Table of Contents

Chapter: 3

III.   TERMITES AS STRUCTURAL PESTS

III.1 DETECTION AND IDENTIFICATION

III.2  DAMPWOOD TERMITES 

III.3  DRYWOOD TERMITES

III.4  SUBTERRANEAN TERMITES

III.5  ARBOREAL NESTERS

III.6  
TERMITE PESTS AND MANAGEMENT BY CONTINENT
AFRICA  
AMERICAS
ASIA
AUSTRALIA
EUROPE

III.7  ALTERNATIVES TO POPS

III.8  
TERMITE MANAGEMENT SYSTEMS
DESIGN OF A BUILDING
PRESERVATIVE-TREATED TIMBER PRODUCTS
PHYSICAL BARRIERS  
TERMITICIDE APPLICATIONS TO SOIL AND NON-SOIL SUBSTRATES  
BAITING SYSTEMS  
SPACE FUMIGATION  
THERMAL CONTROL  
BIOLOGICAL CONTROL

<<Chapter 2  -   Chapter 4>>

III.    Termites as Structural Pests
(INCLUSIVE OF DAMS, ROADS, UTILITY POLES, & UNDERGROUND CABLES AND PIPES)

            Termites become a problem when they damage structural timber and other materials in structures. Damage may extend to household furniture, paper products, many synthetic materials and food items.  Each year hundreds of thousands of structures (bridges, dams, decks, homes, retaining walls, roads, utility poles, and underground cables and pipes) require treatment for the management of termites.  Proper design of a building and building practices, installation of termite management systems at the time of construction and ongoing regular inspections for termite activity can greatly reduce the risk of termite damage to structures.

             Internationally important termite pests include species from subterranean, arboreal, dry and wet wood feeding ecologies. Important termite genera include Mastotermes Family-Mastotermitidae; Cryptotermes, Incisitermes, Kalotermes, Neotermes Family-Kalotermitidae; Coptotermes, Heterotermes, Psammotermes, Reticulitermes, Schedorhinotermes Family-Rhinotermitidae; Macrotermes, Microtermes, Nasutitermes, Odontotermes Family-Termitidae. Many regions of the world are experiencing expansions of termite activity and/or invasions by exotic termite species.

III.1   Detection and Identification

            Termite adults are sometimes confused with winged forms of ants.  The adult reproductive stages of both ants and termites leave their nests in large numbers to establish new colonies.  However, ants and termites can be distinguished by checking three features: antennae, wings, and abdomen (Fig. 1).  Signs of subterranean termite infestations include evidence of soil and tunnels and swarming of winged forms; drywood termite infestations are usually obvious by the presence of characteristic dry pellets in wood or on horizontal surfaces beneath infested wood.  Swarming of winged termites occurs seasonally and is highly variable depending on species and continent (see Basic Biology).  Darkening or blistering of wood in structures is another indication of an infestation; wood in damaged areas is typically thin and easily punctured with a knife or screwdriver.  Visual searches are the most frequent means for detecting termite infestations in structures.  More modern innovations for improving termite detection include odor detectors, feeding-sensitive devices (acoustic emission), fibre optics, microwave technology and infrared cameras..  However, some of these technologies are experimental, and most are expensive and have limited availability.  No detection technology is 100% effective in all circumstances.  Using a combination of different technologies for detecting the presence of termites is the best approach.

            Once a termite infestation has been located, if there is doubt as to the nature of the infestation, a specimen of infested wood material or the termite specimens themselves, preserved in a small amount of alcohol, can be sent to a specialist for diagnosis and identification.

            There are dozens products and techniques, chemical, nonchemical, and biological available to manage and prevent drywood termites. Many of the sections and tables in these web-pages are dedicated to helping the reader decide on which options to further explore.

 

III.2   Dampwood Termites

            Species in this ecological group are composed of two families of termites, Termopsidae and Kalotermitidae.  The common name “dampwood termite” is confusing because some species actually prefer drier wood.  The pest status for this group is minor compared to the other termite groups listed below.  If treatment is required the procedure includes local treatment with a chemical, infested wood removal, or prevention (use of chemically treated woods or keeping structural wood dry and away from sources of water and dampness).

 

III.3   Drywood Termites

            As was mentioned when using the common name “dampwood termite,” the same applies to the use of the common name “drywood termite.”  There is some variance in the ecology and biology of species in this group; however, for the most part, drywood termites infest dry, sound wood, including structural lumber, as well as dead limbs of native trees, shade and orchard trees, utility poles, posts, and lumber in storage. From these areas, winged reproductives seasonally migrate to nearby buildings and other structures, usually on sunny days during summer and/or fall. Drywood termites are most prevalent in many coastal and arid locations around the world.  Drywood termites have a low moisture requirement and can tolerate dry conditions for prolonged periods. They do not connect their nests to the soil. Piles of their faecal pellets, which are distinctive in appearance, may be a clue to their presence. The faecal pellets are elongate (a mm or less long) with rounded ends and have six flattened or roundly depressed surfaces separated by six longitudinal ridges (see Fig. 3).  They vary considerably, but appear granular like multi-colored sand. There are dozens products and techniques, chemical, nonchemical, and biological available to manage and prevent drywood termites.  Many of the sections and tables in these web-pages are dedicated to helping the reader decide on which options to further explore.

 

III.4   Subterranean Termites

            Subterranean termites require a source of moisture in their environment.  To satisfy this need, they usually nest in or near the soil and tend to reach their food sources from the underlying soil.  They maintain some connection with the soil through tunnels in wood or through shelter tubes that they construct (Fig. 2).  These shelter tubes are made of soil with bits of wood and termite faecal material.  Termites readily chew through a number of other materials including plasterboard (drywall) and plastics.  The most significant damage they cause occurs in foundation and structural support wood. Subterranean termites are very abundant in many parts of the world and sometimes have large colonies, often exceeding 1,000,000 individuals and foraging over a 10,000-m2 area. 

            Reproductive winged forms of subterranean termites, developing from wing-budded nymphs, vary in color from black to pale brown: their wings are opaque to gray to dark charcoal.  The time of swarming varies considerably among species, but usually occurs after rain (see Basic Biology).  Soldiers have more pronounced and pigmented heads. Their long, narrow heads have no eyes.  They have elongated mandibles or other defensive structures.  Some species of termites have no soldiers, but in most species soldiers comprise from 1 to 25% of the colony.  Workers (roughly 80% of the colony) are smaller than reproductives, wingless, and have a smaller head than soldiers. There are dozens products and techniques, chemical, nonchemical, and biological available to manage and prevent subterranean termites.  Many of the sections and tables in this website are dedicated to helping the reader decide on which options to further explore.

 

III.5   Arboreal Nesters

            Some arboreal nesting termites are important structural pests in tropical and subtropical America, from northern Argentina to Mexico, Asia, and Australia. One species has recently been introduced into Florida (USA).  They usually build carton nests on trees, poles, fences, and under the roof of old buildings. Some species build a single nest, but others build multiple, interconnected nests. These termites have nasute soldiers with a brown to black head and a conical "nose" through which they can squirt a defensive liquid. However, some arboreal species in Asia Microcerotermes do not have nasute soldiers. Workers are larger than soldiers. They usually damage wood that is moist and decayed, but sometimes they feed on sound wood, as well as paper. Problems usually occur when a nest is present on a tree near a building. They reach the building through carton tunnels, which are easily visible on the walls and structural wood. Sometimes the nest can be inside the building, under the roof or inside the walls. Arboreal nasute termites may reach a building not necessarily by tunneling through the soil, but via galleries built over the soil surface. By doing so they are even able to circumvent chemical soil barriers, however, because their presence is relatively easy to detect, direct nest treatment is often a management option. These termites are a serious problem in historical buildings in South America.

             Alates of several genera of subterranean termites (Coptotermes and Reticulitermes) are able to establish a colony in the upper parts of buildings, railway carriages and the like, without the need for contact with the soil, as long as they have a source of moisture (for example leaking roofs, gutters, and plumbing). These infestations can be treated effectively by fumigation and baiting.

 

III.6   Termite Pests and Management by Continent

Africa

The African continent is climatically and geographically diverse and contains the world's largest desert and also one of the highest mountain peaks.  Termite diversity reflects this topological and climatological diversity.  More than 1,000 of the > 2,600 recognized species are found on the African continent.  Mound-building species of termites occur throughout most of the African landscape.  Genera infesting wooden structures include Reticulitermes, Coptotermes, Psammotermes (Family Rhinotermitidae), Anacanthotermes (Hodotermitidae), and several species of Kalotermitidae.  However, there are additional species with agricultural impact (see Termites in Agroecosystems).  Some species of termites have been transported over much of Africa due to commerce and nomadic migration.  The tropical forests of central Africa and all of southern Africa also contain a diverse and abundant termite fauna.

            Termite control on the African continent is varied.  Some practices markedly differ from those in the Americas and Europe.  In northern Africa, measures range from commercial services to physical removal of queens and nests by hand.  Yet some control procedures are similar to those reported for the Americas and Europe, including soil applications (topical and injection) with the usual range of termiticides, as well as baiting.  For drywood termites, fumigation with methyl bromide1 and topical and subsurface chemical injections are the standard practice.  Future prospects for control include improved building practices, physical barriers, and use of baits and safer chemicals.  Termiticides, including organochlorines, are infrequently used due to lack of availability.  In western Africa, newer termiticides are not yet available.  Alternative methods for control include flooding termite nests with water.

Americas

The diversity of termites in North America is low compared to other regions of the world.  Less than 50 species are recognized; mostly subterranean and drywood nesters (see Basic Biology section).  Subterranean termites (important genera Reticulitermes, Coptotermes, Heterotermes, Family Rhinotermitidae) are the most diverse and widespread group of termites in North America.  There are > 24 species and they occur from below sea level to ~ 3,000 m.  Drywood termites (important genera Incisitermes, Marginitermes, Cryptotermes, Family Kalotermitidae) occupy a band approximately 35 degrees southward latitude across the continent.  In nature, they prefer hardwood scrub and forests at elevations < 1500 meters. In general, all termite species in North America prefer dead or decaying wood.

In the United States, > $ 1 billion (US) is spent annually for the management of termite problems in buildings and other structures.  Termite control in North America is highly regulated, both at the chemical manufacturer and service level.  Thousands of firms are licensed to practice termite control in North America.  Subterranean termites (Reticultermes, Coptotermes, and Heterotermes) are responsible for > 90% of the control and damage costs in the United States.  Drywood termites (Incisitermes and Cryptotermes) have lesser importance as structural pests.  Soil drenches with liquid termiticides dominate the control tactic for subterranean termites.  However, baiting has gained a large share of control market for subterranean termites.  Surveys of pest control firms reveal poor building practices are responsible for many of the subterranean termite problems.  Canada and Mexico also have commercial pest control firms and associations responsible for termite control in their respective countries.

Over 400 termite species are recognized in South America, with many more yet to be described.  Mound-building species and arboreal species are common in South America, in addition to subterranean and drywood termites.  Important termite genera include Nasutitermes (Family Termitidae), Cryptotermes, Neotermes (Family Kalotermitidae), Coptotermes, and Heterotermes (Family Rhinotermitidae).  In part because of the tremendous diversity and lack of experts, taxonomy remains a critical impediment to understanding termite biology and ecology in South America.  A species of the subterranean Reticulitermes, possibly santonensis, has become an introduced pest in Chile.  It now infests entire neighborhoods.  The current control method involves the use of a commercially available organophosphate termiticides applied to the soil.  However, a commercial bait system is now being evaluated and used in selected neighborhoods. The drywood termite Cryptotermes brevis is spreading and causing damage in the northern regions of Chile.  However, Neotermes chilensis (Family Kalotermitidae) is more widespread.  Its damage progresses slowly and control is rarely undertaken.

Asia

Most ecological groups, subterranean, drywood, harvester termites, and mound builders are found in China.  Common and important pest genera include Coptotermes and Reticulitermes (Family Rhinotermitidae), and Cryptotermes (Family Kalotermitidae).  Termites occur in many environments, be they natural or influenced by man.

For China, economic losses from termites exceed > $ 1 billion (US) each year.  Tens of thousands of tons of pesticides have been applied in the 13 provinces of southern China.  Infestation rates of buildings in Guangdong and Hainan provinces may be as high as 80%.  Pest control in China is state controlled and operated.  Termites also damage utility poles and the earthen walls of dams.  Many different chemicals are used in China for termite control.  They include fumigants (methyl bromide1 and phosphine), organophosphates, inorganic dusts, pyrethroids, wood preservatives (copper-arsenic) and a number of organochlorines.  Future prospects for control include using baits, physical barriers, monitoring, improved building practices and less dependence on the use of organochlorines. 

It appears Japan may be the third largest user of pesticides for structural pest control in the world.  Termites can be found everywhere in Japan except for the northern half of Hokkaido Island.  It is estimated that the cost of preventing and controlling termite infestations amounts to at least 800 million (US$) a year.

Australia

            More than 360 species of termites are described from Australia.  All termite ecological groups (subterranean, arboreal and mound builders, drywood, dampwood and harvester termites) occur in Australia.  The Australian termite fauna is also well known for its relict primitive genera Mastotermes, Porotemes, and Stolotemes (see Basic Biology section).   In-depth understanding of the biology and ecology of termites is restricted to 5 to 15% of the described species.  There are 16 key pest species of subterranean termites in Australia.  The cost for management and damage repairs for termites is estimated at > 100 million (Australian $) each year.  The 1995 ban on cyclodiene use triggered development of a diverse array of remedial and preventive termite management methods.  Termite management systems available include soil drenches; physical barriers, including properly constructed concrete slabs; baits; resistant materials; and biological control.  Australia is unique in the world in having developed national standards on termite management for whole-of-house protection.  Regulators and the pest control industry are close to implementing a national training and licensing system for pest control operators.

Europe

Europe has the smallest number of termite species in comparison with the other populated continents.  Fewer than 10 species have been identified in natural habitats.  Reticulitermes is the most common genus encountered.  It is widespread around the Mediterranean (Spain, France, Italy, Balkans, and Greece) and Black Sea (Turkey, Rumania, and Ukraine).  Five species have been described so far and a sixth is being studied.  Several unanswered questions remain about the origin of these termites.  While some Reticulitermes are native to Europe, others may be related to species from eastern North America and the Middle East (Israel, Asian Turkey, etc.).  In some parts of Europe, Reticulitermes kill living trees in urban areas.  This aggressive behavior is unusual for the genus.

Termite problems in Europe are increasing.  Introductions well outside the natural range have been reported from Germany and England.  The pest control industry in Europe, relevant to termite management, is small (< 200 firms). 

Costs for treatment and damage repairs will exceed 1 billion (Euro) within 5 years.  Termiticide applications are particularly challenging in Europe due to high density of buildings, type of construction, and historic age of many buildings.  Termiticides used today are primarily organophosphates and pyrethroids.  Newer chemicals (e.g., compounds that affect GABA receptors, such as imidacloprid and fipronil) and baits are gaining acceptance.  There are considerable differences between termite species in behavior and susceptibility to chemical barrier treatments.  The challenges pest control operators face will be in identifying which species are causing the problem and selecting safer and more environmentally friendly management methods.

 

III.7   Alternatives to POPs for management of Termite as Structural Pests

There are a number of disclaimers to be remembered before reading the following sections.  First, the following tables and suggestions for alternatives to POPs are not exhaustive.  Less than 20 experts, mostly researchers and one regulator created the following tables and suggestions.  Realistically, many countries have regulatory mechanisms and local expertise pertaining to termites and their management.  Local expertise within your country is very important and should be sought out when planning for alternatives to POPs.  Second, there are many alternatives to POPs.  However, they all are not equally effective and applicable to situations involving termites and structures.  Availability of products differs greatly between countries.  Remember that the perception of termites as pests is very important in deciding on management measures.  Changing from one chemical to another is not a long-term solution.  However, paying close attention to building design, site preparation, construction and regular building maintenance and inspections lead to long-term solutions.  Terms like prevention and elimination should be used with extreme caution when referring to termites.  The more appropriate and realistic terms used should be termite management systems that include regular building maintenance and inspections for signs of termites and breaches in barriers (chemical or physical).   Successful termite management is a process that includes the talents of construction, pest management, and building management professionals.  Lastly, termite management systems are most successful and least expensive pre-construction.  Conversely, they often are less successful and more expensive post-construction.  The following products and services mentioned do not represent an endorsement by UNEP or FAO.

As per treaty negotiations, use of all POPs for termite control is to be phased-out.  Initially, chlordane, heptachlor and mirex can still be used as termiticides in countries that are Parties to the Convention if they register for a relevant specific exemption that is included in Annex A of the Convention.  However, unless extensions are requested and approved by the Conference of the Parties, these exemptions will expire 5 years after the date of entry into force of the Convention2.  There are many alternatives to POPs for termite management/control (Table 1). Many of the management methods mentioned may not be commercially available for your country/locality and effectiveness and safety information also may not be available (See Process for Selecting/Testing Strategies section for information on evaluating effectiveness and determining appropriate alternative management methods.).  For all termite management systems, it is critical that label instructions and other specifications are followed.

 

III.8   Termite Management Systems in buildings and structures

Design of a Building

There are many steps that can be taken to prevent termite damage/infestations, Table 2 .  Design the building with termite management in mind. Determine the type of management system to be used first (for example specific physical or chemical barrier or combinations thereof, use of resistant materials for all structural elements) and select the appropriate building materials and practices.  In the design, allow for ease of inspection of the structural elements (for example removable skirting boards, slab-edge exposure, adequate crawl space).

Building design and construction techniques may contribute to termite invasion.  Construction techniques should avoid the use of wooden or other cellulose forms, spacers, and fill materials, unless these can be removed before construction is completed.  All wood (substructure, siding, doorframe, etc.) should be at least 30 cm above the soil.  Other structural deficiencies that attract or promote termite infestations should be identified and corrected.  Materials used for siding or cladding of buildings  (such as cement, stucco, stone fascia, wood fascia, etc.) must be kept from contact with soil at the foundation to prevent termites from entering the structure undetected behind these materials.  Attic and foundation areas should be kept well ventilated and dry.  Use screening over attic vents and seal other openings, such as knotholes and cracks, to discourage the entry of winged drywood termites.  Although screening of foundation vents or sealing other openings into the substructure helps block the entry of termites; these procedures may interfere with adequate ventilation and increase moisture problems, especially if a very fine mesh is used in the screening.  Ensure that attachments to buildings do not provide shelter or a hidden point of entry for termites.  Utility and service boxes may have to be sealed, downpipes and service pipes, steps, porches, ramps, trellises, air-conditions, etc., are to be separated from the building so that full inspection is possible. 

Reduce chances of infestation by removing or protecting any wood in contact with the soil.  Replacement of damaged wood is another remedial treatment option, Table 3. However, the effectiveness of wood replacement is highly dependent on detection accuracy and extent and location of the infestation, and it may be expensive to accomplish. Structural lumber in buildings varies around the world.  Some timber species are to a varying extent resistant to termites.  Usually trees and termites in a given area have co-evolved.  While a given species of tree may be resistant to the local termite fauna, termites from other parts of the world may be able to attack this species of tree. Hence, experiences with termite resistance of certain timber species are not necessarily transferable from one region to another.

Preservative-treated Timber Products

There is a wide range of panel products and structural lumber with several insecticides added that are available as a management option (Tables 1 & 3).  Termite susceptible wood can be turned into a termite resistant material by treating it with chemical toxicants (wood preservatives) that inhibit feeding by termites, and often growth of wood-degrading microorganisms.  Use of such timber can be effective and economical for some situations.  A list of commercially available active ingredients is provided in Table 3.  Wood that has been chemically treated will be protected from damage; however some minor termite feeding might still occur.  Termites, especially subterranean termites, might also build foraging tubes over or around and along cracks within the chemically treated wood to areas not so treated.  For these reasons, wood treatment is most successful in preventing termite infestations when used in conjunction with other termite management strategies, especially proper site preparation (removing cellulose debris and earth-to-wood contacts) and termite-resistant-building design.  Drawbacks for wood treatment include harmful effects to applicators and the environment, depending on the active ingredients and solvents used, type of application equipment and training given to applicators.  Some wood treatments require the use of pressurized chambers.  Disposal of treated wood during construction renovations and possible harmful effects to the public and environment are additional issues to consider when using this termite management strategy.

Historically, active ingredients for wood preservatives included creosote and pentachlorophenol.  However, because of environmental persistency and toxicity, most of the uses of these chemicals have been restricted or banned in many parts of the world.  Other active ingredients include chromated copper arsenate (CCA), ammoniacal copper quat compound (ACQ), and disodium octoborate tetrahydrate (DOT).  Wood containing CCA is tinted green, and ACQ is brownish. The surface of wood treated with DOT or borates are clear in appearance when used in accordance with label specifications.  Borates are gaining in popularity because of their low mammalian toxicity, water solubility, and ease of application.  There are many variables to consider when choosing wood preservatives, most important is whether they use is interior, exterior, and in ground contact.  The label on the wood preservative should be read carefully to insure proper usage.

Wood preservatives are most toxic to termites when ingested.  In the case of drywood termites, treated timber may also discourage new kings and queens (alates) from establishing colonies.  Pressure treatment is always favored over topical applications when using any wood preservative.  Care should be taken when using wood preservatives to ensure that all exposed wood is treated.  This includes spot applications at construction sites where lumber is cut and drilled for fasteners.

Physical Barriers

Physical barriers are made from a variety of inert materials, Table 4.  They may also contain other components, such as sealant and “glues” to join sheet material or woven mesh to bricks and concrete to provide a strong and durable bond.

Physical barriers fall broadly into two types: graded particles and sheet materials.  Particle barriers can be produced from sand, crushed rocks such as granite and basalt or crushed glass and consist of specific particle sizes that prevent termite tunneling when installed under or around foundation elements or penetrating conduits and pipes.  Barriers from sheet materials can be in the form of corrosion resistant sheets of solid metals or woven stainless steel mesh.  These types of barriers can also be installed under and around foundation elements or penetrating conduits and pipes to prevent termite invasions.  Concrete slabs produced to certain specifications (“engineered slabs”) that minimize shrinkage cracks, can also form a physical barrier. However, at joints and service pipe penetrations through the concrete slab, physical barriers must also be installed to prevent termite passage into the superstructure.

These physical barriers are designed to force activity of subterranean termites out into the open, where it can be detected during routine inspections of buildings and appropriate action taken.  In this context, it is important to note that physical (and chemical) barriers cannot entirely exclude the possibility of termite attack as barriers may be bridged or breached. Termite activity can be detected during regular inspections and appropriate steps for managing the problem can be taken.   Some of these measures can also be effective in managing problems with arboreal nesting species.  These recently developed physical barriers, such as stainless steel mesh and use of particle size barriers, are gaining popularity in their use for some countries.  These barriers are not appropriate for the protection from drywood termite infestations in structures.

Termiticide Applications to Soil and Non-soil Substrates

Termiticides applied to soil and/or wood have long been the traditional management strategy applied to subterranean, arboreal, and drywood termites for many regions of the world.  Typically these treatments consist of liquid, dust, or foam formulations applied to soil, wood, or aerial and arboreal nests (Table 5).  Treatment is aimed at creating a zone of treated soil between the wood in a structure and the termites.  Rodding and reticulation systems are sometimes used (closed, perforated tubing laid underground to distribute the chemical).  For drywood termites and arboreal nesters, the termiticide may be topically applied or injected via drill holes to inhabited wood or the nest

Newer application techniques include the incorporation of insecticides into fibrous matting or plastic laminates, thus avoiding direct treatment and contamination of soil with the chemicals.

Active ingredients in available termiticides can be broadly classified as repellent or nonrepellent.  Pyrethroids and synthetic pyrethroids (several brands are marketed) are considered repellent.  This means termites can detect the barrier before a toxic dosage is encountered.  Care in application is needed to minimize breaches in the barrier.  Termites that detect these materials may forage until they find a break in the barrier and "tunnel" into a structure through this break.  Examples of "nonrepellant" chemicals include organophosphates, imidacloprid, fipronil, chlorphenapyr (see Table 5 for more listings).

Active ingredients of toxic dusts that do not act as barriers  include arsenic trioxide, boron and many more (see Tables 3 & 6 for more examples).

Baiting Systems

Baits for subterranean termites are commercially available in a number of countries (Table 6).  This method of controlling termites is very appealing because it does not require extensive site preparation and uses significantly lower amounts of toxicant than soil treatment.  For example, baiting systems may use 1,000-fold less pesticide than a typical soil treatment for a similarly sized structure.  Key features of this treatment strategy involve the use of systems (bait stations) to aggregate termites to a few points close to the outside or inside of the structure and application of toxicants either to the food matrix in the stations or directly to the termites (dusts).  Termites carry the active back to the nest where it is passed along to nestmates via mutual food exchange or grooming.  Thus, bait technology targets the termite colony, although depending on circumstances, only reduction of the population may be achieved.  Active ingredients have to be slow-acting, nonrepellent chemicals to allow for uptake of significant amounts of the toxicant and transfer to nestmates. 

Bait systems are chiefly applied to active infestations of subterranean termites (effects for aerial and arboreal nesters are still unclear as at this time).   Dusts and biological control agents (Tables 6 and 9) can also be used in bait systems.  Research is currently focused on the use against different pest species, mixed species infestations, and varying environments.

 Space Fumigation

Space fumigation (Table 7) involves the introduction of a toxic gas inside a structure sealed inside a tarpaulin, or into or around an isolated area or object infested with subterranean termite aerial nesters, arboreal nests, and drywood termites. These gases must be used with extreme care, because they are extremely toxic to humans, as well as other animals, and plants.  Improper or careless use can result in death or injury.  Fumigants treat all termite infestations or colonies simultaneously, and have high levels of efficacy, if correctly applied.  Major issues to consider with the use of fumigants include the difficulty of installing tarpaulins to contain the gas within the structure, determining the proper dosage, the need to protect food items and certain furnishings in the structure, and the lack of residual control. Additional considerations with fumigant use are the need to vacate structures for 2 to 3 days for treatment and ventilation, and the possible damage to roofs caused by dragging tarpaulins or the activity of workmen.  Methyl bromide1 is a commonly used fumigant.  However, issues involving the atmospheric ozone layer, odor in some household materials after treatment, and long aeration times for fumigated structures have limited the use of this fumigant.  Methyl bromide1 is scheduled for phase out for international use in several years.

Thermal Control

There are four thermal options available for termite management, although mostly for drywood termites (Table 8).  They include electricity, heat from propane heaters, excessive cold from liquid nitrogen, and excessive heat from microwaves.  Many questions remain on their effectiveness and safety to humans and building materials.  Additional research will be needed before these methods are used on a larger international scale.  All of these thermal techniques have limited availability.

Biological Control

Experimental efforts have been made to control termites (mostly subterranean and arboreal nesters) using biological control agents, including fungi, nematodes, and argentine ants (Table 9).  Biological control is the use of other life forms (e.g., insects, nematodes, fungi, or microbes) to control pest insects.  Although predators, parasites, and pathogens have been shown to control other insect pests, their efficacy for termites is only just beginning to be explored.

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1 an ozone depleting substance

2 The Convention enters into force on the ninetieth day after the date of deposit of the fiftieth instrument of ratification