Technological Needs for Sustainable Termite Management

229 Technological Needs for Sustainable Termite Management by Nan-Yao Su1 ABSTRACT Sustainability of current termite control practices was examined from three perspectives: economic, social and environmental. Soil termiticide treatments, which account for >80% of current subterranean termite control practices in the United States, provide more inancial incentives (economic) for the industry than bait treatments, which account for <20% of the market share. While more expensive to operate, bait systems can be used to manage termite populations in a community (social) with less toxic insecticides at smaller quantities (environmental) than soil termiticide treatments. Because the labor expense associated with quarterly site visits for current bait systems is the main reason for the cost diference between soil termiticides and bait systems, there is a need to develop technologies to reduce the frequency of on-site inspections. Electronic sensing and automated monitoring devices have been developed, but the equipment cost prohibits the widespread use of such technologies. A durable bait that protects active ingredient (AI) and bait matrix from degradation is a promising technology that may reduce the annual service frequency to a level comparable to that of soil termiticide treatments so that the "socially" and "environmentally" more sustainable bait technology will become as "economically" sustainable as the soil termiticide treatment. Keywords: soil termiticide, termite bait, subterranean termite IPM, durable bait SUSTAINABILITY Sustainability generally implies “the ability to maintain the balance of a certain state in a system,” but its meaning difers depending on the context in which it is being used. In the broad scale of “human sustainability,” it was deined by the Brundtland Commission in 1983 as “… (to meet) the needs of 1 Department of Entomology and Nematology, Ft. Lauderdale Research and Education Center, University of Florida, Ft. Lauderdale, FL 33314. Email: [email protected] 230 Sociobiology Vol. 58, No. 1, 2011 the present without compromising the ability of future generations to meet their own needs.” (World Commission on Environment and Development 1987). Although oten criticized as too vague to be useful, this deinition nonetheless ofers a foundation for formulating the frameworks of sustainability at various scales, including economic sectors, countries, municipalities, home gardens, individual lives, occupations, and others. (Anonymous 2005). hree pillars of sustainability - economic, social and environmental - are considered elements of sustainability, although they are not equally weighted (Porritt 2006). he economy is a subset of the society which is a subset of the environment. hus the environmental sustainability encompasses the social dimension in which lies the economic sustainability. his, however, does not diminish the importance of economic sustainability. In the free market system, commercial activities that are not economically sustainable will not survive to be considered for their social or environmental impacts. his paper examines the sustainability of a very small subset of human activities, the termite control industry in the United States. CURRENT TERMITE CONTROL PRACTICES here are generally two approaches to subterranean termite control: soil applications of liquid termiticides to create a chemical barrier and termite baits for managing the populations of subterranean termites in the vicinity of a structure. Soil treatments have been widely used by commercial termite control irms for subterranean termite control since the early 1900s. Initially, it was assumed they “eradicated” subterranean termites from the soil, but such treatments were later found to serve only as foraging barriers between sources of infestations and the structures to be protected (Randall & Doody 1934). Insecticides used for ground treatments during the 1930-1950’s included sodium arsenite, trichlorobenzene, DDT, pentachlorophenol, creosote, and ethylene dibromide (USDA 1951), followed by the widespread use of cyclodienes, such as chlordane, heptachlor, aldrin, and dieldrin, until the mid-1980s when they were cancelled for use in termite control. Organophosphates (OPs) and pyrethroids soon replaced cyclodienes, but soil termiticides containing chlorpyrifos (an OP) were phased out by 2006, based on an agreement in 2000 between registrants and the USEPA. Current soil treatments include either non-repellent Su, N.-Y. — Technological Needs for Sustainable Termite Management 231 termiticides (ipronil, imidacloprid, chlorfenapyr, chlorantraniliprole) or repellent pyrethroids (bifenthrin, cypermethrin, and permethrin). he irst bait product using a chitin synthesis inhibitor (hexalumuron) was commercialized in 1995. Numerous ield studies demonstrated that ield colonies of subterranean termites could be eliminated by chitin synthesis inhibitors, such as hexalumuron, due to their dose-independent lethal time (Su 2003a). Following the irst commercial bait product, however, other baits using metabolic inhibitors, such as sulluramid, were also commercialized. Lethal time of a metabolic inhibitor is dose-dependent, and thus usually cannot eliminate the large subterranean colonies (Su & Schefrahn 1998). Consequently, baits containing metabolic inhibitors have to be used in conjunction with a soil termiticide. Currently, there are several bait products using novilumuron, hexalumuron, dilubenzuron, or sulluramid as the active ingredients (AIs). A 2002 survey of termite control industry in the United States showed that 77% of termite control irms used liquid termiticides (48% for non-repellent termiticides, and 29% for repellent termiticides) and 38% used termite bait products (Anonymous 2002). As of 2008, liquid termiticides probably accounted for >80% (>50% for nonrepellent, and <30% for repellent), while baits accounted for <20% of the market for subterranean termite control. A subterranean termite colony may contain 100,000 to more than 1,000,000 individuals with a foraging territory extending up to 100 m (Su & Schefrahn 1988, Grace et al. 1989, Su et al. 1993). Despite the application of a large quantity of insecticide, soil termiticide barriers usually do not afect the majority of subterranean termite populations around structures (Su & Schefrahn 1988). Early on, it was speculated that non-repellent termiticides might impact subterranean termite populations (Kard 2001, horne & Breisch 2001, Potter and Hillery 2002, Wagner 2003, Hu 2005, Ibrahim et al. 2003), but recent laboratory (Su 2005, Rust & Saran 2006) and ield studies (Osbrink et al. 2005, Ripa et al. 2007) showed that, due to their dose-dependent lethal time, these non-repellent termiticides function primarily as barriers, without any substantial impact to the subterranean termite populations in the vicinity of treated houses. he surviving colony(s) or portions of colonies not afected by termiticide barriers may move on to infest nearby structures and produce alates that further infest other areas. It was recognized that the target unit 232 Sociobiology Vol. 58, No. 1, 2011 of control for subterranean termites has to be a termite “colony” instead of a termite “individual,” and the primary goal of a termite bait system was to eliminate a colony (Su 1994). Field studies with baits showed that typically a few grams of hexalumuron were needed to eliminate a colony of subterranean termites (Su 1994, Su 2003a), and on average the rate of 0.065 kg per hectare is required (and probably less for novilumuron currently being marketed in the United States) for successful control. When used properly, bait applications eliminate whole colonies of subterranean termites and thus reduce termite damage potential in treated areas. INTEGRATED PEST MANAGEMENT (IPM) FOR SUBTERRANEAN TERMITES In formulating the conceptual framework of IPM for subterranean termites, Su and Schefrahn (1998) recognized that it was unrealistic to directly apply the cost-beneit model developed for agriculture IPM to urban pest management program. here are vast diferences in perception of damage potential and in tolerance threshold between these two environments. Instead, Su and Schefrahn (1998) focused on the same underlying concept of IPM to use a cost-efective approach to solve the pest problem, and considered it vital to include the costs of potential risks associated with pesticide application on human health and the environment. Because the long-term outcome of pesticide application is unpredictable, it was suggested that less toxic and less persistent pesticides should be used in smaller quantities to ensure environmental sustainability. Instead of merely excluding termites from a house, the needs of managing the termite population were stressed so as to address the sustainability at the community level. Under this framework, two criteria are required for termite IPM, namely 1) reduction of termite damage potential through population management, and 2) minimizing the negative environmental impact by using less persistent, less toxic insecticides at a smaller quantity (Su & Schefrahn 1998). Baiting systems, especially those with chitin synthesis inhibitors, use a minute amount of insecticide to eliminate colonies of subterranean termites, thus satisfying the requirements of population management with reduced pesticide reliance. In comparison Su, N.-Y. — Technological Needs for Sustainable Termite Management 233 with liquid termiticides that are used by >80% of the termite control industry, it is apparent that baits are more suitable tools for termite IPM. SUSTAINABILITY AND CURRENT TERMITE CONTROL PRACTICES Economic concerns he business model for Table 1. Comparison between soil termiticide and termite bait the termite control indus- usage in the United States and their environmental impact. try has been to protect the Liquid termiticide Bait structures under contract rate (A) 39,000 65 with individual homeown- Application (g/hectare) ers. Most homeowners who Oral LD50 (B) 97* >3,160** pay the treatment costs are (rat, mg/kg) 402.06 0.0206 not familiar with control Relative Impact (A/B) options and their pros and Labor cost Initial installation (h) 2-4 1 cons, and typically depend Annual service once quarterly on pest control professionMarket share (%) >80 <20 als to decide the control *ipronil, **novilumuron methods. he primary goal of a pest control irm is to generate proits, and the economic concerns dominate the three pillars of sustainability. he major diference in the cost structure between soil termiticides and bait treatments is the labor expense. Time required for the initial installations are 2-4 h and 1 h per house for soil termiticides and bait treatments, respectively (Table 1). he follow-up service for soil termiticide treatment typically constitutes one site visit annually, while the current monitoring-baiting program requires a technician to visit the site four times per year to inspect and maintain the bait system. hus, ater the initial year, the bait system becomes more costly for a pest control irm to operate and they pass on the cost to the homeowners. his explains the >80% market share of liquid termiticide usage in the United States. he lower cost of liquid termiticide applications is shared by both termite control industry and the homeowners, making the business model based on liquid termiticides more proitable and economically sustainable. 234 Sociobiology Vol. 58, No. 1, 2011 Social concerns When applied properly, liquid termiticides can protect a home from soilborn termites, but their inability to eliminate a subterranean termite colony allows the surviving populations to continue to infest nearby structures. For invasive species such as the Formosan subterranean termite, Coptotermes formosanus Shiraki, the industry’s reliance on liquid termiticides is probably the main reason for the establishment and spread of C. formosanus from four isolated port cities in the 1960s to the entire southeastern United States by 2000s (Su 2003b). Another invasive termite pest, the Asian subterranean termite, C. gestroi (Wasmann), was discovered in Miami, FL in 1996 (Su et al. 1997) and has since been found from Key West to Palm Beach County, FL (Schefrahn & Su 2000). Coptotermes gestroi is primarily found in the tropics and subtropics and is the most economically important pest species in Southeast Asia, Brazil and the West Indies. Because soil termiticides remain the tool of choice for control of C. gestroi by the termite control industry, its potential to become a major termite pest species in the United States, especially in warmer regions, resembles that of C. formosanus in the early 1960s. he inability of soil termiticides to manage populations of subterranean termites at the community level and to prevent the spread of invasive species into other regions renders them unsuitable as the socially sustainable control option. Environmental concerns he fate of pesticides in the environment is diicult to predict once they are applied. Chlordane, for example, was cancelled for use in termite control in the mid-1980s, but a recent report indicated a strong correlation between termiticidal use of this cyclodiene in termite-infested areas and its concentration in whole ish sampled in 1992-2001 (Nowell et al. 2009). Its persistence in underwater sediments apparently still has an efect on wildlife 10-20 years ater being applied. he total amount of pesticides used for termite control in the urban sector is smaller than is used in agriculture. But it is also applied in a much smaller area of an urban environment that has frequent human traic, and its potential risk may be greater. La Fage (1986) was the irst to point out that the application rate of soil termiticide, 390 kg per hectare (based on 1% inal product for chlordane that dominated the soil termiticide market in Su, N.-Y. — Technological Needs for Sustainable Termite Management 235 the 1950s – 1980s), was ≈200-fold higher than the agricultural rate of 2.17 kg per hectare (Pimentel & Levitan 1986). Even with the current rate of 39 kg per hectare (based on 0.1% inal product for ipronil that is used by the majority of termite control industry), it is still 20-fold greater than the agricultural rate, and probably more, as the current agricultural rate is certainly less than the 2.17 kg per hectare estimated in 1986. he pesticide use rate for a monitoring-baiting system such as the Sentricon® system (Dow AgroSciences, Indianapolis, IN), on the other hand, is ≈0.065 kg per hectare (Table 1). he diference in application rate between soil termiticides and baiting systems is 600-fold. But the application rate alone does not represent the true impact of the insecticide use in termite control to the environment. Most soil termiticides are more toxic than the chitin synthesis inhibitors used in bait systems. he mammalian oral LD50 for ipronil, for example, is 97 mg/kg, while that for novilumuron exceeds 3,160 mg/kg (Table 1). When a “relative impact index” (RI) is deined as the quotient of application rate (A) and oral LD50 (B), or RI = A/B, RI values are 402.06 x 1000-3 and 0.0206 x 1000-3 (kg2/ mg*hectare) for ipronil and novilumuron, respectively. Based on the relative impact index, the environmental impact of soil treatments with ipronil is 19,517-fold greater than the bait systems using novilumuron. SUSTAINABLE TERMITE MANAGEMENT AND TECHNOLOGICAL NEEDS It is obvious that bait systems that use an AI with lower toxicity at a smaller quantity are more environmentally sustainable than soil termiticides. Bait systems are also more socially sustainable due to their ability to eliminate subterranean termite colonies, to manage populations of pest termite species over a large area, and to prevent the spread of invasive species to other regions. Labor costs associated with bait systems, however, provide less inancial incentives for the industry to embrace this technology. If bait systems are to be more widely adopted by the industry so that termite control practices are more “socially” and “environmentally” sustainable, the cost structure of operating bait systems has to be at least as competitive as that of soil termiticides. he key issue in the cost structure of baiting systems is the labor expenses associated with the current requirement of quarterly inspection and site visit (Table 1). here are two technologies that may reduce these labor expenses: 236 Sociobiology Vol. 58, No. 1, 2011 electronic monitoring and reduced frequency in monitoring by using durable baits. Electronic monitoring Su et al. (2000) developed a sensor painted with a conductive circuit that converts termite feeding activity into electric signals. he concept of using electronic sensors has been commercialized as the Sentricon® ESP (Electronic Sensing and Protection). With the Sentricon® ESP, a pest control technician no longer has to manually open the stations to visually inspect the contents, thus reducing the time required for a site visit. his technology can save substantial labor expenses, especially in large sites where many stations have to be monitored. he expenses for the equipment of a Sentricon® ESP system (sensor, interrogator, transponder, and wireless data recorder), however, are too costly for its use in sites with small numbers of stations. Consequently, it is used primarily by pest control irms with large commercial accounts. Although conceived as a solution to the labor costs associated with the monitoring process of the bait system, the added equipment expense, unfortunately, does not always justify the savings. When the electronic sensors are connected to an on-site datalogger that is accessible through communication means such as telephone lines, termite activities in a remote site can be monitored without the need of a site visit (Su 2002). he remote system can be easily automated to continuously monitor numerous sites without the need for frequent site visits. hus, the savings can be substantial. he expense of the remote monitoring system with datalogger, as described by Su (2002), however, is still too costly to be commercially viable. With the advance of developments in electronic technology, the equipment cost may be reduced enough in the future so that its use is inancially justiied. Reduced monitoring frequency with durable baits Another solution to the high labor cost due to quarterly site visits is to reduce monitoring frequency by using AI-containing baits that are protected from the elements (Su 2007). Cellulose-based matrices used in current commercial bait products degrade easily, especially in the warm and humid environment that is favored by subterranean termites. Consequently, baits containing AIs are applied only when termites are found in the stations dur- Su, N.-Y. — Technological Needs for Sustainable Termite Management 237 ing the monitoring phase. he current quarterly site visit is needed so as to avoid the total depletion of the monitoring devices and abandonment of the stations, especially for aggressive species. When cellulose baits were hermetically sealed within a closed-cell polyethylene sheet envelope and placed in soil, termites readily tunneled through the polyethylene sheet to consume the baits, resulting in colony eliminations (Su 2007). he polyethylene sheets were impervious to water and temperature luctuations and protected the cellulose baits and AI from the environment for at least one year. he sealed baits containing AIs may be placed in soil for extended periods without the need of frequent monitoring. A commercial version of such durable baits, Sentricon® HD (High Density), was recently registered with an annual inspection requirement. It is expected that the annual service frequency of such durable baits will be comparable with that of soil termiticide treatment so that the “socially” and “environmentally” more sustainable bait technology will become as “economically” sustainable as the soil termiticide treatment that currently accounts for >80% of the market share. 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