AUSTRALIAN CASE STUDY
Agricultural & Veterinary Chemicals Policy Section
Department of Primary Industries & Energy, GPO Box 858
Canberra ACT 2601
Australia
For the IFCS Meeting on POPs, 17-19 June, 1996- Manila, Philippines
Click to download: Elimination of Organochlorine Termiticides: Alternative Strategies for Controlling Termites in Australia, UNEP, June 1996, 28K/36K, English
(Note: the term organochlorine in this paper refers to cyclodiene termiticides).
Australia has a wide range of termite species, with a variety of preferred habitats and diets. There are a limited number of termites which are significant economic pests, causing damage to buildings and other structures. The majority of these species are subterranean termites, forming nests and tunnels under the ground.
Control of termites involves either preventative or curative means. The preference is for a preventative method of management, which generally involves the formation of a barrier between the soil, and therefore the termites, and the structural timbers. Barriers can be either of a physical or a chemical nature.
Traditionally chemical barriers involved the use of organochlorine chemicals, as they were relatively cheap and provided long term protection.
Australia has phased out the use of cyclodiene organochlorine termiticides from all jurisdictions except for chlordane in the Northern Territory where alternatives are not yet proven. However, Australia expects to have organochlorines phased out from use in the building industry by July 1997. The process of eliminating these chemicals has presented a number of challenges.
Differences in climatic conditions, soil types, termite species and building practices between different regions have led to difficulties in developing appropriate alternative treatments. Research into treatments which have suitable persistence, low mammalian toxicity and minimal environmental effects is still proceeding.
Phasing out these chemicals has required a flexible approach, with control regimes varying according to the circumstances. The experience in Australia has been that no single alternative is able to be employed to replace older control measures in all circumstances.
Australian termite fauna is rich, being represented by nearly 200 species. All areas of the continent are colonized by termites, although the species present may vary from region to region. Termites can be divided into three main categories based on behavioural characteristics. Although many termite species are grass feeders, the Australian region is well represented by groups that feed on timber and wood. Timber feeders can be divided into three main categories -subterranean termites, dampwood termites and drywood termites. The main timber pest species are contained in the subterranean termite group.
Dampwood termites attack dead and deteriorating trees, tree Stumps, poles in the ground and offcuts of timber left in the ground. They tend not to form a large central colony and to have their galleries, which are not extensive, in the soft growth rings of the tree.
Drywood termites live in many small independent groups, rather than forming a central colony. They are able to infest and destroy structural timbers, and one of these termites, Cryptotermes brevis is extremely destructive. This species has only been present in Australia since the early 1960's.
Subterranean termites include a number of species which form tunnels in the ground, ranging up to 100 m from the colony. The tunnels can extend under obstacles such as paths and concrete slab foundations. As the tunnels are kept sealed to preserve humidity, care is taken by the termites to ensure that wood surfaces attacked are not penetrated, and damage may therefore be very difficult to detect.
Termites do damage to trees in forests and plantations by degrading the wood and also damage ornamental trees and shrubs, but the most prominent economic damage occurs to timber in buildings and structures.
Mastotermes darwiniensis, the largest termite found in Australia, is found in areas of northern Australia. It is a very destructive species, attacking houses and other buildings, bridges, posts and poles and other plant and animal products. It also ringbarks and kills living trees, and damages crops such as sugarcane. In addition, it has been recorded as feeding on or damaging paper, leather, hides, wool, horn, vegetable fibre, hay, sugar, flour, bagged salt, bitumen, rubber, ebonite, human and animal excrement, and plastic or lead-sheathed cables. It is also able to corrode the surfaces of glass and some metals.
Termites of the genus Coptotermes are found in virtually all areas of Australia, and are responsible for the majority of economic damage to structures, although a number of other species may be extremely active locally.
Changes to building design can reduce the chance of termite infestation. Some strategies include:
Different building designs also present different problems and different approaches to control. Suspended flooring structures provide opportunities for inspection and relatively easy treatment, whereas concrete slab-on-ground makes inspection and retreatment difficult and places an emphasis on an initial treatment providing the longest term protection as possible. Sewerage, draining and electrical wiring offer points of entry for termites while cavity walls, mud brick structures and hollow brick construction provide concealed means of access.
Control techniques for termites can basically be divided into two categories, curative or preventative.
Many local building authorities require that preventative measures against termites are incorporated during the construction of a new building. As most termite related economic damage to timber in service occurs from sub-terranean termites preventative measures have relied heavily on the establishment of barriers aimed at preventing access to the premises/timber from the underlying soil. Barriers currently in use can be either chemical or physical. There has been some early research on the use of biological control agents as barrier control, however, this is still at an experimental stage. Barriers using biological control agents are unlikely to provide long term protection in all areas of Australia due to high temperature and humidity.
Curative techniques are options available if termite infestation is suspected in an existing structure. These measures can be put together into an integrated termite management approach, involving the use of regular inspections to try to detect the activity of termites, destruction of termites within the structure, and measures to locate and destroy the termite nest if early activity is detected. This may also involve other management practices, such as ensuring good subfloor ventilation which discourages termite activity and not allowing timber to be stacked against or near the house.
PREVENTATIVE MANAGEMENT: CHEMICAL BARRIERS
Organochlorine Termiticides
Historically, the organochlorine insecticides aldrin, dieldrin, chlordane and heptachlor constituted the major means of providing protection against subterranean termites. These have been used as chemical barriers and also in direct applications to manage termite infestation.
These chemicals were economical, effective and provided long term protection. It has been Australia's policy to phase-out and remove these chemicals where alternatives were proven to be effective. Aldrin, dieldrin and heptachlor are no longer used to control termites in Australia. Chlordane is restricted to use in the Northern Territory where alternatives are not yet considered to be proven effective for local situations and conditions. It is proposed to phase out the use of chlordane by mid-1997.
The persistence of the organochlorine insecticides has made them highly suited for use as chemical barriers to protect buildings against termite attack. Under ideal conditions they could theoretically provide building protection for 20-30 years or longer. These features also made them highly suitable for use under concrete slab constructions where retreatment was not possible without considerable disruption to the building and its occupants.
Chlorpyrifos
Chlorpyrifos has been registered for a number of years for the prevention of termite attack under suspended floors where retreatment is possible and also for use as a perimeter spray. In 1994 was approval given for the use of chlorpyrifos treatment under concrete slab-on-ground construction. This was initially via a reticulation system installed prior to the laying of the concrete to allow retreatment. In 1995 the direct hand spraying of chlorpyrifos for treatment under concrete slab-on-ground was approved.
There are concerns over the length of protection which may be achieved using chlorpyrifos on alkaline soils, due to concern that alkaline hydrolysis of chlorpyrifos would result in only a transient protection period.
Chlorpyrifos must be used at increased dose rates in tropical regions of Australia. With this rate, the expected life of the barrier is 6 years in northern Australia, in comparison to 10 years in southern regions. An external barrier applied around the house has an expected life of 3 years and 6 years respectively.
In approving the use of chloropyrifos there were significant concerns raised regarding the increased occupational health risks of using more acutely toxic chemical by hand spray and at times in confined spaces.
Bifenthrin
Bifenthrin is a synthetic pyrethroid that has recently been registered for use against termites. Currently, it is only approved for pre-construction treatment by hand spray. The application rate in northern Australia is 1.5 times the rate for southern Australia.
Other Chemicals
A number of other chemicals have been trialed in Australia. These include isofenphos and prothiophos, as well as alpha cypermethrin and esfenvalerate. Other synthetic pyrethroids and organophosphates have also been trailed. The companies have not proceeded from trial work to commercial development for a number of reasons including a lack of efficacy under some Australian conditions or a lack of commercial viability.
Trials are proceeding on other chemicals. At this stage these are not yet ready for commercial release.
Novel methods of administration are also being investigated. These include the incorporation of chemical into a fibrous blanket, which can then be applied as a sheet under the concrete slab. This decreases the occupational and public health and safety risk, as the chemical is incorporated under carefully controlled conditions in a manufacturing plant. Slow release formulations are also being investigated.
Trials using Metarhizium conidia as a repellent have been carried out. The conidia are mixed with soil to repel termites and prevent damage to susceptible timber. Conidia gave protection of up to 3 years in cool, dry conditions, but only protection of 6 months in tropical conditions. Tests are continuing to develop a method to provide protection to houses using the repellency effect. In a programme to evaluation application to houses, good control was achieved for over one year in most cases.
Nematodes are the only other biological control means which appear to be effective against Australian termites. They are only effective against larger termite species, and do not appear to have a repellency effect at this stage.
Biological control methods therefore show some potential as barrier treatments. Further work on efficacy and evaluation of possible public and occupational health and safety issues is required.
Granite chips
Work has been performed in Hawaii utilising a physical barrier using basalt chips, a similar technique using granite was developed in Australia.
This consists of an inert barrier of granite particles of a specific size. The effective particle size varies with the size of the target species of termite. The particles must be too large or heavy for the termites to move, with the spaces between particles too small for termites to pass through. The granite chip treatment is only available for new buildings below the Tropic of Capricorn, as Mastotermes darwiniensis can move particles of a size which will exclude Coptotermes spp., and the small termite species also found in northern Australia can pass through the barrier. Research is proceeding on a barrier system which will simultaneously exclude Coptotermes spp, Mastotermes spp and other species.
The availability of material of the correct size is important as transport costs become a limiting factor where there are long distances from quarry sites. The technique is not generally applicable to established buildings.
Stainless steel mesh
This technique involves the installation of a layer of fine mesh of stainless steel under the building.
The most common has an aperture size of 0.66 mm x 0.45 mm, using wire strands with a diameter of 0.18 mm. For concrete slab construction, the mesh can be used to cover the complete subfloor. Alternatively, the mesh can be partially installed to protect service openings and into wall cavities, in combination with a concrete slab construction that minimises the formation of cracks and voids.
Tests carried out indicate that mesh of diameter 0.6 mm x 0.6 mm provided adequate protection against Coptotermes acinaciformis in both laboratory and field trials. There was no evidence of damage to the mesh by the termites, although there was evidence of termite activity on and around the mesh. In later trials mesh of 0.66mm x 0.45mm was used as this was the mesh size proposed for use. This also gave adequate protection against C. acinaciformis and Mastotermes darwiniensis. The timber was not, however, protected against Heterotermes vagus, which, with a maximum head width of 0.76 mm, was able to pass through the apertures. A mesh size of 0.4 mm x 0.4 mm was required to give adequate protection against H vagus.
This technique is not yet proven in northern Australian conditions where building techniques commonly require structural tie-rods which penetrate the concrete and enter the soil for anchorage of the superstructure against cyclone damage. These rods provide a potential path of entry for termites. The other difficulty encountered in northern Australia is the problem of the distances between population centres. The need for properly trained personnel to install the mesh would present difficulties in the Northern Territory, where it has proven necessary to train a number of builders in the application of pesticides to allow work on buildings to proceed. These builders are only licensed to apply chemicals where the construction site is a distance greater than 100 kilometres (60 miles) from a major post office.
Arsenic Dusting
The use of arsenic dusting to control termite infestations presents difficulties as the dust is toxic and has variable effectiveness. It is necessary for there to be large numbers of termites and an expert operator in order for this treatment to be effective. It is difficult to determine if control has been achieved as termite tend to vacate galleries if disturbed.
Mirex
Mirex is currently approved as a toxicant in baits to protect trees in northern Australia, where Mastotermes darwiniensis is a problem. This use is still approved, as there has not been a suitable alternative developed, despite extensive research. The termite causes significant damage to growing trees in orchards. A number of other chemicals have been trialed, including soil treatments with organophosphates and synthetic pyrethroids. The application rates to soil required to achieve control using these chemicals are such that unacceptable residues were detected in the produce.
Because of the direct application of the chemical, less than 10 kg of mirex are used annually in Australia. The technique is primarily aimed at the control of infestations to growing trees.
Biological Treatment of Existing Infestations
There are no biological control products currently registered for the treatment of buildings infested with termites. Research by the Commonwealth Scientific & Industrial Research Organisation (CSIRO) is developing a number of biological pesticides with activity against termites.
Most research has involved the use of nematodes and fungi, as there are few pathogenic termite viruses or protozoa, and the only bacteria reported to kill termites in the laboratory do not appear to be effective in the field. Nematodes have the disadvantage that only large termite species are particularly susceptible to infection. A number of fungi have been shown to be effective against termites in the laboratory. Several of these are unsuitable for use as biological control agents as they are also opportunistic pathogens of humans and other animals. Others are not effective at the temperatures found in a termite nest, or are of too low a virulence to be useful. A strain of Metarhizium has been isolated which possesses many useful characteristics.
Most effective control is achieved when large numbers of pure, dry Metarhizium conidia are blown directly into the nursery region of the colony. If smaller regions of the colony are infected,the region is walled off and the colony as a whole survives. The CSIRO, however, have concluded that classical biological control of termites is not possible.
Other chemicals
In general, using other chemicals, such as permethrin, depend on discovering the nest and treating it directly. Many termite species which are successful in the urban environment do not generally build nests.
Monitoring and Bait Stations
The use of a monitoring station with an attractive food, such as decaying wood or paper refuse, will allow the presence of termites to be detected. The termite species can be determined, and treatment options developed. The station can then be treated with a chemical such as arsenic trioxide, which may result in the destruction of termites in the nest. Eradication cannot be guaranteed and secondary attacks can result in significant damage before it is discovered due to the concealed nature of the termite activity. This is only possible where the dwelling has some open ground surrounding it - in extremely built up areas this is not an option
COSTS ASSOCIATED WITH ALTERNATIVES
One of the major advantages of using the organochlorine termiticides was their relatively low cost, seen both in a lower cost of initial treatment and also in the longer activity of the chemicals requiring infrequent retreatment. As part of a study on the use of organochlorine insecticides for termite control an estimate of the costs associated with a variety of termite control measures was made (Table 1).
PUBLIC AND OCCUPATIONAL HEALTH AND SAFETY CONCERNS
The replacement of cyclodiene termiticides (some of the so-called 'organochlorines') with alternative chemical barriers is not without occupational and public health risks. The toxicity of alternatives including the organophosphates (OPs), bifenthrin and hexaflumuron are briefly outlined below. On the basis of the high acute toxicity of the OPs and the fact that required treatments of houses by pest-control operators (PCOs) need to be much more frequent than with the cyclodienes formerly used, suggest that there is a greater risk of poisoning events, involving both PCOs and possibly householders and/or their pets.
The use of new technologies which include a monitoring and baiting system to chemically kill termite colonies promises to dramatically reduce the potential exposure of PCOs and householders to termiticides.
Organochlorines
The cyclodiene termiticides provided highly-effective, low-cost chemical termite barriers, with no clearly recognisable adverse human health effects at the levels of exposure arising from their properly approved use. However, because of their environmental persistence, metabolic stability, lipid solubility and resultant bioaccumulation, there remains the possibility of biologically adverse effects after their accumulation to high levels.
Chlorpyrifos
Chlorpyrifos is available in Australia and is registered for use as a termiticide. It is a quite toxic member of the OP class of chemicals (oral LD50 in rats reported to be in the range 96 to 300 mg/kg bw), capable of acute cholinergic poisoning typical of the cholinesterase inhibitors. In Australia, 'Dursban Pre-Construction' termiticide can only be used by trained licensed pest-control operators.
Chlorpyrifos is relatively non-volatile (comparable to heptachlor and chlordane) but is reported to have a mild mercaptan odour which can be noticeable after treatment of dwellings.
Apart from their potential to cause acute poisoning because of their inhibition of cholinesterases, concerns about the OP class of pesticides, including chlorpyrifos, relate to their potential for chronic effects (ie. effects after repeated exposure), even if one-off exposures are small. These include their possible visual system toxicity, their neurobehavioural toxicity and their delayed peripheral neuropathic effects.
Their potential for ocular toxicity was first raised by a range of Japanese studies in the 1970's which involved investigations of people living near agricultural areas extensively sprayed with OPs. More recently, long-term studies in rats have revealed a range of toxic and pathological effects on the visual system for at least some OPs.
Whilst original experimental data did not indicate that chlorpyrifos had the potential to cause OPIDN (organophosphate-induced delayed neuropathy) in tests in hens, several recent reports (eg. Kaplan JG et al. Neurol 43 2193-2196: 1993) indicated that it could cause reversible, sensory neuropathy in humans. However, a recent re-investigation in neurotoxicity screening studies in Fischer rats did not reveal any evidence of sensory neuropathy after acute or 1 3-week exposures (Mattson JL et al. Fd Chem Tox 34, 393-405:1996).
Of concern with OPs is their potential to cause neuropsychological effects, viz. changes in brain function, after long-term exposure (eg. Stephens R. et al. The Lancet 345, 1135-1139:1995). Acetylcholine is a neurotransmitter in the brain and it is reasonable to suspect that inhibition of acetylcholine metabolism in the brain could have subtle effects on behaviour and cognition. However, such effects are difficult to predict from conventional toxicity tests using animals and even more difficult to study in humans.
Recently, a report has been published suggesting a possible association between 'Dursban' exposure and multiple birth defects in 4 cases (Sherman JD, Arch Env Hlth 51(1), 5-8: 1996).
Other organophosphates
Other organophosphates considered as possible termiticides include isofenphos and prothiofos.
Isofenphos is available in Australia but is not registered for use as a termiticide. It is a highly toxic member of the OP class of chemicals, capable of acute cholinergic poisoning typical of the cholinesterase inhibitors (oral LD50 in rats reported to be in the range 20 to 48 mg/kg bw) Studies for teratogenic effects and for neurotoxicity (delayed effects) appear to have been equivocal.
Prothiofos is much less acutely toxic than isofenphos (oral LD50 in rats reported to be in the range 1000 to 2000 mg/kg bw) but signs and symptoms of poisoning would be expected to be similar to other members of the class. There appears to be limited data on this chemical but available developmental and delayed neurotoxicity studies appear to be negative for toxic effects.
Synthetic Pyrethroids
Bifenthrin
Pyrethroids are divided into two types (I and II) on the basis of differences in signs of neurotoxicity - the Tremor (T) and Choreoathetosis-Salivation (CS) syndromes. Pyrethroids can cause morphological changes in peripheral nerves of rats when given in doses near the LD50. These (reversible) morphological changes are probably a secondary consequence of the primary action of pyrethroids, which is on sodium channels. Paraesthesia can be a local reversible and short-lived effect of some (mainly Type II) pyrethroids. There is no evidence for other neurotoxic effects. Since the action on sodium channels is reversible and esterase systems rapidly detoxify pyrethroids, it is difficult to achieve systemic poisoning when absorption is slow, ie. by skin or oral routes. Thus pyrethroids generally have a good safety record.
However, bifenthrin (Type I pyrethroid) has been reported as being very stable in the environment and hardly metabolised in plants or animals. Its acute toxicity is high (worst oral LD50 in mice and rats in the range 40 to 53 mg/kg bw). Tremors are commonly observed in repeat-dose studies (rats, rabbits, dogs). A statistically significant increase in non-malignant tumours of the urinary bladder in male mice at high dietary doses has been reported although the compound was not genotoxic; the US EPA classified bifenthrin as a Class C (possible human) oncogen. It was without teratogenic or delayed neurotoxic effects.
Other pyrethroids
Fenvalerate and permethrin are other possible termiticides; fenvalerate is registered as a termiticide in the USA for soil treatment in and around homes. Permethrin is also registered as a termiticide in the USA for use by PCOs. Preparations of this pyrethroid are used in human therapeutic preparations as headlice treatments.
Permethrin (type I pyrethroid) is stable to light and heat, but disappears rapidly from the environment.
It is hag moderate to low acute oral toxicity, depending on the vehicle (worst oral LD50 in rats, 430 mg/kg bw in corn oil, 1725 mg/kg in water). In repeat-dose studies in animals, permethrin was without carcinogenic, reproductive, teratogenic or mutagenic effects but muscle tremors and liver toxicity were noted. Neurotoxic effects were seen in various animal species, generally at high doses.
It can induce paraesthesia in exposed humans - numbness, itching, tingling and burning are symptoms frequently reported.
Fenvalerate (type II pyrethroid) is stable to light, heat and moisture. In water and on soil surfaces, fenvalerate is degraded by sunlight; in general, environmental degradation is rapid and leads to less toxic products. Fenvalerate does not accumulate in adipose tissue and there is no appreciable bioaccumulation of it or its metabolites.
Fenvalerate has moderate-to-high acute oral toxicity (worst oral LD50 in rats is 245 mg/kg, dissolved in corn oil). In repeat-dose studies there was no evidence of mutagenicity, reproductive toxicity or teratogenicity. Signs of neurotoxicity have been seen in dogs (at 6.25 mg/kg/d) and morphological evidence of myelin disruption in sciatic nerves of rats (reversible) has been reported. In mice, microgranulomatous changes have been observed in liver, lymph nodes and spleen (with a NOEL of 1.7 mg/kg/d).
Occupational exposure to fenvalerate has been associated with abnormal facial sensations developing between 30 min and 3 h after exposure and lasting for 30 min to 8 h.
POSSIBLE FUTURE CHEMICAL ALTERNATIVES
Hexaflumuron
Hexaflumuron is a benzoylurea compound which is active as a chitin synthesis inhibitor.
Consistent with other members of this class of insect growth regulators, hexaflumuron has very low acute toxicity (oral LD50 greater than 5000 mg/kg in rats). It is not teratogenic, carcinogenic or mutagenic, and does not induce delayed neurotoxicity in hens. However, in a range of repeat-dose studies in mice, rats and dogs, it produced significant increases in methaemoglobin levels, with a resultant increase in haematopoiesis in some cases.
DowElanco are developing this compound as part of a system to detect termites, eliminate colonies and provide protection against re-infestation. The method involves placing small 'stations' (approx. 6 inches in diameter and flush with the ground, resembling a lawn sprinkler) in the ground around the house (30 for a typical house). Initially, pieces of wood are placed in the stations and if there are signs of termite activity, then hexaflumuron is applied in baits in the same stations
Studies by CSIRO in Australia have unambiguously demonstrated the elimination of field colonies of Coptotermes acinaciformis and Nasutitermes exitiosus after foragers fed on bait matrix treated with hexaflumuron.
One drawback to the widespread introduction of this system would be the need to monitor 30 or more stations on a reasonably regular basis.
The organochlorine termiticides have long been recognised as a cause for environmental concern because of their persistent properties and tendency to bioaccumulate in wildlife. These concerns led to the phaseout of their remaining termiticide uses (except in the Northern Territory where the deadline extends to 30 June 1997 in recognition of the more severe termite problems in that part of Australia).
Impacts on wildlife from the use of persistent organochlorines have been evident in recent years. Mortalities of tawny frogmouths (an owl species) have been observed in springtime, apparently because food is scarce and birds mobilise their fat reserves, thereby releasing accumulated organochlorine contaminants. Sydney's north shore has been a hot spot. The contamination appears to arise from use of organochlorine termiticides, although the precise pathway is unclear. Such incidents were not reported during spring 1995, perhaps because these chemicals had been recently phased out, although a return to more normal weather conditions after prolonged drought in eastern Australia may also have contributed to improved owl health.
Chlorpyrifos is widely used in Australian agriculture and home gardens. Additional use as a termiticidal barrier beneath dwellings does not represent a significant increase in environmental exposure relative to existing uses.
Chlorpyrifos has raised environmental concerns in Australia. For example, a major incident was reported in early 1995 at an ibis rookery in the Macquarie Marshes (central New South Wales) involving mortality of many nestlings. The incident appeared to be linked to the organophosphate insecticide chlorpyrifos. Although the source of contamination was not discovered, and could have been many kilometres from the rookery, termiticide uses are not suspected.
Bifenthrin is registered for use in Australian cotton. Although its very high aquatic toxicity is noted, no incidents have been reported from agricultural use. Bifenthrin is a typical synthetic pyrethroid in sorbing very strongly to soil with little potential for movement. These properties make bifenthrin well suited from the environmental perspective for use as a termiticidal soil barrier beneath buildings.
For both mirex (used as a bait) and arsenic (used for dusting), quantities involved are small as the grooming habits of termites spread the toxicant through the colony until the queen is exposed and dies.
While Australia expects to have organochlorines phased out from use in the building industry by July 1997, the process of eliminating these chemicals has presented a number of challenges.
Differences in climatic conditions, soil types, termite species and building practices between different regions have led to difficulties in developing treatments which are appropriate. Further research into treatments, to develop treatments with a suitable persistence and lower mammalian toxicities are proceeding.
There has been a need to ensure a flexible approach and that control regimes will need to vary with the circumstances to hand. Experience has shown that no single alternative is able to be employed to replace older control measures in all circumstances.
Table I Comparative costs associated with various termite control measures
Control Method Building under Retreatment Comment
construction
(170-200m2)
Integrated Termite $200-$300 (but may Variable up to $500 Annual inspections
Management vary depending on necessary and may
Approach building involve destruction
(involving a range modification) of nest
of control
measures)
Organochlorine $237-$496 $200-$1500 Regular inspection
advised. Annual
retreatments are
often done
unnecessarily, may
only be necessary
every 5 or 10 years
Chlorpyrifos $480-$715 $290-$2150 Regular inspection
advised. More
frequent
retreatments may be
necessary compared
to Organochlorines
Stainless Steel
Mesh Barrier
Partial treatment $500-$800 Not Required Inspection of
(perimeter and building for
entry points) termite activity
still required
Full Slab Underlay $3000-$4000 Not Required
Crushed Stone $800-$1000 Not Required Inspection of
Barrier building for
termite activity
still required
Source: National Registration Authority for Agricultural & Veterinary Chemicals, Inquiry into the Use of the Organochlorine Insecticides for Termite Control, 20 January 1994.