The New Termite Killers

New, non-repellent termiticides seem to be performing differently than their predecessors and new information suggests that these termite-killing materials may indeed be special. By Michael F. Potter and Anne E. Hillery

For most old-timers in the subterranean termite business, it’s been a long and painful decade. Gone are the days when products lasted 30+ years and — for whatever reason(s) — were more "forgiving" than their
replacements. Sure, there were problems with chlordane, but most industry veterans and long-time termite treaters maintain that retreats were fewer and farther between.

Until recently, most post-chlordane termiticides were either organophosphates (OPs) or synthetic pyrethroids. Although the effect of these chemicals on termites is different, the manner in which they impart structural protection is essentially the same. Both function as barriers and must be strategically placed to block all potential routes of termite entry. Barrier treatments do not significantly diminish termite populations in soil away from treated areas. Foraging termites are merely prevented from entering the structure and are forced to find food elsewhere.

TERMITE KILLERS. The recent trend in termiticide development has been products that are non-repellent and lethal to large numbers of termites in the soil. Premise® (imidacloprid; Bayer Corporation) was the first liquid termiticide to work in such a manner and reports from the field have been quite positive. Another non-repellent, Termidor® (fipronil; Aventis Environmental Science), was introduced this spring and Phantom® (chlorfenapyr; American Cyanamid) is in advanced development. All of these products reportedly create a non-detectable treated zone that functions not as a barrier per se — but as a "killing field" — whose effects may be transmissible to other termites in the area. But will such products be more consistent and "forgiving" in the hands of PCOs?

RETREATMENT SURVEY. To help answer this question, we recently compared retreatment rates with Premise to those with organophosphates or pyrethroids on commercial termite jobs. Data were compiled from five independently owned pest control companies in Kentucky and Ohio that were willing to share their customer retreatment records. Companies selected had been using Premise on the majority of their termite jobs for at least one year, subsequent to using organophosphate and/or pyrethroid products.

Only complete, initial applications made prior to 1999 were included in the analysis, i.e., no "spot" (partial) treatments or retreatments. Most were to single-family residences of varying construction.

For each company, the average annual retreatment rate (as a percentage) was calculated for Premise and for whichever product(s) the companies were using prior to Premise. This was done by dividing the total number of jobs treated with a particular product one year into the number of jobs requiring retreatment the following year. (For example, if a company did 100 termite jobs in 1997 and 10 required retreatment in 1998, the retreat rate would be 10 percent.) If a company had used Premise for more than one year, retreatment records were compiled for an equivalent number of years for product(s) used prior to switching to Premise. (For example, if a company used Premise in 1997 and 1998, data for alternative product(s) were compiled for 1995 and 1996.)

RESULTS. Results of the retreatment survey are presented in Figure 1 above. One year after initial application, all five companies experienced a significant reduction in retreats with Premise, compared to whichever product(s) they had used previously. The average annual retreatment rate for the 1,174 total jobs treated with Premise was 5.7 percent vs. 21.8 percent for the 1,193 jobs treated with organophosphates (chlorpyrifos) or pyrethroids. This represents an almost 4-fold reduction in retreats with Premise and was highly significant (P < 0.0001) in a chi-square statistical test. Retreatment rates were similar for chlorpyrifos (18.3 percent, 431 jobs) and pyrethroid products (23.8 percent, 762 jobs).

Dr. Doug Mampe (DM Associates) reported a similar reduction in retreats with Premise in the Northeast. Upon reviewing the retreatment records of five New Jersey pest control companies, he found more than a 2-fold (50 to 66 percent) reduction in retreats with Premise vs. the pyrethroid products used previously.

Despite these favorable results, there are still questions about how long Premise will remain effective. Assessing long-term performance was not the main purpose of our survey. However, for the 1,174 houses treated with Premise during 1995 to 1998, retreats remained low through the end of 1999.

TERMIDOR "ZONE-DEFENSE." All of the new, non-repellent termiticides kill termites tunneling through treated soil. The extent to which they impact foraging populations beyond the treated zone and around structures is unclear. Termidor, the newest non-repellent to enter the market, has attracted much interest — in part from being the first product since chlordane to provide 100 percent control at all U.S. Department of Agriculture field sites at all rates (including the labeled rate) in both the concrete-slab and ground-board tests. Preliminary lab and field experiments also suggest that Termidor may have effects on termites foraging away from treated areas.

Last summer we initiated a study to investigate this possibility and what it could mean to termite control. While it must be stressed that our findings are preliminary, our results suggest that big changes may be in store for how treatments are performed in the future.

The question we wanted to answer was whether a non-repellent liquid termiticide, such as Termidor, could afford structural protection mainly by trenching and rodding around the outside of a building. If the effects of the "perimeter application" were transmissible to enough termites foraging in the area, perhaps we could suppress populations enough to allow the same type of non-intrusive treatment that has become so popular with baits.

To test this idea, we selected a tobacco barn in Paris, Ky., that was heavily infested with the Eastern subterranean termite, Reticulitermes flavipes. Tobacco barns are excellent structures for evaluating experimental treatments. There are no occupants concerned with whether the treatment is going to be effective and since most barns have never been treated, they are often heavily infested with termites. In addition, floors are usually bare soil and littered with cellulose debris, enabling establishment of monitoring stations both inside and outside the structure.

A representation of the barn treated with Termidor is shown in Figure 2 (pg. 59). Dimensions of the main section are 96 feet by 48 feet, with an attached 20-foot by 22-foot stripping room with wood floor on grade. No foundation is present around the perimeter and in most areas, the wood siding was in direct contact with the ground. Structural support is afforded by 10-inch diameter wooden poles on the interior, driven into the dirt floor. Active termites were found in four different above-ground locations inside the barn and in many pieces of wood debris littering the floor.

Eight, long-term monitoring stations were established inside the barn in areas where termites were feeding in wood debris on the ground. The purpose of the monitors was to assess what effect, if any, an exterior Termidor treatment might have on termites away from the treated zone. In this respect, the procedure used was similar to assessing the effects of baits on termite populations. Monitors consisted of large wooden blocks (5 inches long by 5 inches wide by 3½ inches tall) assembled from six pieces of wood separated by toothpick-diameter dowel rods. The blocks were set in place over active termite foraging tunnels emerging from the soil and covered with a plastic bucket weighted down with a stone. An old section of stump, resting upright on the ground and heavily infested with termites, served as yet another monitor of activity.

The nine monitoring sites were inspected monthly or bimonthly and the number of termites observed at each was estimated by assigning a population rating: 0 = no termites present; 1 = 1 to 10 termites; 2 = 11 to 100; 3 = 101 to 500; 4 = 501 to 1,000; and 5 = greater than 1,000. Termite consumption of wood within monitoring stations was measured by periodically removing the wooden blocks and washing, oven-drying and weighing them, relative to their initial weights.

The Termidor treatment was applied by a local pest control firm in July 1999. A narrow (4-inch by 4-inch) trench was dug around the outside perimeter of the barn and around each interior support pole, into which 0.06 percent Termidor 80 WG was applied at 4 gallons per 10 linear feet. A total of 150 gallons was applied (Figure 4).

RESULTS. At time of treatment, termite foraging in the barn was intense (Figure 5, pg. 62). Seven of the nine long-term monitoring sites had termite counts in the thousands and it seemed as if every wood scrap lying on the ground had termites as well. However, at 45 to 60 days post-application, populations within monitoring stations began to decline and a little more than three months after application, no live termites were found at any of the monitoring sites. What we did find, inside several monitors, were tremendous numbers of dead and dying termites (see photo on pg. 54). Scavenging amongst the termite "carnage" were phorid flies, sowbugs, millipedes and free-living mites. Wood consumption within the monitoring stations also declined and 3 to 4 months after treatment there was no more feeding (Figures 3a and 3b, pg. 60).

As of May 1, 2000, all monitoring sites remained termite free and no additional termites have been found any where in the structure or in any of the wood debris lying on the ground.

These results are remarkable, considering the degree of termite pressure in the barn at time of treatment — and that Termidor was applied only around the exterior. All nine monitoring sites and infested wood scraps were on the interior of the building and away from treated soil. The distance between monitoring stations and treated soil ranged from about 1 to 10 feet, suggesting that the product has a significant impact and "sphere of influence" on termites foraging outside the treatment zone. In short, the result was similar to what you’d expect to see with an effective termite bait — only faster.

FUTURE IMPLICATIONS. Our preliminary findings support the notion that the new generation of non-repellent, liquid termiticides are indeed special. The retreatment survey lends credence to anecdotal reports from the field that retreats are lower with Premise. Lowering one’s retreatment rate 2- to 4-fold translates to a significant savings in the bottom line — not to mention a pest control company owner’s peace of mind.

For more than a decade, the industry has judged barrier-type termiticides largely upon "years of protection" afforded in small plot, USDA field tests. While these data are still very important, the ability to stop termites from continuing to infest a structure may be even more crucial.

No matter what product you use, the most common reason for retreats is not because the termiticide degraded — but because we failed to deliver the chemical to the termites or termite entry point(s). This should come as no surprise, considering that termites infesting our wood monitoring blocks were emerging from holes no bigger than pinheads at the soil surface. Also, with today’s construction challenges (combination structures, rigid foam board insulation, stucco below grade, wood and tile floors, sub-slab heat ducts, etc.), it’s become all but impossible to achieve continuous coverage in the myriad of hidden locations where termites may enter. While equipment and training have improved, today’s "free-agent" employees seldom stay around long enough to become skilled termite technicians. Facing these and other realities, companies may be better off using products that are more "forgiving" (having a greater margin for error), regardless of how long we think they might last.

Stopping termites from the outset may also have additional, though unproven, residual benefits. Once the original points of entry are denied and the above-ground infestation is eliminated, the rest of the termite population may not return and reinfest for years.

A BIGGER BAZOOKA. Our preliminary findings with Termidor suggest that the new non-repellents may be more forgiving than anyone had imagined. Judging from the effects on termites in our monitoring stations, it appears that the product is performing much like a "zone defense" in a game of basketball, i.e., the structure (basket) is protected even though there are areas of soil (basketball court) left unprotected.

Just how forgiving are the new nonrepellents? In our test barn, Termidor seemed almost bait-like in its effect. While it is far too early to assume that Termidor can consistently eliminate entire colonies, the fact that we were able to kill satellite units of termites in our monitors up to several feet from the treated zone is amazing. Imagine the benefits this might provide for eliminating termites foraging in inaccessible areas...it would be like having a termite-killing bazooka.

Assuming that our findings are repeatable and the new products are functioning not as barriers but as "killing fields," we again pose the question, "Why must every inch of every conceivable termite entry point be treated?" (See "The Changing Face of Termite Control" Part II, PCT, March 1999). The day may not be too far off when companies no longer have to drill and treat customers’ floors and walls by the tape measure and impediments such as foam insulation and stucco below grade become non-issues — at least in terms of them being safe havens for termites. If the data show that we can protect a home by establishing treated zones in critical, non-intrusive areas, e.g., by thoroughly trenching and rodding the exterior, supplemented by selective spot treatments to infested interior areas, it could revolutionize termite control.

Our intent in writing this article is not to imply that organophosphate and pyrethroid termiticides are ineffective. Indeed, many companies that have been using them for years report relatively low callback rates and satisfied customers. Nonetheless, the performance of true, "barrier-type" termiticides will always hinge upon gaining thorough coverage in the precise locations where termites are entering. Consequently, their level of effectiveness will vary from job to job and company to company.

It’s too soon to know whether the new nonrepellents will end the need to drill floors, drag hoses through the house and pump large volumes of termiticide inside homes. But one thing is certain: the new termite killers are once again bringing interest and excitement to a form of treatment that many predicted would go the way of the dinosaur.