Methods for discouraging termites include the basaltic termite barrier and metal mesh barriers under foundations, baiting systems, removable baseboards, and resistant building materials

Grace, J Kenneth

Tamashiro, Minoru

Yates, Julian R. III

ScholarSpace at University of Hawai'i at Manoa

Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Charles W. Laughlin, Director and Dean, Cooperative Extension Service, CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.Cooperative Extension Service Household and Structural PestsApril 1999HSP-3New Technology for Managing theFormosan Subterranean TermiteThe Formosan subterranean termite, Coptotermesformosanus Shiraki, is Hawaii’s most economicallyimportant insect pest, causing about $100 million in dam-age each year. Its biology, aggressiveness, and hidden,unpredictable invasiveness make this insect difficult todetect and control. This publication describes some tech-niques for managing this pest that have been developedrecently as alternatives to pesticides. Alternatives areneeded because the soil termiticides currently alloweddo not last as long as the products used before 1988,which have been banned. Also, many people simply donot wish to use pesticides around the home and prefernon-chemical control methods. The alternative tech-niques include physical (particle) barriers, wire-meshbarriers, in-ground and aboveground baiting systems,removable building components, and construction ma-terials resistant or unsusceptible to termite damage.Increased urbanization in Hawaii has made researchon controlling structural pests as economically and en-vironmentally important as research on agricultural pests.The concept of integrated pest management that guidescurrent pest-control efforts places an emphasis on avoid-ing pesticide use when possible. The condition ofHawaii’s fragile ecosystems and particularly the islands’water resources are serious concerns to consider whenevaluating pesticide uses and their subsequent environ-mental and health impacts. Research on low-toxicity ter-mite control strategies has been done by CTAHR ento-mologists with the goal of minimizing pesticide use inHawaii, especially in urban areas, and some of thesemethods have been commercialized.Physical barriers: the basaltic termite barrierPhysical barriers are gaining popularity world-wide asmethods of preventing attacks on structures by subter-ranean termites (also called ground termites). Researchhas shown that ground termites have difficulty penetrat-ing layers of certain granular materials, depending onJulian R. Yates III, J. Kenneth Grace, and Minoru TamashiroDepartment of Entomologythe material’s physical size, smoothness, shape, weight,and hardness. Studies in Hawaii and elsewhere havefound that for various termite species, suitable materi-als include crushed basalt, granite, or quartz, silica sand,and even glass shards. Research at CTAHR involvingextensive laboratory and field tests found that crushed,screened basaltic gravel is suitable as a barrier to theFormosan subterranean termite. This material is mar-keted in Hawaii as the basaltic termite barrier (BTB)(Ameron Hawaii, Honolulu).The Hawaii studies used irregularly shaped particlesin sizes ranging from less than 1⁄10 inch to about 1⁄5 inch(0.2–4.8 mm). The laboratory technique used a glass tubewith about 11⁄2 inch of the test material sandwiched be-tween layers of agar. Termites were put in one end ofthe tube and allowed to bore through the agar to thematerial. It was found that the termites were unable topenetrate basaltic particles sized from 7⁄100 to 9⁄100 inch(1.7–2.4 mm), even when they had access to the mate-rial for as much as five years. For practical applications,a layer of basalt at least 4 inches (10 cm) thick is recom-mended.In 1989, BTB was accepted into the City and Countyof Honolulu Uniform Building Code as a more perma-nent alternative to chemical soil treatments in Hawaii.The barrier can be used as a fill before pouring a con-crete slab foundation, be placed around the perimeter ofan existing concrete slab, or can be placed beneath andaround foundation retaining walls during new construc-tion. It can also be used to fill voids in hollow-tile con-struction. Although the primary use of BTB is for newconstruction, other postconstruction uses are being de-veloped.HSP-3 New Technology for Managing the Formosan Subterranean Termite CTAHR — April 19992Particle barriers can be difficult to install in somesituations or without proper training. Problems may oc-cur where the soil is unstable or not fully compacted,when surfaces at the edges of the barrier are rough orirregular, or if there is no protection from mixing withthe adjacent soil material. In general, installation bytrained professionals is recommended. Installation de-tails are available from Ameron Hawaii.Physical barriers: metal meshA termite barrier consisting of a marine-grade 316 stain-less steel mesh was recently developed and patented inAustralia as Termi-Mesh™ (Termi-Mesh Australia Pty.Ltd.), and it is currently used in building constructionthere. This mesh has an aperture size of 0.66 x 0.45 mm,which is well below the 1.2 mm aperture size found toprevent passage of foraging Formosan subterranean ter-mites in Hawaii. Tests showed that various Australiantermite species, including Coptotermes acinaciformis(Froggatt), were unable to penetrate the mesh.Experiments with the Termi-Mesh barrier on Oahushowed it to be effective as a barrier against the For-mosan subterranean termite, provided that the mesh wasproperly installed and seamlessly bonded to other ele-ments of the construction, such as concrete blocks, sothat termites could not circumvent the barrier.Pre- and postconstruction applications of the Termi-Mesh system are numerous. The product can be installedbeneath concrete slabs, around plumbing and electricalconduits, to seal concrete cracks and cold joints, to pre-vent penetration through hollow-tile retaining walls, andas a “sock” or “boot” to protect wooden fence posts andutility poles.The Termi-Mesh system was accepted into Hawaii’sUniform Building Codes for all islands in 1995 as astand-alone pretreatment for new construction. Sincethen, approximately 180 new-home installations havebeen done, and numerous postconstruction retrofits havebeen made to homes that were infested by Formosansubterranean termites. Termi-Mesh Hawaii (Honolulu)provides a substantial repair warranty should termitesbreach this physical barrier.Termite baiting systemsBaits are an attractive method for control of insect peststhat are cryptic (hidden or secretive) and social, such asground termites. Bait systems use only a small amountof insecticide, and it needs to contact only a relativelysmall proportion of the foraging population, who thenproceed to distribute the toxicant to other colony mem-bers. Certified pest-control operators in Hawaii currentlyoffer baiting systems marketed as Exterra™, FirstLine™,and Sentricon™. The Sentricon systems were the first tobe made available, and because they are the only onesthat have been thoroughly evaluated by CTAHR entomolo-gists, they are described here. The two basic types of baitstations in current use are in-ground and aboveground.In-ground stations. The Sentricon™ TermiteColony Elimination System manufactured and distrib-uted by Dow AgroSciences LLC (Indianapolis, IN) hasbeen in commercial use since 1995. It uses monitoringstations, plastic cylinders about 8 inches long and 13⁄4inches in diameter, with side ports to permit termite en-try, placed in holes augured into the soil. Each cylinderhas a tamper-resistant cap and contains two small, re-movable pieces of wood for monitoring. The stationsare placed around the building at intervals less than 15–20 feet apart, as well as elsewhere on the property whereground termites might be expected to occur.When termites are found in a monitoring station,the wood in the station is replaced with Recruit II™,consisting of a plastic cylinder with small holes in thesides containing cellulose impregnated with 0.5% hexa-flumuron, a chitin synthesis inhibitor.Even after adding bait to cylinders at a site, moni-toring of termite activity at unbaited cylinders aroundthe potential termite foraging area is essential. This docu-ments bait efficacy without confounding factors, suchas avoidance of bait, or deterrence due to mortality atthe cylinder. The primary practical goal of bait applica-tions is suppression or removal of the termite popula-tion to a level where termite activity can no longer bedetected in baited and unbaited monitoring stations, bothin the structure to be protected and elsewhere in the im-mediate vicinity of the structure.Beginning in fall 1993, field studies were conductedwith a prototype Sentricon system around three repre-sentative structures in Hawaii, each of which had a his-tory of subterranean termite infestation and recurringproblems. They were a four-unit condominium build-ing on Kauai, a single-family home on Oahu, and a largecommercial building on Oahu. All of these buildingshad concrete-slab foundations and had previously beentreated with soil insecticides around the exterior perim-3HSP-3 New Technology for Managing the Formosan Subterranean Termite CTAHR — April 1999eter and through the slab at various locations. Basaltictermite barrier gravel (Ameron Hawaii) had also beeninstalled in a trench around the condominium building.However, construction defects such as stucco extend-ing into the ground, concrete and asphalt walkways abut-ting the buildings, and (in the case of the residential struc-ture) rocky hillside soil conditions had contributed tocontinuing termite problems. Using the method of mark,release, and recapture, the termite foraging populationsat the sites were estimated at 0.33 million (Kauai), 0.94million (Oahu home), and 5.35 million (Oahu building).Application of hexaflumuron baits eliminated all termiteactivity at these sites. Continued monitoring is very im-portant, though. Several years later, termites were againfound to be reinvading two of these locations, but usingbaits again elimated the infestation.Aboveground stations. The in-ground Sentriconbaiting system is marketed as a preventive method forsubterranean termites and a remedial control tool for ex-isting infestations in structures. One limitation of the latterapproach is the length of time it could take to mitigatean ongoing infestation in a building within a reasonableamount of time while termites locate the bait stations.Some pest-control professionals have provided estimatesof this time ranging from one month to more than a year.The aboveground Sentricon baiting system devel-oped by Dow AgroSciences has been under study byCTAHR entomologists since December 1995 in fieldtrials using two buildings with ongoing Formosan sub-terranean termite infestations: a 12-floor high-rise resi-dential condominium building, and a large single-storyUnited States Department of Agriculture (USDA) fruitfly rearing facility.Inspection of the high-rise complex identified anaerial infestation (no connection to the ground) affect-ing the roof and two units on the 12th floor. Using mark-release-recapture methods, the termite foraging popula-tion was estimated at 469,000. After application of 0.1%and 0.5% hexaflumuron in two plastic bait stations at-tached to the roofing membrane, the infestation waseliminated in 76 days, as evidenced by lack of termiteactivity in monitoring stations containing untreated woodwafers as a food source and when the roofing membranewas replaced approximately two months later.Ground infestations affected several locations at theUSDA facility. Bait stations containing 0.1% and 0.5%hexaflumuron were attached to walls in the infestedrooms of the building, and modified in-ground Sentriconstations were installed around a detached infested stor-age container. Infestations in two of the building’s roomswere eliminated in 72 days, but termites remained ac-tive in monitoring stations located in another room, andaround the storage container and the building perimeter,indicating that multiple subterranean termite colonieswere infesting the site. Application of baits to stationsaround the storage container eliminated termites in allof these locations.Interest in developing aboveground bait systemsstemmed from the need to reduce or eliminate traditionalpesticide spot treatments within residential structures,as well as the possibility that the aboveground systemwould be a complement to or substitute for in-groundbait stations. Moreover, applying the bait to existinginfestations rather than waiting for termites to locatein-ground stations offers an expedient means of elimi-nating infestations within structures. The abovegroundsystem has been commercially available in Hawaii sinceearly 1997.Removable baseboardsTermite inspections of double-wall constructed build-ings (containing finished interior walls) have longtroubled the pest-control industry, sometimes resultingin litigation when termites are not detected either dur-ing an ongoing preventive pest-control inspection con-tract or when a home is inspected before its resale.A removable baseboard product was recently devel-oped by a Hawaii company (P.I.M. Development, Inc.,Kaneohe, Hawaii). It provides a nondestructive means toinspect sill plates, wall studs, and plumbing penetrationsthat are ordinarily concealed within double-wall voids.The prototype consisted of a spring-steel clip and spacerblock to attach a 31⁄4-inch, medium-density fiberboard tothe bottom edge of inner gypsum walls of double-wallconstructed homes. During construction, gypsum wall-board is secured to wall studs leaving 3 inches of spaceabove the finished floor. The clipped baseboard is attachedto the bottom edge of the gypsum wall. For existinghomes, the gypsum wall has to be cut 3 inches above thefinished floor to install the system as a retrofit. The pro-totype was not simple to install because its fitting andinstallation required special carpentry tools and skills andwas labor intensive. Continued product development ledto the current all-polymer Snap On Baseboards™ withHSP-3 New Technology for Managing the Formosan Subterranean Termite CTAHR — April 19994baseboards extruded from solid polyvinyl chloride andclips inject-molded with acetyl plastic that snap intogrooves molded in the back of the baseboard. A snap-incorner system was also developed to eliminate the needto miter baseboards to fit corners. Interest in the systemis growing in Hawaii and the mainland USA, where it isavailable from the manufacturer and hardware stores.Resistant building materialsThe use of steel framing in residential building construc-tion has increased in Hawaii in the past several years.However, the higher cost of steel and the need for spe-cialized installation procedures still limit its use. Froman environmental standpoint, the energy costs associ-ated with steel production and the production of preser-vative-treated wood products are also of concern.Naturally durable woods are a good alternative formany construction uses. For example, Western red ce-dar (Thuja plicata), Alaska cedar (Chamaecyparis noot-katensis), redwood (Sequoia sempervirens), and teak(Tectona grandis) have moderate to high resistance toFormosan subterranean termite attack. Although woodfrom the neem tree, Azadirachta indica, is not suffi-ciently resistant to termites to be useful in construction,both the wood and bark are less preferred by termitescompared to other tree species, suggesting that neemmight be useful for landscape plantings.A recent survey of indigenous and introduced Ha-waiian tree species found that sugi (Cryptomeria japon-ica), kou (Cordia subcordata), kamani (Calophylluminophyllum), milo (Thespesia populnea), and tallow-wood (Eucalyptus microcorys) were quite resistant toFormosan subterranean termite feeding. The currentavailability and wood characteristics of these speciessuggest that sugi, tallowwood, and milo may have thegreatest potential of the termite-resistant species in Ha-waii for expanded cultivation, harvest, and developmentand marketing of wood products.Conclusion“Urban entomology” is a new science that focuses onneeds of homeowners in rural as well as urban commu-nities. One role of the urban entomologist is to aid ac-ceptance of new technologies for control of insect pestsby educating homeowners, residential developers, ar-chitects, the construction industry, and pest control op-erators. Not all of these parties have the same ideas andmotives about new pest-control or pest-avoiding tech-nologies, which can add to construction costs. Develop-ers can be sales-oriented. Architects may follow aestheticcriteria in their designs that result in conditions condu-cive for urban pests. Some pest-control practitioners maybelieve that non-chemical pest control methods are aneconomic threat to their livelihood. Finally, homeownersmay perceive traditional chemical applications as morecost-effective in a short-term period.Proper construction techniques, such as isolatingwood from the soil, and the use of physical barriers toexclude subterranean termites, are practical approachesto preventing termite attack on structures. All too fre-quently, construction details that are conducive to ter-mite infiltration or to moisture accumulation and fungaldecay are incorporated into new buildings under theguise of economy or aesthetics. Certainly, adoption ofvigilant construction methods and the use of inert physi-cal barriers such as properly sized gravel to prevent ter-mite penetration into the structure promises more per-manent termite control than is possible with insecticideapplications to the soil alone. The new technologies canbe safer to use and potentially less harmful to the envi-ronment than relying only on pesticides. New solutionsto the problem of preventing and controlling infestationsby urban pests can be less costly in the long term.A list of references from the technical literature describing research on ter-mites and termite control methods can be obtained from the author by writ-ing to the Department of Entomology, 3050 Maile Way, Honolulu, HI 96822.Mention of a trade, company, or proprietary name does not constitute an endorsement, guarantee, or warranty by the University of HawaiiCooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitable products or companies.Caution: pesticide use is governed by state and federal regulations. Read the pesticide label to be sure that the intended use is included on it, andfollow all label directions.This and other recent CTAHR publications can be viewed on the college Web site, <www.ctahr.hawaii.edu/publications>,

New Technology for Managing the Formosan Subterranean Termite

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New Technology for Managing the Formosan Subterranean Termite

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