Subterranean Termites

Scientific Name: Coptotermes, Schedorhinotermes, Nasutitermes, Mastotermes, Heterotermes and Microcerotermes genera.

How to identify a subterranean termites

Members of the Coptotermes genus are easily distinguished from other termites when the soldier is poked or lightly squeezed, upon which a white milky liquid is secreted from a specially modified pore (fontanelle) in the front of the head as a defence mechanism.

Schedorhinotermes is easily identified from other termites in that the soldiers come in 2 sizes. The major soldier is approximately 6mm in length and has a bulbous shaped head whereas the minor soldier is only around 4mm long with a narrower head and more slender mandibles. Identification between species can be difficult however the geography of where they are found can be useful. The most common Schedorhinotermes species that pest managers may encounter can be found below:

Mastotermes is the most ancient living genus in the world and contains only one species: Mastotermes darwiniensis. The large size of the termites and associated galleries in damaged timbers plus where they are found makes identification easy.

Nasutitermes is the most evolutionarily advanced termite genus and can be easily identified by the pointed snout or nasus at the front of the soldier’s head. Identification between species can be difficult; however the geography of where they are found and the presence and type of mound can be useful. 

Heterotermes are generally considered less of a threat to timber in service than the afore mentioned genera, however in parts of northern Australia they have caused considerable damage to houses. This termite is often confused with Coptotermes as the soldiers look similar except that the head of the Heterotermes soldier is a more longer and rectangular, compared to the tear drop shape of the Coptotermes.

Microcerotermes The soldier has a rectangular head resembling Heterotermes except for the presence of fine serrations on the inner margin of the mandibles

Where are subterranean termites commonly found?

Subterranean termites are mostly ground-dwelling and require soil contact for a source of water (can survive in houses above ground if an internal source of moisture exists). Subterranean termites by far cause the most damage to timber in service in Australia. There are approximately 15-20 species of subterranean termites which commonly attack timber in service throughout Australia

Why are subterranean termites considered a pest?

Termites consume cellulose in one form or another and play a crucial role in nutrient cycling and helping create soil structure through the decomposition of wood and plant debris. They only become a “pest” when they attack timber in service or damage crops and other materials important to humans.

Termites are known to damage materials that have no nutritional value during their search for food. These include rubber, plastic, leather, mortar and some metals. A particularly annoying trait is the attack on underground power cables, with termites chewing through the outer rubber and plastic sheathing, thus exposing the conducting wires to moisture resulting in short circuits and ultimately power failure.

What is the biology and lifecycle of subterranean termites?

Termites metamorphose through egg to nymph to adult. By several moults, the young nymphs then differentiate into one of several castes. This may take several months, depending upon food availability, temperature, and the colony’s vigour. Within a termite colony there are several forms (castes); namely a queen, king, workers, soldiers, and periodically, reproductives. Each caste is structurally different with specific functions to perform for the colony’s survival and maintenance.

Chemicals Required to Control Subterranean Termites

Liquids – The traditional method dating back many decades whereby a chemical is incorporated into the soil surrounding and/or under a structure to prevent termite entry. These can be grouped into either repellent or non-repellent based on their effect on termite behaviour when they contact the treated soil. Repellent products repel foraging termites from a treated structure whereas non-repellent products are undetectable to termites and when they contact the treated soil, they are either killed quickly or pick up a sub-lethal dose(becoming intoxicated) which may allow transfer to other termites away from the treated area.

Dusting – Widely used by pest managers in Australia for many years. Started out with arsenical based dusts followed by more recent chemistry. They are basically a toxicant mixed with a carrier that is blown on to a population of termites. The termites then carry the dust on their bodies to other parts of the colony and transfer the toxicant to non-treated termites and hopefully resulting in colony collapse.

Foaming – A surfactant and termiticide are mixed and delivered directly into active termite infestations under air pressure via a foam generator or a ready to use pressurised “aerosol”. The foam rapidly expands and moves through the gallery system under pressure and can even move upwards to coat as many termites as possible. If using the right active ingredient, foaming can also be transferred away from the site of treatment to effect the population as a whole.

Baiting – Above ground baits containing a matrix of attractive cellulose based food plus a toxicant, are placed over the site of termite activity. If termites are enticed to begin feeding on the bait, the toxicant is introduced into the colony and spread to others. The toxicants of choice at the moment are insect growth regulators (functioning as a chitin synthesis inhibitor), which disrupts the moulting process, ultimately causing death during the process of shedding their exoskeleton.

Baiting Systems –  Plastic stations are placed either at regular intervals or in termite conducive areas and filled with an attractive cellulose bait eg: timber material. Once termites are attacking the bait, a matrix of cellulose powder and a toxicant is added to the station for the termites to continue feeding. If termites are enticed to begin feeding on the bait, the toxicant has now been introduced into the colony and spread to others. The toxicants of choice at the moment are insect growth regulators (functioning as a chitin synthesis inhibitor), which disrupts the moulting process, ultimately causing death during the process of shedding their exoskeleton.

Others – There have been a number of attempts to bring new technologies to the market that have either failed or are yet to take off eg: specific fungal strains, nematodes, gel and paste formulations, with more to come in the future.

Management Tips for Subterranean Termites

Pre-construction can be defined as the time period immediately before the actual structure of the house is constructed and is all about prevention.

Building site management – It is a requirement under Australian Standard 3660.1, that prior to any construction beginning, any nest or colony of economically important termites found within 50m of the building site are to be eliminated. Also that any stumps, logs, timber off cuts or any cellulose based waste materials on the footprint of the building be excavated and/or removed.

Physical barriers - The purpose of installing physical barriers is to deter concealed entry by termites into a building. They include sheet metal (traditional “ant caps” and woven stainless steel mesh), chemical barriers in a non-soil matrix (impregnated plastic sheeting, pellets and discs etc), graded particles (stone, glass etc) and the actual concrete slab itself (if poured to the relevant Australian Standard). It must be remembered that termites can easily build around such barriers but their workings are then in the open where they may be detected upon regular inspections and then treated with traditional chemical methods. Physical barriers are required to last the nominated life of the house.

Liquid treated zones – Have a similar purpose as physical barriers in that they deter concealed entry by termites into a building but have the extra advantage in that if installed correctly, can make it very difficult for termites to build around the treated zone. These are installed as either horizontal or vertical zones which involve incorporating the chemical into the soil via trenching, hand spraying and other various methods such as piped reticulation. Chemical treated zones are designed not to last the life of the house and must be replenished at intervals as stated on the product label.

Post-construction - refers to any time period after the completion of the house and treatment can consist of either curative, preventative or both management techniques.

Curative – Also referred to as a “Stage 1” treatment and is designed to rid the structure of active termites to limit the amount of damage and if possible, eliminate the colony from which the termites were originating from. Curative treatments are not meant to be stand alone treatments and should be followed up with a preventative treatment as soon as termite elimination has been confirmed in the structure.

Preventative – A “Stage 2” treatment to follow up from a successful curative (Stage 1) treatment or in a structure that did not have a live termite infestation.

Pest Managers should not solely focus on the structure for helping prevent termite attack. Every medium to large tree in the surrounding yard should be drilled and checked for termite nests. Any activity of economically important species should be treated with a dust, foam or liquid termiticide. Aggregation devices in conducive areas (gardens close to the structure, wet areas etc) around the structure are also helpful to get large numbers of termites to facilitate a dust or foam application. Other activities that pest managers can advise homeowners to undertake to help reduce the risk of termite ingress includes: fixing any water leaks in and around the home, remove any timber laying around, improve ventilation in sub-floor areas, make sure gardens etc are below the height of the dampcourse and of course, regular inspections by a licensed pest manager.