Termite Control: Changing Attitudes and Technologies

J.P. La Page

Department of Entomology, Louisiana State University Agricultural Experiment Station, LSU Agricultural Center, Baton Rouge, Louisiana, 70803, USA

ABSTRACT

Termites accountfor nearly $2 billion per annum in losses to structures throughout the world. After nearly 40 years, chlorinated hydrocarbon termiticides are being replaced with less persistent and presumably safer soil pesticides. Changing attitudes are providing a foundation for experimentation and eventual implementation of alternative control strategies involving wood preservatives, baiting systems, biological control, and physical methods.

INTRODUCTION

Wood is one of our most valuable construction materials. While it possesses many favourable attributes including strength, widespread availability, natural beauty, and renewability, it is compromised by at least one serious deficiency. When not properly protected or when lacking natural durability, it is biodegradable. Despite a substantial body of knowledge of wood preservation, about one third of the world's timber production is lost annually to various agents of biodegradation (Edwards & Mill 1986). Although about 2200 species of termites (lsoptera) are known worldwide, with most restricted to the tropics, they figure prominently among the causal agents of wood destruction.

ECONOMIC IMPORTANCE

While termites are most generally recognized for their attacks upon structures, their proclivity for destroying cellulosic materials is not

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limited to timbers in buildings. Utility poles and railway sleepers are attacked throughout the tropics. In Louisiana (USA), even creosoted electric transmission poles are regularly attacked by the Formosan subterranean termite, Coptotermes formosanus Shiraki. Other items damaged include paper products, boats and ships, underground cables, agricultural crops, pasture grasses, and live trees in forests, orchards and urban areas. In New Orleans, Louisiana, and other coastal cities in the USA, C. formosanus is a serious pest in marine pilings treated with creosote.

Credible information on the economic losses by termites is difficult to obtain and virtually lacking for anything but damage to structures. Mauldin (1982) reported annual losses in the United States of $750 million resulting from prevention, remedial control and repair. About 95% of the loss is attributed to subterranean termites (Reticulitermes, Heterotermes, Coptotermes spp.). Based upon reports from the pest-control industry, set costs of termite treatments worldwide are $1·92 billion for 1985. However, not all termites are destructive. The vast majority of species actually serve a critical role in nutrient cycling in tropical and temperate ecosystems.

TERMITE CONTROL-PAST AND PRESENT

The remainder of this paper will focus on control procedures for subterranean termites. An excellent review of control methods for drywood termites is given by Edwards & Mill (1986).

Prior to World War II, subterranean termite control consisted largely of creosote or pentachlorophenol impregnations for wood and experimental soil treatments with pitch, tar, creosote, arsenic salts, orthodichlorobenzene, trichlorobenzene, and chlorinated naphthalenes. Many of these compounds were objectionable because of health hazards, odour, or phytotoxicity. In 1939, a laboratory was established by the USDA at Gulfport, Mississippi, dedicated to the study of termite problems. Long-term soil-treatment tests were installed there during 1943. The cyclodiene pesticides, discovered at about this time, were first incorporated into the testing programme with the inclusion of chlordane in 1948. In 1949, the related compounds, dieldrin and aldrin were included and heptachlor in 1952. Now known as the Forestry Sciences Laboratory, this group remains very active in the testing of candidate pesticides for soil treatments in the United States.

The four cyclodiene soil termiticides demonstrated exceptional efficacy providing 100% effectiveness in ground-board studies for at least 34 years.

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With nearly 5 years of field efficacy, chlordane was marketed for use as a soil termiticide in 1952. Although several other compounds including lindane (gamma-HCH) and DDT, have been registered for soil treatment, none has achieved so widespread acceptance as the four cyclodienes. In addition to persistence in soil, they have been relatively inexpensive, widely available, and, until recently, considered safe.

In 1978, concern about possible health hazards led the US Environmental Protection Agency (EPA) to cancel all uses of chlordane except for subterranean termite control. A paper by Livingston & Jones (1981) which reported contamination ofliving spaces by chlordane was the first indication that the cyclodienes were in trouble. Subsequent reports on television, radio, and in the press eventually led to the banning of chlordane in New York and Massachusetts during 1984-85. Dieldrin and aldrin were removed from the market voluntarily by manufacturers. Even greater pressure to ban cyclodienes is apparent now as a subcommittee of the US House of Representatives considers an amendment to the federal Clean Air Act which would ban chlordane in the United States on the basis of potential health hazards. Saudi Arabia was the first country to ban cyclodienes for termite control (in 1984) and Japan has eliminated the use of these compounds.

As concerns over pesticide safety have increased, so has acceptance of more expensive and less persistent termiticides. In 1980, the organo­phosphate, chlorpyriphos, was registered as a soil termiticide and another Isofenphos, in 1982. More recently, a pyrethroid, permethrin, has become available for use in soil treatments. Several additional compounds are effective for termite control but are not yet registered or marketed. These include endosulfan, bromocyclen, fenvalerate, a particularly promising compound, cypermethrin and severat others.

Nearly all termiticides today are applied as soil treatments. Nevertheless, concerns about human health and environmental contamination continue to mount. Nearly 500 million kg of pesticides are applied to c. 148 million hectares annually. While the total amount applied to agricultural lands far exceeds that in urban areas, the rate of application in or under structures is much higher than on farmland or forests. Chlordane is currently applied at a rate of 390 kg/h under and adjacent to buildings (La Fage, 1986). Data such as these have prompted discussion and initiation of research on alternative termite-control strategies.

FUTURE TRENDS IN TERMITE CONTROL

Future methods for subterranean termite control will likely fall into four

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categories: (1) pesticides in wood, (2) baiting systems, (3) biological control, and (4) physical methods (Edwards & Mill, 1986).

Pesticides in wood

Many wood preservatives are currently used to protect structural timbers against decay. Some of these, including CCA, ACAs, AACs, dimethylol compounds and borates, are also effective against termites (Williams & Amburgey, 1987). However, termites can crawl over treated products to reach unprotected wood. Among the organophosphorus insecticides, chlorpyriphos is effective as a wood preservative for protection against termites and is being marketed in a number of countries. Several pyrethroids also protect against termites when used as wood preservatives. Although the possibility of using natural wood extractives or their synthetic analogues has been widely researched (Carter & Beal, 1982), no commercial products have been developed to date. Research has also been conducted on the resistance to termite attack of wood impregnated with plastic resins and polyethylene glycol (De Groot & Esenther, 1982). Other studies have produced termite repellents and antifeedants (Scheffrahn & Rust, 1983).

Baiting systems

In the bait-block method of subterranean termite control, wooden baits impregnated with a slow-acting, non-repellent toxicant are placed in the foraging territory of termite colonies. Termites feed on them and return the toxicant to the central nest where it is shared with nestmates via trophallactic exchanges and grooming. The entire colony may be destroyed within a few weeks. Dechlorane (mirex), has been used effectively as a bait toxicant in the USA, Australia and China. Although the use of this insecticide has been banned by the EPA, no suitable alternative has yet been discovered. A number of insect growth regulators including methoprene (Jones, 1987) and fenoxycarb show promise in laboratory studies. The future of these compounds will not be known until field trials, now underway, are completed. Other toxicants that have been tested include the fluorolipids, chitin synthesis inhibitors and the protozoacide, chlortetracycline.

Biological control

In late 1983 the nematode, Neoaplectana carpocapsae F., was introduced in the USA as a biological control for subterranean termites. Subsequent

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research at Gulfport, failed to establish the efficacy of this organism and recent reports (Mix, 1986) have largely discounted its future use.

Among the fungi which attack termites, several species in the genera Metarhizium and Beauveria appear to have some potential as control agents for subterranean termites. Studies in Hawaii (Lai et al., 1982) and Australia (Hanel & Watson, 1983) yielded inconclusive but promising results.

Physical control

Little research has been conducted on physical methods of controlling subterranean termites. Ebeling & Pence (1957) evaluated substrate particle size as a deterrent to substrate penetration by Reticulitermes hesperus (Banks). More recently, Tamashiro et al. (1987) demonstrated in laboratory trials that C.formosanus is incapable of tunnelling through a substrate containing basaltic particles 1·7-2·4 mm in diameter.

CONCLUSION

In many countries, the era of subterranean termite control with cyclodiene soil insecticides is nearing an end. Many new soil termiticides have been introduced and more will probably follow. Looking further into the future, it is likely that alternative control strategies, especially baiting systems, will be perfected and ultimately accepted by the pest­control industry and consumer.

REFERENCES

Carter, F.L. & Beal, RH. (1982). International Journal of Wood Preservation, 2, 185-91.

De Groot, RC. & Esenther, G.R (1982). In Structural Use of Wood in Adverse Environments, ed. R.W. Meyer & RM. Kellogg. Van Nostrand Reinhold, New York, pp. 219-45.

Ebeling, W. & Pence, R.J. (1957). Journal of Economic Entomology, 50, 690-2. Edwards, R & Mill, A.E. (1986). Termites in Buildings. Rentokil Ltd, Felcourt East

Grinstead, W. Sussex, 261 pp. Hanel, H. & Watson, JA.L. (1983). Bulletin of Entomological Research, 73,

305-13. Jones, S.c. (1987). Effects of methoprene on Coptotermes formosanus (Isoptera:

Rhinotermitidae). International Research Group on Wood Preservation, IRG/WP/1322.

726 J.P. La Fage . La Fage, J.P. (1986). In Proceedings of the National Conference on Urban

Entomology, ed. P A Zungoli. 24-27 February, 1986, College Park, MD, University of Maryland, pp.45-57.

Lai, P-Y., Tamashiro, M. & Fujii, J. (1982). Journal of Invertebrate Pathology, 39, 1-5.

Livingston, J.M. & Jones, C.R. (1981). Bulletin of Environmental Contamination and Toxicology, 27,406-11.

Mauldin, J.K (1982). In Biology of Social Insects, ed. M.D. Breed, C.D. Michener & H.E. Evans. Proc. 9th Congress Int. Union Study Social Insects. Westview Press, Boulder, CO, pp.138-41.

Mix, J. (1986). Pest Control, 54, 48, 54. Scheffrahn, R.H. & Rust, M.K (1983). Journal of Chemical Ecology, 9, 39-55. Tamashiro, M., Yates, J.R. & Ebesu, R.H. (1987). The Formosan subterranean

termite in Hawaii. Proceedings of a symposium on The Biology, Ecology, and Control of the Formosan Subtemmean Termite, 25 June, 1985, Pacific Branch of the Entomological Society of America, Honolulu, HI (in press).

Williams, L.H. & Amburgey, T.L. (1987). Forest Products Journal, 37, 10-17.

An extended bibliography for this paper may be obtained from the author.