The Changing Face Of Termite Control

Will the rapid rise in baits bring an eventual end to traditional "barrier" treatments and termiticides? Some have been so bold as to predict that, in less than five years, companies will no longer even know how to perform such services. Perhaps. Yet, for the foreseeable future, there will still be a need for fast-acting soil termiticides, such as when responding to swarmer complaints or real estate transactions. A high percentage of companies using baits are also making liquid or foam spot applications to infested areas. Another segment of the industry has chosen to steer clear of baits entirely, and continues to perform conventional treatments as it always has.

There certainly is no shortage of liquid termiticides to choose from. More than a dozen products are being marketed. FMC Corporation’s new pyrethroid formulation, Talstar, (bifenthrin) was introduced late last year. Registration of AgrEvo’s new pyrethroid termiticide, DeltaGard TC, is pending but imminent. Other than Premise, all of the registered products are either organophosphates or synthetic pyrethroids. These traditional product classes continue to perform well in USDA Forest Service trials, and many companies that use them report low callback rates and satisfied customers. Other PCOs contend that they are unable to duplicate the consistent performance results obtained in the Forest Service test plots in their own real-world accounts. This has rekindled interest in the age-old questions of why chlordane was so effective and what characteristics make for a "good" termiticide.

Much of the discussion and debate has come back to the issue of repellency — and whether it is good, bad or irrelevant. It is well known that synthetic pyrethroids are highly repellent to termites. Upon encountering pyrethroid-treated soil the workers do not die but change direction and continue to forage. In comparison, organophosphate soil barriers (i.e., chlorpyrifos) are non-repellent, but foraging termites are killed quickly upon contact. This results in an accumulation of dead termites in a localized area which, according to some researchers, could result in a "secondary" form of repellency due to the chemicals emitted from the decomposing termite corpses. Thus, in the field, the ultimate effect on termites foraging in the vicinity of an organophosphate or pyrethroid-treated barrier may not be so different.

But what about termiticide products that are both non-repellent and slower-acting? Premise fits this description. Reports from many PCOs around the country who are using this product have been quite positive. The overall feeling among Premise users is that callbacks are down and many of their recurrent termite problems have gone away. This is consistent with results of a recent study conducted by Dr. Doug Mampe, comparing retreatment rates for jobs using Premise to those using pyrethroid termiticides. Based on 1,600 termite jobs completed by five different pest control firms in the Northeast, the number of re-treatments performed within 12 months of the original job were 50 percent less with Premise.

Dr. Byron Reid, research product manager for Bayer, attributes the low callbacks with Premise to a combination of factors — foremost being the non-repellent nature of the Premise treated zone. "Because they are not repelled by Premise, termites rapidly become intoxicated and are killed as they tunnel through treated soil. And because the distribution of termiticide in the soil — from the point of application — is greater with Premise than with other termiticides (a process Bayer has termed Lateral Soil Movement), there is less chance of unprotected gaps in the treated zone."

Another reason for the low number of callbacks with Premise may be due to the effect it has on termites above ground. Repellent termiticides can "trap" termites foraging within the structure at time of treatment and prolong the infestation. Because termites foraging above ground are not repelled by Premise, they readily return to the soil, become intoxicated and die. We recently observed this attribute of nonrepellency on a test house in Lexington, Ky., following application of the new experimental product, chlorfenapyr (see "New Chemistry" section). Large numbers of termites had been present within an exterior bedroom wall for several months prior to treatment. High wall moisture readings were recorded from ceiling to floor with no apparent moisture source other than the termites themselves. Within four weeks of applying the non-repellent termiticide to the soil, the termites in the wall were dead and the moisture content of the wall had returned to normal levels. It is doubtful that such rapid results would have occurred using a repellent material. Presumably, the termites in the wall were killed in the process of returning, unimpeded, to the soil.

There is still some concern about how long Premise will last in the soil. In USDA Forest Service trials, the product has performed well through five years in the concrete-slab test. Similar to other registered products, loss of control occurred much sooner (two to three years) in the ground-board test. Considering that the average life of a termite warranty is about four and a half years, many operators are willing to sacrifice extended years of protection for fewer initial callbacks.

NEW CHEMISTRY. At least two other liquid termiticides are well along in the development pipeline, fipronil and chlorfenapyr. Both belong to new chemical classes and have novel modes of action. Similar to Premise, neither product is repellent to termites. First to market will likely be fipronil. Fipronil is a member of a new family of insecticides called phenyl pyrazoles. The mode of action in termites is unique, causing blockage and disruption of the GABA regulated chloride channel and central nervous system. The same active ingredient is already present in Maxforce FC roach and ant baits, and Frontline spray for control of fleas and ticks on pets.

Fipronil was discovered and will be marketed by Rhone-Poulenc, a relatively new player in the structural pest control industry. They are one of the largest producers of insecticides in the U.S. and worldwide. According to Manny Martinez, business manager for Rhone-Poulenc’s Professional Pest Control Group, "the product will have no repellency, outstanding efficacy, and long soil residual. It also has low toxicity, odor, volatility, and use rates, and will be supplied in convenient, ready-to-use packaging." Fipronil is currently in its 5th year of testing at the USDA Forest Service. Through four years, it has continued to provide 100 percent control at label rates in both the concrete-slab and ground-board tests. No other product since chlordane can make such a claim. The company is currently testing fipronil on termite-infested structures throughout the U.S. with cooperating PCOs, state regulators, and university researchers. According to Martinez, registration is anticipated some time in 1999.

American Cyanamid is also preparing to enter the liquid termiticide market with their new active ingredient, chlorfenapyr. Similar to fipronil, chlorfenapyr has insecticidal activity against many urban pests including cockroaches, ants and termites. It belongs to a new class of insecticides, the pyrroles, which cause insects to die by interfering with their ability to produce energy. Because chlorfenapyr affects energy production, it is relatively slow acting, in addition to being nonrepellent.

Studies indicate that termites readily tunnel into chlorfenapyr-treated soil, causing mortality within a day or longer, depending upon concentration and dose acquisition. Because of this nonrepellency and delayed-action mortality, Cyanamid predicts their product will destroy termites attacking the structure as well as others foraging in the area. Chlorfenapyr has been in USDA Forest Service field tests for two years. It is also being evaluated in a nationwide Experimental Use Program (EUP) on termite-infested houses. The product will be odorless and the label will have a Caution signal word. According to Dr. Bob Farlow, manager of North America Product Development, Cyanamid hopes to receive general pest control approval by the end of 1999, with use for termite control pending the outcome of U.S. Forest Service and EUP results.

What can be expected from this trio of nonrepellent termiticides? Will they ultimately perform more consistently and be more "forgiving" than organophosphate and pyrethroid products? While it may be tempting to think so, the research and experience base is still very preliminary. The manufacturers of Premise, fipronil, and chlorfenapyr all talk in terms of a "treatment zone" (as opposed to a barrier) that causes significant mortality to termites tunneling through treated soil, and to other termites in the area. This is beginning to sound a lot like the effects of some termite baits! If it can be shown that one or more of these products causes a substantial decline in termite populations foraging in the vicinity of structures, we may need to expand our thinking to include an entirely new category of treatment... is it a barrier or a bait or both?

Since we’re in a "what if-mode," let’s speculate a step further. Assuming that the treated zone is non-detectable by termites and functions not as a barrier — but as a "killing field" whose effects are transmissible to other termites in the area — why must every inch of every conceivable termite entry point be treated? We certainly do not install traditional baits in this fashion. Perhaps the day will come, supported by adequate data, when companies no longer have to drill and treat customers’ floors and walls unnecessarily, and can achieve a satisfactory level of protection mainly by thorough trenching and rodding of the exterior, supplemented by interior spot treatments to infested or high-risk areas. Such a program would probably warrant quarterly or semi-annual monitoring. Perhaps there’s a future for liquid termiticides after all.

To some old timers and those with regulatory responsibilities, the aforementioned scenario may sound farfetched, bordering on the sacrilegious. But if proven effective, the benefits of such a treatment would be enormous: less disruption to the homeowner, less pesticide applied to the interior, fewer construction woes, etc. In short — many of the same benefits currently achieved with baits — yet with fewer monitoring hassles and the added peace of mind from knowing there is some residual protection in the soil. The public would love it.

OTHER APPROACHES. Although much of the current interest has been on baits and liquid termiticides, other product categories continue to be utilized or are in various stages of development.

Borates. It’s been almost 10 years since the leading borate formulations, Bora-Care and Tim-bor, were registered for remedial treatment of wood in the United States. The largest category of usage has been for prevention and control of subterranean termites. Although some of the former interest in borates has shifted to other technologies such as termite baits, they remain useful and versatile tools in the termite control arsenal.

In most cases, borates are being used as a supplement to other forms of treatment. Where wood is presently infested with termites, Tim-bor and Bora-Care are applied as surface sprays or injected directly into the galleries. Borate-laced foam is being injected into the bottom of wall voids in order to coat the sole plate and lower portions of studs located above expansion joints and settlement cracks, and into the voids behind window and door casings, siding and brick veneer.

Since borate-treated wood normally retains its preservative qualities for decades, companies are also applying Tim-bor and Bora-Care to exposed wood likely to be attacked by termites in the future. Prime targets for preventative treatment on existing construction are along the box-sill assembly in crawlspaces and basements, behind dirt-filled porches, above piers, chimney bases, and rubble foundations, within bath traps, and where pipes, ducts and utilities pass through flooring. Some companies are cooperating with builders and spraying all wood members during the construction process. Such treatments are usually performed when all structural wood and sheathing is in place, but before installation of drywall, insulation, and wiring. At this stage of construction, PCOs can achieve much better spray coverage of vulnerable wood surfaces. Borate penetration into the wood may also be enhanced since wood exposed to the elements continues to absorb atmospheric moisture (see subsequent comments pertaining to moisture and borate penetration).

What will be the impact of such treatments on termites? Research and practical experience indicate that subterranean termites have a difficult time penetrating through, or tunneling over, wood surfaces treated with labeled amounts of borate. In the seventh year of a USDA field study initiated by Lonnie Williams in Mississippi, termites continue to be deterred from tunneling up and over Bora-Care treated floor joists. The study suggests that applying Bora-Care to wood members that subterranean termites are likely to encounter first (e.g., box-sill assemblies, above piers, etc.) may help deter their upward movement into structures.

Despite these useful qualities, there are limits to what PCOs should expect from remedially spraying wood surfaces with borates. Termites tunneling deep within wood are unlikely to be affected unless the wood moisture is at least 25 percent. The higher the moisture content, the deeper borates will eventually penetrate. At a moisture level of 15 percent or less (typical of most structural members), lethal concentrations of borate will be deposited about 1/8 to 1/4 inch into the wood. Older, rougher, insect-damaged wood generally affords better penetration than newer, smooth-surfaced wood that is sound. Another limitation with remedial treatments is that, oftentimes, only one side of a wood member (sills, headers, etc.) can be treated. Unless the moisture content of the wood is high, it is doubtful that termites tunneling over the opposite, untreated surface will be affected.

Ironically, the greatest impact on termites in the future may not be from pest control firms that use borates — but the wood preservatives industry. A growing number of wood treatment plants, aware of the efficacy and environmental advantages of borates, are incorporating them into lumber and other wood-based products. By utilizing vacuum, pressure impregnation or dip-diffusion methods, wood treatment plants can achieve virtually complete penetration and protection throughout the wood member. Assuming that marketing, distribution and cost factors can be overcome, the day may come when a significant percentage of buildings in this country are constructed with borate-treated lumber, as is currently being done in other areas of the world.

Bio-Blast. An excellent review of this product can be found in an earlier article, written by Dr. William Quarles (See "Bio-Blast" PCT, Oct. ’97). Bio-Blast Biological Termiticide has been marketed by Paragon Professional Products since 1997. Because it was the first naturally-derived, microbial pesticide to hit the professional termite market, it has attracted a good bit of attention.

The active ingredient in Bio-Blast, Metarhizium anisopliae, is a common soil-dwelling fungus which is lethal to termites. Infection occurs when the spores germinate, penetrate the termite’s cuticle, and grow inside the body. Mortality occurs within days or a few weeks following exposure. Termites may become infected with the fungal spores during foraging activities, or indirectly through grooming and food exchange with other termites. Because the effect is delayed, other colony members may be killed that never were directly exposed to treatment. In the absence of termites, the fungal spores in Bio-Blast lose their effectiveness in about two to three months; thus, there is no residual protection per se against re-infestation.

According to label directions, Bio-Blast should be mixed with water and sprayed or injected directly into above-ground areas of infestation, e.g., into termite feeding galleries, active mud tubes, Formosan termite nest carton, and voids in damaged or vulnerable wood. The fungal spores do not penetrate wood in the manner of borates, and it is important to contact as many termites as possible to maximize the spread of infection.

What will be the impact of such treatments? As is typical of most termite control products, success in the laboratory is no guarantee of success in the field. Limited field tests with Bio-Blast were conducted by Dr. Brad Kard of the U.S. Forest Service. The results suggest that Bio-Blast can eliminate localized above-ground termite infestations, but re-infestation is likely in the absence of soil treatment. There are no studies indicating the product will eliminate large populations of subterranean termites foraging below ground. Against structural infestations, Bio-Blast’s performance probably will depend on the extent of infestation, and one’s ability to deliver the spores into areas where they will be in direct contact with termites. Based on PCO experiences, the product seems to perform well sometimes, but not others. In summary, while Bio-Blast should not be viewed as a stand-alone treatment, it can be a useful complement to other forms of termite prevention and control.

Alternative Preconstruction Barriers. There is growing interest in finding alternative ways to do pretreats. Physical barriers consisting of sand, basaltic rock, and stainless steel mesh continue to perform well in research trials conducted by universities and the U.S. Forest Service. These physical barriers are also proving successful as commercial installs in Australia and Hawaii. Nonetheless, the comparatively high cost, availability constraints, and installation logistics may doom each of these termite control alternatives to limited use in this country.

A more functional approach for PCOs may soon come in the form of pesticide-impregnated sheeting. At least two termiticide manufacturers, AgrEvo and Zeneca, have publicly announced their plans to develop and hopefully market such a product in the not-too-distant future. AgrEvo is planning to develop a similar product here that they are currently selling for preconstruction treatments in Australia. Dr. Mark Coffelt, AgrEvo’s business support manager, describes the product (Kordon TMB) as a multi-layered sheet consisting of orange polyethylene on top, black polyethylene on the bottom, and a synthetic fibrous web impregnated with deltamethrin in the middle. The current product comes in 164-foot long by 5-foot wide rolls, and is designed to function as both a termiticide and a moisture barrier (TMB). A continuous barrier is created by overlapping and taping the Kordon sheets with duct tape before pouring the concrete slab. Duct tape and cable ties are also used to seal around plumbing and service penetrations.

According to Coffelt, the product will have several advantages. Correctly installed, it will carry a 10-year warranty against subterranean termite reinfestation. Since the insecticide (deltamethrin) is bound in a dry state in the inner webbing of the plastic laminate, the risks to installers, building occupants, and the environment are negligible. In fact, in Australia, Kordon TMB is exempt from registration as a pesticide.

Zeneca Professional Products is also developing a sheet-like, preconstruction product (Impasse) impregnated with their own proprietary insecticide. According to Dr. Bill McClellan, Zeneca’s national technical manager, the product is expected to afford termite protection for up to 20 years or longer, while also serving as a barrier against moisture and radon. Human safety and environmental attributes of Impasse are expected to be similar to AgrEvo’s Kordon TMB. Field testing is in progress and first sales are expected in one to two years.

While both of these preconstruction technologies sound exciting, the cost — and who will be doing the installing — is unclear. Both manufacturers concur that reinspections will need to be performed by PCOs. Will this also be true of installations?

NEW REFERENCE MATERIALS. No review of the current technology would be complete without mentioning three in-depth references on termites published during the past two years. Each contains valuable information that will be useful in training employees, educating clients, reinforcing your credibility, and dealing with claims and litigation.

The first is a book entitled Termites: Biology and Pest Management, written by M.J. Pearce, formerly of the Natural Resources Institute in the United Kingdom. The 172-page book provides a general scientific introduction to termite biology, behavior, pest status and control from an international perspective. Available from CAB International, 198 Madison Avenue, New York, NY 10016-4314 (Tel: 212/726-6490).

Another valuable new addition is the NPCA Research Report on Subterranean Termites, written by Dr. Barbara Thorne (University of Maryland) and Dr. Brian Forschler (University of Georgia). The comprehensive, 51-page report contains a wealth of useful information on the biology and management of subterranean termites, and dispels many myths which have been rampant in the industry for years. Available from the National Pest Control Association, Inc., 1800 Oak Street, Dunn Loring VA 22027 (Tel:703/573-8330).

Dr. Michael Potter is a professor and urban extension entomologist at the University of Kentucky.