When properties are challenged by termites pest managers are constantly faced with a need to know construction methods from yesteryear through to the modern day. On older homes the replacement of the outside loo may give termites access whereas determining the type of concrete slab is critical in planning treatment of modern homes.
Some damage, such as drilling through water pipes or breakages are known immediately but it is the ‘surprise phone call’ from a customer saying that your treatment has caused damage that sends shivers down the spine.
An understanding of wall and timber finishes is a requirement when spraying surfaces, especially indoors. Most of us are aware of the need to take great care when spraying indoors. Even clean water may leave marks if it is allowed to run down the wall or cause drops on the ceiling.
My first taste of that unpleasantness was thirty years ago and involved a $20,000 persian rug The customer had 6 or 7 of these rugs and wanted to protect them from damage. I quoted and determined that we would use a light mist of a wettable powder product (that was before suspension concentrates). One of my technicians treated the rugs and a few days later the customer phoned saying the colours had run in one of the rugs. In short, the technician had treated this rug and then rolled it up (still moist) because there was not enough space on the floor for it to dry. Obviously not the action of the chemical but the treatment process.
Another case of ‘damage’ was unusual. As a company rep I investigated white dots left by a new product on kitchen lino. When the pest manager looked at the floor he had just treated – his first use of the product – he was distraught but the lady of the house was not concerned. For years she had waxed the kitchen floor weekly with ‘One-go Floor Wax’. Whenever a drop of water contacted the waxy floor the lino turned white, then cleared when it dried.
Emulsifiable concentrate products contain solvents and emulsifiers and are then diluted with water. These chemicals may react with the surface of some paints. I was asked to look at a ‘streaking’ complaint on a rendered house near the ocean. The ‘streaks’ appeared to be the same colour as the paint residue on the paint tin as though the chemical had cleaned the render.
Wettable powders and suspension concentrate formulations can leave visible residues on dark surfaces. These can be cleaned up with warm soapy water.
However water itself can damage surfaces even when runs or drips. Garrards Pest Review March 2000 reported discolouration where a cockroach treatment bleached a paint when water reacted with a lime-based mottle effect paint. Freshly painted surfaces are also susceptible to showing spray damage.
Care must be taken when treating historic homes. Shellac replaced oil and wax finishes in the 1800s and became the dominant timber finish until it was replaced by lacquer in the 1920s. Shellac is obtained by scraping resin flakes secreted by the female lac bug on trees in India and Thailand. Shellac has been used as a primer, odour-blocker, insulator and making 78-rpm phonograph records.
Shellac is not waterproof and may be protected oiled to protect the timber. Applying water to timber stained with shellac may cause white marks as the water reacts with the water-sensitive timber or the protecting oil. Where this has caused marking an application of oil may remove the marks.
Wherever you apply a liquid treatment take a few moments to consider if the application may cause damage.