1 Novel Technologies for Subterranean Termite Control

Transcription

1 1 Novel Technologies for Subterranean Termite Control by Nan-Yao Su 1 ABSTRACT When building repair cost is included, the economic impacts of termites may reach up to $11 billion annually the United States. The dollar amount spent on termite control will continue to grow as the living standard in developing countries is improved and more termite pest species are transported by human commerce. Currently-registered soil termiticides include chlorpyrifos, permethrin, cypermethrin, bifenthrin, fevalerate, imidacloprid, and fipronil. Physical barriers such as stainless-steel mesh and soil particle barriers are also available but have yet to see widespread use; while insecticide-impregnated polymer barriers may become available in the near future. Aside from these barrier techniques, population control using baits have become more widely adopted by the industry in recent years. Baits containing hexaflumuron, sulfluramid, or diflubenzuron are currently available for the pest control industry. As evidenced from these developments, future technologies need to conform to efficacy and environmental standards. It is no longer satisfactory to rely merely on barriers for structural protection from subterranean termites, and future control measures need to address structure protection through population management of subterranean termites (i.e., baits). It will probably become less acceptable to spray a large quantity of insecticide in soil to protect a house from subterranean termites, and future technologies need to use less pesticide (i.e., baits), no pesticide at all (i.e., physical barriers), or controlled-release pesticide barriers (i.e., insecticideimpregnated polymer). Keywords: Soil termiticide barrier, physical barriers, insecticideimpregnated polymer barrier, baits INTRODUCTION Based on sales figures for liquid termiticides and the expense ratio of termiticide cost in relation to the termite control cost, the total annual amount spent by the consumers for subterranean termite control was estimated at $1.5 billion in the United States in 1993 (Su 1994). A similar estimate in 1999 resulted in a $2.2 billion cost; a ca. 50% 1 Ft. Lauderdale Research and Education Center, University of Florida, 3205 College Ave. Ft. Lauderdale, FL 33314

2 2 Sociobiology Vol. 39, No. 3, 2002 increases in 6 years. These figures did not include the repair cost of damaged buildings. A limited survey in the City of New Orleans suggested a 4:1 ratio for repair vs. control cost for the Formosan subterranean termite, Coptotermes formosanus Shiraki (E. Bordes, New Orleans Mosquito and Termite Control Board, personal communication). If this ratio is adopted, the total annual economic impact of subterranean termites in the United States could amount to $11 billion in Because the termite control market in the United States is generally considered to account for 50% share of the worldwide market, the global economic impact by subterranean termites may reach $22 billion annually. It should be noted, however, that the repair/control cost ratio varies depending on termite species and living standard among regions, and thus the figure presents only a rough estimate. Although a reliable figure is difficult to formulate to accurately assess the global economic impact of termites, it is certain that economic loss due to termites will continue to increase. One factor contributing to such increase is the improved living standard in developing countries. In areas such as United States and Japan, a single termite species (C. formosanus) can sustain a multimillion dollar termite control industry because the housing and repair cost easily surpass the control costs (Su and Scheffrahn 1998), but despite the abundance of destructive termite species, an organized service industry providing termite control has been scarce throughout much of the tropics and subtropics. As the living standards improve in the subtropics and tropics where termites are abundant, the control cost become more affordable, and the economic impacts in these areas will certainly increase when more is spent to protect houses from termites. One such example is illustrated by the increased spending on termite control in Malaysia in recent years (Lee 2001). The propensity of increasing urban population in these countries will further exacerbate the problem. Movement of termite pests by commerce is another factor contributing to the increase of economic impacts by termite worldwide. A matured colony of drywood termites can survive in a small piece of wood without free water and can be easily transported from place to place. The West Indies powerpost termite, Cryptotermes brevis (Walker), for example, is found in 11 of the 16 regions as categorized by Edwards & Mill (1986) (Table 1). Subterranean termite species that require constant moisture are less likely to survive transportation than drywood species, but two Coptotermes species, C. formosanus and C. havilandi Holmgren, have been transported to more than 5 regions of the tropics, subtropics (C. havilandi) and temperate areas (C. formosanus) (Table 1). As evidenced by C. formosanus in the United States, exotic termite

3 Su, N.-Y. Novel Technologies for Subterranean Termite Control 3 Table 1. Termite pest species found in multiple regions (of the 16 regions as divided by Edwards and Mill 1986) Species Regions found Cryptotermes brevis 11 Drywood termite Cr. dudleyi 6 Cr. domesticus 4 Cr. havilandi 4 Coptotermes formosanus 6 Subterranean termite Co. havilandi 5 Reticulitermes lucifugus 4 R. flavipes 3 pests can cause devastating damage. In areas where the native species do not cause substantial damage, the discovery of exotic termite pest species is usually treated as a curiosity until a widespread problem develops. Because of the lack of damaging subterranean termite species in Chile in the past, for example, no serious efforts were taken to control the Reticulitermes sp. (most likely R. santonensis Feytaud) when it was found in Santiago in the mid-1980s. Currently this Reticulitermes sp. is causing substantial damage to housings throughout Santiago and has been found in other areas such as Quillota and Valparaiso (Ripa and Smith 2000). As more termite species are transported by human commerce, similar incidents will probably occur more frequently. Subterranean Termite Control Options Currently there are two major approaches, barrier techniques and population control to protect structures from subterranean termites. Barrier treatments. The objective of a barrier technique is to exclude soilborne termites from structures. Traditionally, liquid insecticides have been applied in soil beneath and/or surrounding a structure to create a barrier. One organophosphate (chlorpyrifos) and four pyrethroids (permethrin, cypermethrin, bifenthrin and fevalerate) are currently registered as soil termiticides. The acute toxicity of chlorpyrifos and repellency of pyrethroids prevent termite tunneling into treated soil (Su and Scheffrahn 1990). Non-repellent termiticides such as imidacloprid and fipronil are registered for soil treatment in recent years. These are suggested to kill termites when they tunnel through the treated soil, but there are no published data to date to demonstrate their impact on field populations of subterranean termite colonies. Soil termiticide treatments are in use since the early 1900s, and are generally less expensive, readily available and acceptable to the pest control industry. In many regions, soil treatment is installed during

4 4 Sociobiology Vol. 39, No. 3, 2002 building construction as required the building codes or real estate lenders. Liquid insecticides are also popular for remedial treatments because of potential immediate effects, but the home owners dislike the disruptive procedures such as drilling of foundation floors. Due to its intangible nature, it is also often difficult to verify the proper rate of termiticide application. Another disadvantage of conventional liquid termiticide application is the large quantity of insecticide use. When used in a 1% solution, the soil application of termiticide could reach ca. 390 kg per hectare which exceeds the pesticide application rate of ca kg per hectare in agricultural lands (La Fage 1986). Unlike the persistent cyclodienes that were withdrawn from the industry in the mid-1980s, current termiticides degraded more rapidly, and reapplication of these soil termiticides are needed for continuous protection of structures. Recently, under the agreement between the US Environmental Protection Agency and manufacturers, sales of chlorpyrifos as soil termiticides will be severely limited within a few years. As with cyclodienes and chlorpyrifos, the scrutiny over the potential environmental hazards of current soil termiticides will continue. Mirroring the safety concerns of soil termiticide barriers, two physical barrier types, uniform sized particles and stainless steel screening, have been employed as non-chemical controls in recent years. When used as continuous horizontal barriers installed during pre-construction installation, these physical barriers withstood intensive foraging activities of several termite species under field conditions (Tamashiro et al. 1987, Smith & Rust 1990, Su et al. 1991, Su & Scheffrahn 1992, Lenz & Runko 1994, Grace et al. 1996, Lewis et al. 1996). These non-chemical barriers are semipermanent and can be readily installed during construction. Their tangible nature also provides ease for verification by regulatory inspectors. They are used most effectively as continuous horizontal barriers for new structures installed during construction, and their role in the future of subterranean termite control may depend on their acceptance by the construction industry and willingness of buyers to absorb the cost. Another recent development of novel barriers is the insecticideimpregnated polymer barriers. Polymer films are often placed between subslab soil and concrete foundation to prevent moisture permeation from soil into the structure. When impregnated with repellents such as pyrethroids, the treated polymers function both as the termite barrier and moisture barrier (Su, unpublished data). Because the insecticide is confined in a polymeric matrix, there are less environmental concerns than application of soil termiticide, and better yet, termiticide longevity is controllable by alternating the polymer characteristics. This tangible

5 Su, N.-Y. Novel Technologies for Subterranean Termite Control 5 product can be adopted as a built-in procedure during construction. Due to their novelty, however, there could be installation challenges that may appear when they are field tested on a large scale. It is also unknown if and how the building or pest control industry may embrace this technology. Population control. The objective of a population control technique is to impact (eliminate or suppress) termite populations near structures. Currently, baits containing hexaflumuron, diflubenzuron, or sulfluramid are registered for population control of subterranean termites, but there are differences in efficacy and claims among these products. Numerous studies have demonstrated the elimination of all detectable subterranean termite activity by hexaflumuron baits at a variety of locations with a variety of different termite species, to the point where citations to the published literature are superfluous (Grace & Su 2001). Consequently, baits containing hexaflumuron are marketed as a monitoring-baiting system that does not require additional pesticide use, while sulfluramid baits are recommended for use in conjunction with other treatment methods such as liquid termiticides (Potter 1997). For the monitoring-baiting system using hexaflumuron, baits are not used until termites are detected in the monitoring stations and hexaflumuron is distributed by termites; resulting in a small quantity of hexaflumuron (ca. 1g) needed for eliminating a colony of subterranean termite (Su 1994). Bait stations are tangible, and a continuous protection of structures is achieved for as long as the monitoring program is in place. Because the in-ground stations are usually installed in outdoor soil, there is little need to drill or alter the structures. The monitoring-baiting program, however, requires frequent visits by the technicians who need to be knowledgeable on termite biology. Another disadvantage of baiting is the lengthy time it may take to achieve control. Future Trends in Subterranean Termite Control Novel technologies developed in recent years for subterranean termite control include physical barriers, insecticide-impregnated polymer barriers, non-repellent termiticides, and monitoring-baiting programs for population control. As evidenced from these developments, future technologies need to conform to efficacy and environmental standards. It is no longer satisfactory to rely merely on barriers for structural protection from subterranean termites. Future control measures need to address structure protection through population management of subterranean termites (i.e., baits). It will probably become

6 6 Sociobiology Vol. 39, No. 3, 2002 less acceptable to spray 500-1,000 liters of insecticide in soil to protect a house from subterranean termites. Future technologies need to use less pesticide (i.e., baits) or no pesticide at all (i.e., physical barriers). If a pesticide is to be used, it needs to be used in a controllable manner such as the insecticide-impregnated polymer barriers. ACKNOWLEDGMENTS The author thanks R. H. Scheffrahn and W. Kern (University of Florida) for review of the manuscript. This article is Florida Agricultural Experiment Station Journal Series No. R REFERENCES Edwards, R. & A. E. Mill Termites in Buildings. Their Biology and Control. Rentokil Limited. W. Sussex, UK, pp Grace, J. K. & N.-Y. Su Evidence supporting the use of termite baiting systems for long-term structural protection. Sociobiology 37: Grace, J. K., J. R.Yates, C. H. M. Tome, & R. J. Oshiro Termite-resistant construction: use of a stainless steel mesh to exclude Coptotermes formosanus (Isoptera: Rhinotermitidae). Sociobiology 28: La Fage, J. P Subterranean termites: A personal perspective. Proc. Nat l. Conf. Urban Entomol. College Park, MD, 24-27, February 1986, p Lee, C.-Y Subterranean termite pests and their control in the urban environment in Malaysia. Sociobiology 37: (in press) Lenz, M. & S. Runko, S Protection of buildings, other structures and materials in ground contact from attack by subterranean termites (Isoptera) with a physical barrier - a fine mesh of high grade stainless steel. Sociobiology 24: Lewis, V. R., M. I. Haverty, D. S. Carver, & C. Fouche Field comparison of sand or insecticide barriers for control of Reticulitermes spp. (Isoptera: Rhinotermitidae) infestation in homes in northern California. Sociobiology 28: Potter, M. F Termite baits: a status report. Pest Control Technology 25: Ripa, R. & J. Smith Termites as structural pests in Chile. Pp 42-43, In: IOMC, Report of the UNEP/FAO/Global IPM Facility Termite Biology and Management Workshop. UNEP Chemicals, Geneva, Switzerland. Smith, J. L. & M. K. Rust Tunneling response and mortality of the western subterranean termite, Reticulitermes hesperus (Isoptera: Rhinotermitidae) to soil treated with insecticides. J. Econ. Entomol. 83: Su, N.-Y Field evaluation of a hexaflumuron bait for population suppression of subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 87:

7 Su, N.-Y. Novel Technologies for Subterranean Termite Control 7 Su, N.-Y. & R. H. Scheffrahn Comparison of eleven soil termiticides against the Formosan and eastern subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 83: Su, N.-Y. & R. H. Scheffrahn Penetration of sized-particle barriers by field populations of subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 85: Su, N.-Y. & R. H. Scheffrahn A review of subterranean termite control practices and prospects for integrated pest management programs. Integrated Pest Management Reviews 3: Su, N.-Y., R. H. Scheffrahn, & P. M. Ban Uniform size particle barrier: a physical exclusion device against subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 84: Tamashiro, M., J. R. Yates, & R. H. Ebesu The Formosan subterranean termite in Hawaii: problem and control. pp In: M. Tamashiro and N.-Y. Su [eds.], Biology and control of the Formosan subterranean termite. College of Trop. Agr. Human Resources, Univ. of Hawaii, Honolulu, HI.