In the US, consumer bug spray is regulated by the Environmental Protection Agency and manufacturers must show they are 90 percent effective to pass muster. But while these insecticides may kill German cockroaches born in the laboratory, your can of grocery bug spray is no threat to the real world roaches in your pantry.
University of Florida entomologist Johnalyn Gordon and colleagues demonstrated that consumer bug sprays are ineffective on infestations because the cockroaches have developed resistance to the key ingredient, a group of pesticides called pyrethroids.
From New Scientist:
The products are designed to be sprayed on to surfaces, killing the insects when they walk over the coating. But in the team's tests, coated surfaces killed fewer than 20 per cent of the collected cockroaches after exposure for 20 minutes. "Even directly spraying them in an enclosed container with these products, we weren't getting 100 per cent mortality," says Gordon.
When the cockroaches were forced to remain on the treated surfaces, most of the products took between 8 and 24 hours to kill. Previous research has shown that these insects avoid lingering on surfaces treated with pyrethroids, making it unlikely this would happen in reality.
Manufacturers should test bug sprays on recently collected specimens, Gordon says. For now, she adds, your best bet is cockroach baits.
