How they attack your home
Queensland in general has a varied past in terms of what was required to protect new dwellings from termites. The law has changed several times over the years, affecting what sort of treatment your home would have received during its construction. The type of house you have may also determine what sort of protection was carried out, if any.
The oldest residential homes in Brisbane, in inner city suburbs, mostly pre-date chemical treatment. These houses mostly rely on physical protection in the form of termite shields or “ant caps”. In many cases the old termite shielding has corroded after years of service and no longer provides adequate protection. Termite shields often rust around the connection point, meaning that an ‘ant cap’ over a timber pier that looks fine visually may be compromised in the middle where you can’t see. Often builders nailed the ant caps on and after time the nails rusted out providing undetected entry points from the middle of the wood stump into the house.
The discovery of the insecticidal applications for DDT and the organochlorine family of chemicals in 1939 led to the widespread use of them as termiticides post-war. These chemicals were VERY effective, due to their ease of use and ability to move through soil and eventually pre-construction spraying with this group became a widespread practice. Heptachlor, Dieldrin, Aldrin, Aldrex, Chlordane and several others were used almost exclusively up until July 1995 when their use was banned. Sprays of this generation were given a life expectancy of 10-15 years, not 40 years as is commonly mentioned.
There were several issues that arose that resulted in these chemicals being banned. They were exceptionally long lived; this ultimately proved to be a bad thing as they did not remain where they were applied. Instead they moved into the biosphere, building up in top predators such as fish, birds and humans. Also, the organochlorine group proved to be carcinogenic without exception.
After July 1995, underslab spraying continued with a new generation of chemicals; synthetic pyrethroids such as bifenthrin or organophosphates such as chlorpyrifos. These chemicals were chosen as they had relatively short life expectancies, compared to the organochlorins, which minimised their environmental impact. Poor application practices of the new products during those times left some buildings grossly under protected. Another issue which affected this form of termite protection in newly built homes was the practice of laying irrigation pipes and bark chip over and through the treated soil protection zones.
As a result, the law was changed again, effective in late 2000. All new homes or renovations were required to be built with physical protection that must either be durable or able to be replenished for 50 years. With correct installation, modern systems have greatly reduced termite attacks but these houses still require annual termite inspections.
Right through this whole era, arsenic dust was used to treat active termites in houses in the form of ‘dusting’. Iron oxide was added to colour the powder, old arsenic dust marks will appear pink or red and full protective gear must be worn when removing contaminated timber. Never wet arsenic marks, the chemical can react changing from Arsenic Trioxide to Arsenic Pentoxide, a water soluble and equally toxic product. For this reason Arsenic was never used in trees; its use would kill the tree.
Modern chemicals, such as fipronil (Termidor) and imidacloprid (Premise and Confidor) have greatly reduced the risk to people and their pets but are still capable of damage when misused. Thankfully they are far more effective termiticides than some of their predecessors.