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How do chemical soil treatments protect buildings from termite attacks?

A chemical soil treatment involves the application of liquid termiticide to the soil around and under buildings, using high volumes of termiticide to saturate the soil. The timbers themselves or house internals are not treated.

The idea is to create a ‘treated zone’ that prevents termites travelling through the soil and up the footings to access the building.

The effectiveness of such a treatment is reliant on ensuring a complete and continuous treated zone that integrates with the structures of the building such as a concrete slab or concrete strip footings. When installed continuously in an unbroken barrier in contact with the building’s concrete footings, this is likely to prevent concealed termite entry to the building. Obviously, any gaps in the treatment or cracks in the building footings can allow termites to access to the structure- just like leaving a gate open in a fence around a paddock.

Chemical applications are not intended to kill termites or termite colony nests. They also won’t stop termites from turning up in nearby areas or landscaping that have not been treated. They are simply designed to prevent concealed termite ingress to a treated building. Termites can sometimes even ‘bridge’ over the top of a chemically treated zone to gain access to your home. The good news is that if they do this, their activity may be detected during the recommended regular termite inspections, and the problem dealt with before significant damage is done.

Call us on 1300 695 949 if you think you may have termites

Repellent chemicals

Conventional termiticides are repellent chemicals – the termites can detect their presence in the soil and avoid the treated area. These materials can provide a very robust barrier in the soil to termites. However, if there is a gap in the treated zone, the termites may detect that gap (that is not repellent) and exploit it to gain ingress into a building. A positive of these repellent chemicals is that they have a greater longevity then others products thus require less reapplication and are typically less expensive than their more modern non-repellent counterparts.

Non-repellent chemicals

The newer termiticides are ‘non-repellent’. Termites cannot detect their presence in the soil and will enter a treated zone and become contaminated instead of repelled. These termiticides are considered more ‘forgiving’, in that if there is a gap in the treatment (as is almost inevitable) ant termite trying to access the building is unable to detect the areas of untreated soil and purposely bypass it. The chances of the termites accidentally walking through an untreated area without also passing through a treated area are low. Not surprisingly, these modern termiticides are more expensive than the traditional repellent chemicals.

Termite barrier or treated zone?

Chemical soil treatments are often called termite “barriers”. Historically this came about since all chemicals were repellent to termites. Termites coming into contact with this treated soil around the home would be repelled by the chemical, preventing them from entering the home – an invisible, protective “barrier”.

When modern non-repellent termiticides are applied as protection around a building, a non-repellent ‘treated zone’ is created – not a ‘barrier’. Termites can penetrate through the treated area and even enter the building- for a while! Then they become sick and die- but not before they have spread their contamination around with their family members though their habit of ‘trophallaxis’. (passing food from one to another)

Termiticide treatments of both kinds are intended to prevent concealed access by termites, but cannot prevent the possibility ‘bridging’ around treated soil. Annual inspections after a termite treatment are recommended in order to locate and treat and such ‘bridge’ into the building.

Chemical soil treatment or termite monitoring system?

Chemical soil treatments can be very effective, but whether we recommend a chemical soil treatment as an option for your building will very much depend on the structure’s construction and environmental conditions around the property. Chemical treatments are simply not suitable for all construction types and situations. Any scenario that makes the application of a continuous treated zone impractical, makes the protection of buildings with chemicals less practical or more intrusive and damaging. For example, buildings with joins between concrete slab (for an extension) or buildings without safe sub-floor access cannot be properly protected. We will not recommend a chemical barrier for a building where restrictions mean that the barrier will not be reasonably complete. We do not like the idea of a 90% barrier because it gives a false sense of security to our clients, and possibly an unpleasant phone call after a year or two. In our experience, termites seem to be pretty good at finding the gaps! We will always evaluate the situation at your property and discuss the options available, the pros and cons, so you can make an informed choice for the best termite treatment for your property and your situation.

As a general rule, where on-going protection is required, but a ‘treated zone’ treatment can’t be applied as a continuous unbroken zone, then we are likely to recommend a termite monitoring system.


Chemical barrier treatments

Chemical barrier treatments are typically carried out on existing properties. It maybe applied to prevent a termite attack or as part of a treatment on a house that has suffered a termite attack, to prevent further attacks in the future. Our team will also tend to apply a termite chemical barrier after we’ve carried out colony location and destruction for an existing home or building, as well as possibly using dusting and baiting techniques to remove existing termites on your property.

Our termite chemical barrier treatment consists of a liquid termiticide that is applied to the ground using high volumes flooded into soil, which prevents termites travelling through the soil and into the footings of your building. We generally combine this method with assessing the physical barriers created by features of your building to create a single, effective barrier around your property.

Significant changes to liquid (soil applied) termiticides recently

We will not discuss those termiticides that are solvent based and smelly. We exclude these as unacceptable to us and to our clients. This leaves water based and odourless materials. These can be split between REPELLENT and NON -REPELLENT termiticides.
REPELLENTS – These are the traditional type, and include a large range of pyrethroids that are man made copies of the low toxicity “Pyrethrum” (the extract from a chrysanthemum daisy) group. The most common pyrethroid termiticide today is ‘BIFENTHRIN’, which is the ‘active’ in a brand known as “Biflex”. They are strongly repellant to termites, but virtually odourless to people.

NON-REPELLANT – These are the new generation of termiticides that are not detected by termites, which travel through the treated zone, become contaminated but keep travelling for a while and thereby contaminating many other termites. (Trophollaxis)

‘MAGIC’, NON-REPELLENTS – We see inferences in marketing material that the new generation non-repellent termiticides will, when applied around a building, destroy indirectly a termite colony nest that is located away from the building, such as in a garden tree. The implication is that the trophollaxis effect is so strong that it will kill the entire infesting colony back in the nest, and that treatments do not have to form a continuous treatment zone because the termites will die anyway.

This is a little too convenient has not been the experience of STC, with termite nests located in nearby trees routinely surviving unaffected by a non-repellent termiticide treatment of an infested building. We accept that these new termiticides are highly effective, but they are not magic, and soil treatments should not have gaps in them – it is like leaving the gate open in a paddock.

Which is Best?

REPELLENTS – Bifenthrin. “BIFLEX” Longest lasting (“at least 10 year” label) Best for protecting new and existing buildings that are not under current termite attack.


“Altriset”. (Chlorantraniliprole) Highly effective with best trophollaxis effect. Best against highly aggressive infestations if low toxicity is a priority. Non- toxic. Not on poisons schedule. Expensive. Longevity “Up to 8 years” according to Syngenta’s label.

“Termidor”. (Fipronil) This is a highly effective and very popular insecticide with very strong usage against the aggressive termite attacks in Northern Australia. It has strong trophollaxis effect and soil bonding properties and can be used where there is moisture movement is the soil. It is not taken up by plants but is more toxic than other insecticides. It comes under some criticism based on environmental concerns, especially related to any contamination of waterways. Honey bee colony deaths in Southern NSW have been attributed to Fipronil poisoning.

“Premis”. (Imidacloprid) Has strong trophollaxis effect and is very effective. It is water soluble, and less enduring in wet soils. On the other hand, it will seep through the soil and has better soil penetrating properties. Less toxic. Absorbed by plants and a risk to bees. Banned in France for this reason.

What matters to you?

Your decision will probably be based on a trade-off between longevity, toxicity and cost.

In our experience the choices appear reasonably simple and are as follows:-

  • Lowest Toxicity, heavy infestation- “Altriset”. (Expensive)
  • Very powerful, higher toxicity and strong soil binding- “Termidor” (expensive)
  • Longest lasting, tried and well proven over many years – “Biflex” (Moderate cost)

Australia has one of the most stringent pest control industry regulatory systems in the world. All the termiticides that are proposed to treat your building have undergone thorough evaluation and approval by national and state government authorities. Our company will use these approved termiticides in accordance with all government regulations.

Take precautions

The following commonsense precautions should be observed both before and after your premises are treated:

  1. You should advise us of any pets or any personal or family allergies, or other concerns.
  2. Keep pets confined during treatment, to prevent their escape through an opened door/ gate.
  3. Avoid contact with treated soil until the termiticide has dried.
  4. Observe any verbal advice provided by your termite technician at the time of treatment.
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