When we tested cockroach killers in 1999 and 2004 we found that the same active ingredients (second and third-generation pyrethroid insecticides) that were tested in 1999 were less effective in the 2004 test at the three-month mark. We will be revisiting the current crop of surface sprays at the three month mark to see whether this pattern is repeated.
Why do active ingredients lose their long-term effectiveness?
According to our expert lab, a likely explanation is that the cockroaches have developed resistance to the older second and third-generation pyrethroid insecticides.
The development of insecticide resistance in the German species is well documented. In fact, chlordane-resistant German roaches were identified as far back as the early 1950s, and resistance to all major groups of insecticides has now been reported in various roach populations around the world.
Other insects, such as malaria-carrying mosquitos, have also developed resistance to various insecticides. And they’re not the only examples of resistant bugs posing a threat to humans or valuable crops.
Experts caution that the responsible use of insecticides is an important factor in controlling the development of insecticide resistance. For cockroaches, this means the integrated approach — not overusing insecticides and also taking into account good hygiene and cockroach habits.
Value for money?
Same product, different price tag
The two major supermarkets make much of their own home brands, and in particular their “luxury” home brands such as Woolworths Select and You’ll Love Coles. CHOICE was staggered to discover that two of the products on test, Home Brand Insect Spray Low Irritant and Woolworths Select Low Irritant Insect Spray, have identical active ingredients in identical quantities, but the luxury brand is twice as expensive per 100 grams and comes in a smaller container. To add insult to injury, both also have below-average performance, taking over 10 minutes to kill our samples of the larger American cockroach.
Bigger not always better
Occasionally we see larger one or two litre packs of cockroach killers which often don't come with a propellant but rely on you to pump the product out of the container. The larger pack can give the illusion of getting more for your dollar.
If you’re tempted to try one of these DIY surface spray pack options, such as the Mortein Do-It-Yourself Professional Indoor Surface Spray or Hovex 2 in 1 Outdoor & Indoor Surface Spray; the Mortein is more expensive than the Atlas equal top rating surface spray, and the Hovex 2 in 1 Outdoor & Indoor Surface Spray is less effective than some of the cheaper can options.