiting program. Because subterranean termites are hidden in the soil and form large colonies that defy sensible geographic definition, the efficacy of any bait control program must be evaluated on circumstantial evidence. One can examine baits to see whether termites have fed on them, and gauge how much bait has been consumed, as was done in the present study. If termite attacks decline with increasing consumption of the baits, one can assume the decrease is due to the effect of the pesticide.
At the Thomas Dane House, independent monitoring with aged pine stakes and corrugated cardboard traps helped substantiate the success of the baiting program. It may not be possible to dig up a colony to see if it is dead, but the experience in Concord strongly suggests that the baits led to the demise of the termite population.
However, the ultimate test of any baiting program is the residual control of the termites. Continued monitoring at the site in Concord will demonstrate whether hydramethylnon in a termite baiting program already successfully utilized at the Thomas Dane House since 1991 will have the long-term effectiveness required for successful termite control.
Article and accompanying photographs furnished by Dudnyk Advertising & Public Relations, Horsham, Pa.
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TERMITE BAIT TIME LINE • In July 1994, Entomological Associates Inc. is granted U.S. Patent No. 5,329,726 for its "System for Termite Detection and Control." • In November 1994, Entomological Associates Inc. signs an agreement with American Cyanamid Company granting the New Jersey-based manufacturer an exclusive worldwide license to the patented termite baiting system and the termite bait formulation (patents pending). • In January 1995, Cyanamid submits to the U.S. Environmental Protection Agency a registration application for the hydramethylnon termite bait formulation. • Label directions for the product and Cyanamid's termite baiting program are presently under review by the EPA, and will be submitted for review to state regulatory officials. • Field research conducted by Cyanamid, which first began in 1992, is continuing in 1995 and 1996 to define the optimal use patterns and performance characteristics of the termite bait.  Explore the August 1995 IssueCheck out more from this issue and find your next story to read. Latest from Pest Control Technology
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