Termite Identification


.

Contents

Introduction

Social Structure
Life Cycle

Protecting Buildings against Termites

Making Buildings Unattractive to Termites

Site Preparation
Timber Alternatives
Resistant Timber
Timber Preservatives
Preventing Dampness

Making Termite Access Difficult

Concrete Slabs
Suspended Floors
Additions and Renovations
Attachments to houses
Physical Barriers
Chemical Barriers for New Buildings
Chemical Barriers for Existing Buildings

Inspecting for Termite Activity

Treating Active Infestations

Protecting Trees from Termite Attack

Further Readings
.

Introduction

Termites are small, soft-bodied, social insects that feed on wood, grass, dead leaves, bark, humus, fungi or the dung of herbivores. They are commonly known as white ants, but are not related to true ants.

There are over 2300 species of termites of which about 350 occur in Australia, and of these about 12 damage sound timber.

Termites also recycle organic materials and aerate the soil. They are an important part in the diet of other animals and their activities provide hollow logs, which are used by birds and mammals. Economically, the important termites are the subterranean species that usually nest under, or in contact with, the ground.

The following species do the most economic damage: Coptotermes acinaciformis, Coptotermes acinaciformis raffrayi, Coptotermes michaelseni, Mastotermes darwiniensis, Nasutitermes exitiosus and Schedorhinotermes reticulatus.

Note that the suspected occurrence of drywood termites, or other unusual damage to timber, should be reported to Agriculture Western Australia. Drywood termites nest in wood above the ground and do not require contact with the ground.

Social structure

Each termite colony may comprise more than a million insects divided into specialised groups called castes. Each caste is physically different and performs a particular function.

Primary reproductives (Life Cycle) are the king and queen that established the nest after leaving existing colonies. In an established nest the queen may be enlarged and practically immobile. In some species, the queen can lay 2000 to 3000 eggs per day. The king and queen may live for 15 years and are replaced when too old to meet the needs of the colony. The king periodically fertilises the queen, unlike bees, wasps and ants where the queen usually mates only at the beginning of her reproductive life.

Winged reproductives or alates are the future kings and queens of new nests. They have a well developed cuticle, compound eyes, and two pairs of usually dark brown elongated membranous wings of equal length. Alates disperse in large numbers from mature colonies, usually in warm humid weather. They are weak fliers and quickly land and drop their wings. The females release a scent (pheromone) to attract a male with which to establish a nest. Only a small percentage are successful in establishing new colonies. It takes several years of development before a nest can do significant damage. Alates are only produced in well-established, mature nests. During their dispersal flight, alates commonly land on the roofs of buildings and move inside. This is not a matter for concern since they must first establish a nest in the ground. However, alates seen emanating very close to the house suggest a nest is nearby and a pest control operator should be contacted.

Soldiers are sterile males and females. Their main function is to protect the colony. They also scout and locate new sources of food. Soldiers have a thin, white or light brown cuticle over most of the body and a thicker, dark brown cuticle covering the head. Soldiers are physically distinctive and are the primary group used for species identification. Soldiers cannot feed themselves and are dependent on the workers for their nutrition. Some soldiers exude an acid fluid as a means of defence. This fluid can corrode metal and will penetrate mortar and low grade concrete.

Workers are the sterile males and females that feed the colony, rear young and repair and enlarge the nest. They are the only caste that can chew and digest the cellulose in wood. Workers have thin cuticles and are the most numerous caste of the colony.

Workers, soldiers and the enlarged queen are very susceptible to desiccation owing to their thin cuticles. Thus the humidity of the nest is kept at 90 to 95 percent. When termites are forced to cross a structure that they cannot eat, they construct mud-like shelter tubes (or galleries) which protect them against light, desiccation and predators.

Life cycle

The life cycle of termites is described as "incomplete metamorphosis" with egg, nymph and adult stages. In the nymph stage termites grow through a series of moults. The life cycle of true ants is known as "complete metamorphosis"; with egg, larvae, pupa and adult stages.


Figure 1


.

Protecting buildings against termites

Termites are active in nearly every residential block, although not all damage timber.

Isolating the superstructure of the house (containing the edible components) from the ground is the most important part of protecting it from termite attack. This can be done in three ways:

  • Make the building unattractive to termites;
  • Use barriers and design features to prevent termites invading the building;
  • Ensure the building is easily accessible for termite inspection.

Making buildings unattractive to termites

Termites are especially attracted to timber that is damp and infested with wood-decaying fungi. Proper site preparation, the use of timber alternatives, termite resistant wood and timber preservatives, and prevention of dampness will deter termites.

Site preparation
All tree stumps, roots, other wood and timber products (for example, cardboard and paper) should be removed from the new house site or burnt before construction. Avoid the use of wood in direct contact with the ground. Attach wooden posts to steel fittings concreted into the ground with 50 to 100 mm between the wood and the ground. Seal the top of steel fittings fabricated from hollow tubing with welded plate to prevent concealed termite penetration.

Keep stacks of timber or firewood well clear of existing buildings. However, termites on firewood brought inside are unlikely to cause an infestation as the queen will not be located in surface timber and workers isolated from their nest will die. Avoid using timber in garden landscaping and retaining walls. Even naturally resistant timber, such as jarrah, could become subject to attack under damp conditions. Timber in gardens may encourage termite activity and increase the likelihood of the establishment of new termite nests.

Timber alternatives
Steel trusses in roofs and steel door frames are practical alternatives to timber.

Resistant timber
Use resistant timber where possible, especially in exposed positions or in contact with the ground.

Resistant timbers are wandoo, blackbutt, jam, jarrah, western red cedar and kapur. Also resistant are the Australian native cypress pines and Australian cedar.

Susceptible timbers include pine, karri, marri, mountain ash, meranti and particle board. All sapwood, even of resistant species, is susceptible.

No timber is totally resistant to attack.

Timber preservatives
Creosote can be an effective timber preservative, preventing termite attack and wood rot. Protection depends upon the depth of penetration. Simply brushing creosote on wood surfaces gives little protection. Multiple applications by brush are better, but preferably soak the timber in creosote for at least 48 hours. All cutting and hole boring should be completed before soaking. Round fence posts of seasoned softwood timber, with sapwood present and the bark removed, can be successfully treated in a similar manner.

Stand posts 'top down' for at least one hour in 1 to 1.5 m depth of creosote in a 200 L drum. Then, invert the posts and soak the butts (timber in contact with the ground) for several days. The preservative readily enters sapwood. For butts, the rate of absorption should be 160 g/L of sapwood. Tops require about one-third this rate.

Softwoods, such as pine, can be effectively treated with salts of copper-chrome-arsenic (CCA). This gives the timber a greenish appearance and can protect against fungi and termites for more than 20 years.

The heartwood of Australian hardwoods cannot be effectively treated because it is dense and resists penetration by the preservative.

Preventing dampness
Ensure that storm water is shed away from buildings using paving sloped at an adequate angle away from the foundations. Direct gutter outflow to storm water drains or soak wells situated well away from the foundations. Avoid placing garden beds and associated reticulation adjacent to the house foundations. Never construct raised garden beds abutting the outside wall of the house. Internal gardens or conservatories can create special problems and owners should consult the architect or builder about protecting these from termites.

Dampness around bathrooms and laundries in houses with suspended floors causes special concern, since tile grout allows moisture to seep through. Pre-formed fibreglass shower floors, which don't allow water seepage, can be used in some circumstances. Water and sewerage pipes under buildings should be free of leaks.

Correctly fitted air vents provide adequate ventilation of sub-floor spaces and keep timber dry. They also provide light, which termites find repellent.

Making termite access difficult

Building design and physical and chemical barriers are effective ways of preventing termite attack.

Concrete slab-on-ground construction
Concrete slab-on-ground construction is the most common type of construction, but is susceptible to termite entry. Concrete slabs, which retain moisture under them, attract termites.

Standard building practices involve pouring the concrete in two stages. The foundations are laid first and then the concrete slab is poured to overlap the foundation. The joints between the foundations and slab can crack giving termites access to the cavity walls (see Figure 2), roof and other timbers.

Covering the bottom one or two courses of the outer leaf brick wall with soil is the most serious design flaw in standard constructions. This provides termites direct concealed access to the cavity walls and from there to most structural and cupboard timber in the house (see Figure 2).


Figure 2

The common practice of using thinner concrete, or no concrete at all, under the bath markedly increases the risk of termite attack in the bathroom area.

The concrete slab can act as a physical barrier (see AS 3660.1-1995) itself, if it is constructed correctly to a minimum specification which satisfies AS 2870.1. The use of vibrators for compaction is strongly recommended.

Pouring the foundations and slab in one operation (monolithic slab) and bonding the two with steel reinforcements significantly protects the cavity walls and is recommended (see Figure 3).

Make the outer edge of the concrete foundations clearly visible. Ideally 75 mm of concrete should be clearly visible above the final finish level of the soil (see Figure 3). This markedly increases the building's resistance to termites. Exterior formwork is required to produce a 'finished' edge to the concrete which can then be painted to make it less obvious.


Figure 3

Termites can enter a building through the cracks and along air pockets formed around plumbing and electrical service pipes installed in the concrete. Using a mechanical vibrator on the concrete in these areas can improve the resistance of the structure. Penetrations through the slab (plumbing, electrical and other service pipes) and any joints in the slab need to be protected by a suitable chemical or physical barrier. Chemical barriers are required to be continuous under the entire sub-floor area.

Using adequate steel reinforcing and 'haunched' footings under internal, load bearing walls can help stop the slab cracking. Allow at least seven days curing time before heavy loads (for example, vehicles, brick stacks) are allowed onto the surface and before construction starts.

Suspended floor construction
Houses with suspended floors on steel or brick and concrete piers fitted with termite caps or shields, with adequate clearance (400 mm minimum), ventilation and light are the most termite resistant. Possible access points are steps, service pipes or the concrete slab-on-fill construction, often used under wet areas such as laundries and bathrooms. Steps should be separated from the house by at least 50 mm.

Additions and renovations
Design additions and renovations so that the superstructure of the building remains isolated from termites. Modifications can significantly increase the vulnerability of the building to termites.

Attachments to houses
Patios, pergolas, gate posts and steps can make a building more vulnerable to termites. Free standing patios and pergolas should be separated from the house by 50 to 100 mm. If they are attached to the house, pay attention to where they contact the ground. Avoid using wooden posts in direct contact with the ground. Attach wooden posts to steel fittings concreted into the ground with 50 to 100 mm between the wood and the ground. Seal the ends of hollow steel fittings in all constructions with welded plate to prevent termites entering the wood through the tubing. Ensure a 50 to 100 mm clearance between gate posts fixed in the ground and the building. Alternatively, gate posts fixed to the building should clear the ground by 50 to 100 mm.

Sheds
Similar principles apply to the construction of sheds. Avoid embedding timber posts directly into the ground. All timber should be clear of the ground by at least 50 mm.

Physical barriers
Place termite caps or termite strip shielding between the building superstructure and its foundations in constructions with suspended floors. Physical barriers are constructed from metal with the edge angled downwards at 45 degrees. Correctly constructed strip shielding can act both as a damp course and termite barrier.

Effective physical barriers need adequate site preparation. Remove all timber and builder's rubble from the site. Construction of these barriers is covered by Australian Standard 3660.1-1995.

Termite caps and strips do not provide complete protection against termite attack. However, where an attack occurs, they force termites to build their shelter tubes where they can be detected easily and treated. Thus, where physical barriers are used, provide adequate access for regular inspections.

Stainless steel mesh (TermiMesh®) is approved for use as a termite barrier. A layer of steel mesh, with holes too small for termites to penetrate, provides a barrier against attack. Stainless steel mesh barriers are best installed during the construction of the building, since fitting the mesh after construction is difficult and not as effective.


Figure 4

There are two basic options for installing stainless steel mesh to concrete raft constructions. The first involves a complete cover (see Figure 4) under the entire floor with clamp fittings around any pipes that penetrate the slab. This is the most expensive option ($4000 to $5000 per building) but provides the most complete protection. Partial installation (see Figure 5), across cavity walls and around the pipe penetrations only, reduces the cost substantially (about $1000, which is comparable in cost to a complete chemical treatment) and gives protection against most instances of termite penetration.


Figure 5

Installation of stainless steel mesh involves only an initial cost, but competent annual inspections are required. Partial installation requires an upgraded slab which conforms to Australian Standard 2870.1-1988: Residential slabs and footings. Part 1: Construction.

Graded stone has been accredited as a physical barrier. A base of compacted gravel of a specific size range is laid under the normal concrete pad. The method works on the principle that the individual granite particles are too heavy for individual termites to move and are too small to provide gaps large enough for the termites to penetrate.

Graded stone can be installed as a complete barrier under the concrete slab or as a partial barrier where it must be restrained so as to remain in contact with the other surfaces which comprise the barrier. Refer to AS 3660.1-1995 for installation requirements. When used as a partial installation, the concrete slab must conform to specifications set out in AS 2870.1.

Chemical barriers for new buildings
Chemical barriers must be continuous under the whole of the structure to be effective. Partial installation of chemical barriers is not sanctioned by AS 3660.1. All foundations should be surrounded by, and be in contact with, an insecticide-treated layer of soil.

Form chemical barriers after completing all site works ­ levelling, excavation, filling and compaction; and after the installation of ground-located electrical conduits and plumbing pipes. This is immediately before laying the floors of buildings with suspended floors or immediately before placement of waterproofing membranes for buildings with concrete floors. Table 1 shows the chemicals registered for use as termite barriers and their application concentrations.

Table 1: Insecticides for soil treatment of buildings under construction to protect against subterranean termites.

Insecticide (*)

Concentration to use
(**)

Trade Name

Bifenthrin

1 g/L south of the Tropic of Capricorn; 1.5 g/L north of the Tropic of Capricorn.

Biflex® Preconstruction Termiticide

Chlorpyrifos

10 g/L south of the Tropic of Capricorn; 20 g/L north of the Tropic of Capricorn.

Dursban® Preconstruction Termiticide

(*) Registered in Australia; Check regulations in your country first
(**) Grams of insecticide (active ingredient) per litre of solution.

Apply the emulsions of the insecticides listed in the table uniformly, at not less than 5 L/m2 for horizontal barriers. Vertical barriers in contact with foundations require 100L/m3 of soil and should be 150 mm wide against the wall to be protected.

Requirements for installing soil insecticide barriers against subterranean termites, for buildings under construction, are given in AS 3660.1-1995.

Prospective home builders should be aware that chemical barriers will not last the life of the building. Re-treatment intervals of six to 10 years are stated on the respective chemical labels. Re-treatments may not be required after this period but annual inspections by a licensed pest control operator are recommended. Re-installation of a chemical barrier underneath a concrete slab may require floor coverings to be removed, holes drilled through the floor and chemical injected unless an approved reticulation system was installed at the time of construction.

Site preparation can maximise the effectiveness of insecticide barriers. Remove all stumps, tree roots, timber and other debris before treatment.

For slab-on-ground constructions, chemical barriers can be installed only at the time of construction (except where under-slab reticulation systems are used - see below).

Below-standard termiticide applications involving understrength termiticide concentrations and reduced volumes of termiticide per unit area have been reported. As a guide, in October 1995, the cost of a termiticide barrier underneath a concrete slab (pre-construction) was about $5.25/m2, including the perimeter. Consumers should be wary of quotes which differ much from this figure.

Similarly, to apply 5 L/m2 of termiticide via low pressure spray is time consuming and could take more than one hour per building site.

These costs can be substantially greater above the Tropic of Capricorn where higher chemical rates are required.

Correct installation of a chemical termite barrier involves at least two separate treatments. The major barrier is under the concrete slab as described above. The final treatment is to the outer perimeter of the foundations after all service connections have been completed and all backfill is in place. An initial treatment to the foundations is also required where these are poured separate to the concrete slab.

All these treatments are part of the complete termite barrier as described in AS 3660.1-1995 and should be included in the building contract.

Concrete garage floors are usually poured separately and late into the construction of a house. Hence, they are often untreated and can weaken a building's termite protection. Chemical barriers are required to be continuous under concrete floors, including garages and carports.

If the garage is part of the house and is under the main roof, this treatment is the responsibility of the builder and should be included in the building contract.

ALTIS® and Termguard® are under-slab reticulation systems currently approved for use. They are installed pre-construction, underneath the slab and waterproof membrane. A chemical barrier is installed by injecting the insecticide under the slab at any convenient time between pouring the slab and completion of the house.

If a reticulation system is installed, it must be charged with chemical soon after the house is completed to satisfy building requirements.

The exposure of children to the termiticide barrier applied around the outer perimeter of a building is not considered a significant health risk. This is partly owing to the binding of the chemical to the soil and the evaporation of the solvents and emulsifiers soon after application.

It is possible to dispense with this treatment if the outer edge of the concrete slab is exposed 75 mm above the final finish level of the soil (see Figure 3).

Chemical barriers for existing buildings
Treat existing buildings with bifenthrin (Biflex®) or chlorpyrifos (Chlorpyrifos PCO®, Deter® or Dursban®). Higher rates (refer to the pesticide label) are required north of the Tropic of Capricorn to control the giant termite, Mastotermes darwiniensis.

Where the sub-floor area cannot be reached, a trench extending down to the top of the foundation and 150 mm wide around the outside of the building is an option. Dig the trench in contact with the foundations and then backfill it with treated soil using 100 L/m3 of insecticide emulsion.

Another application method for external barriers is to pump insecticide emulsion through a specially designed perforated pipe. The pipe is driven into the ground around the perimeter of the building, close to the foundations, to a depth of 300 mm at frequent intervals so that insecticide from adjacent injections meet.

Do not plant large trees close to buildings, since tree roots can broach insecticide barriers.

Inspecting for termite activity

All houses should be inspected annually. Licensed pest control operators are the best agents to carry out inspections. A thorough inspection could take two or more hours, depending on the construction of the house, and consumers should expect to be charged accordingly. An inspection should result in a signed, written report detailing the findings and indicating areas that could not be inspected adequately.

Australian Standard 3660­1993 and Verkerk (1990) give instructions for home owners inspecting their own homes.

Inspection for termites should be made simple. For slab-on-ground construction, the outer edge of the concrete slab should be easily accessible. Provide a minimum crawl space of 400 mm between the ground and the floor in suspended floor construction.

The perimeters of all buildings should be unimpeded by plants or similar. Allow 50 to 100 mm between steps, gate posts and other adjoining structures, and the building for easy inspection. Where extensions abut the house, ensure the join is unobstructed.

Note: It is in the interest of home buyers to arrange and pay for the inspection and Termite Free certificate when purchasing a house so they, and not the vendor, are the client of the pest control operator.

In this way the buyer can be sure of the standard of inspection and can exercise consumer rights without intervention from the vendor after the purchase, if problems arise later.
.

Treating active infestations

Termites are commonly found in gardens but their presence is not necessarily cause for concern. Building protection relies on effective barriers and not on the presence or absence of termites.

Disturb active termite infestations in a building as little as possible before treatment.

Identify the termite species before treatment, since this may have a bearing on the measures required. Termites are identified from the soldier caste. It is often possible to collect them, and minimise the disturbance of the colony, by inserting a smoker's pipe cleaner, blade of grass or similar into the galleries. The soldiers attach to it and can be kept in a collection bottle for identification.

Thoroughly inspect the building and surrounding area to locate all termite activity. The termite nest is usually below ground and may be up to 100 m away.

Forming a physical or chemical barrier between the termite nest and structure to be protected, or dusting the termite galleries with arsenious oxide, are options for treating an active infestation.

Leave treatment of active termites in an existing building to a trained Pest Control Operator. Arsenical dust can be dangerous to use and is not available to the public.

Australian Standard 3660-1993 covers the treatment of termites in buildings.

Arsenical dust treatment involves puffing finely powdered arsenious oxide into the termite galleries with as little disturbance as possible. The dust must be very finely ground (able to pass through a 75 µm test sieve) so that it does not block the galleries. It relies on the termites continuing to work as normal.

The dust adheres to worker termites and is spread through the colony by mutual grooming. As dead termites are cannibalised, the whole termite colony can be killed.

Locate and treat as many sites of the termite activity as possible, especially if they occur over a wide area.

Leave termite galleries undisturbed for two to four weeks and then arrange for re-treatment if necessary. Once termite activity has ceased, damaged timber can be replaced.

Once treatment is completed, any nests found should be excavated and sprayed with an appropriate insecticide.

While this treatment may kill the termite nest, it does not provide a barrier. The building remains susceptible to termite attack from other termite nests.

Alternatively, active termite infestation in an existing building may be treated with chemical or physical barriers (as above).

Care should be taken when treating buildings and yards in which animals used for human consumption are housed.

The chemical mirex is registered for use, in bait formulation, against the giant termite, M. darwiniensis, only. Licensed Pest Control Operators must be registered to use it. If mirex is used on trees producing products for human consumption, the trees must be removed and destroyed once treatment has been completed to prevent human exposure to mirex.
.

Protecting trees from termite attack

Clear the area of material that could attract termites before planting trees. Burn or completely remove tree stumps. In areas of high termite activity, the hole and soil may need treatment with bifenthrin (Biflex®) or chlorpyrifos (Chlorpyrifos PCO®, Deter® or Dursban®) during planting. Take precautions to prevent personal exposure to the insecticide during this operation.

Wooden stakes of susceptible timbers or sapwoods used for supporting plants can attract termites, as can mulches of woodchips, barkchips and nut shells.

Paradichloro-benzene (commonly available as toilet deodorant blocks) may be used where roots of young or small trees are attacked by termites. This chemical has a fumigant effect and, in flaked or crushed form, can be dug into the ground under the canopy about 15 to 25 cm from the base of the plant.

Alternatively, bifenthrin (Biflex®), chlorpyrifos (Chlorpyrifos PCO®, Deter® or Dursban®) or maldison (Maldison 500®) can be pressure injected around the base of the affected tree. This is only likely to be effective with small trees.

For large trees being attacked by termites, a termite nest may be located in the base. Using a long auger or spade bit, drill several holes (12 to 15 mm in diameter) around the circumference of the tree at a height of 500 mm above ground level and down at a shallow angle (see Figure 6). Live specimens or an obvious hollow inside the trunk filled with termite workings may indicate the presence of termites.


Figure 6

Treatment involves application of bifenthrin, chlorpyrifos or maldison via the holes to the nest. More than 5 to 10 L of diluted insecticide may be required.

This information is available in the form as Bulletin No. 4265 (Agdex 612), from Agriculture Western Australia.

Note: Mention of trade names does not imply endorsement or preference of any company's product by Agriculture Western Australia, and any omission of a registered trade name is unintentional.

The information provided here is according to Australian regulations. Before attempting to follow the information provided here, please check the regulations in your country.
.

Further Reading

Australian Standard 3660.1-1995. Protection of Buildings from Subterranean Termites. Part 1: New Buildings.

Australian Standard 3660-1993. Protection of Buildings Against Subterranean Termites. Prevention, Detection and Treatment of Infestation.

Australian Standard 2870.1-1988: Residential slabs and footings. Part 1: Construction.

Creffield, J.W. (1991). Wood Destroying Insects, CSIRO, Melbourne.

Harris, W.V. (1971). Termites - Their Recognition and Control, 2nd edition, Longman, London.

Shedley, P.N. and Challis, D.J. (1984). Mechanical Properties of Timbers Commonly Used in Western Australia, Forest Department of Western Australia Technical Paper No. 7.

Verkerk, R. (1990). Building Out Termites, Pluto Press (Aust. Ltd), Leichhart.

Watson, J.A.L. and Gay, F.J. (1991). Isoptera (termites). In: The Insects of Australia, 2nd edition, Melbourne University Press, Melbourne.

Links to other termite Internet sites in Australia:
Dr Don's Termite Page
Termite Control IPM from CSIRO

 

 

Author: Peter Davis