Besides being gross, cockroaches can cause allergies and spread pathogens within a home. To combat such infestations, residents who can’t afford professional fumigation often turn to bug bombs—canisters sold in stores that release a plume of pesticides.
These products, however, are completely ineffective at controlling cockroach populations and may unnecessarily expose people to insecticides, according to a new study from North Carolina State University (BMC Public Health 2019, DOI: 10.1186/s12889-018-6371-z).
The researchers recruited 30 homes in which at least 50 roaches were caught before the experiment and then treated the homes with various brands of either bug bombs or gel bait traps, which use a food bait to get roaches to pick up insecticides. After one month, they found no difference in cockroach numbers in the homes treated with bug bombs, while roach numbers dropped by as much as 90% in homes with bait traps.
“It’s an excellent and important study confirming what many of us who work in pest control have believed for some time,” says entomologist Michael F. Potter of the University of Kentucky.
For decades, researchers have seen cockroaches develop resistance to pyrethroids (example shown), the class of pesticides released by bug bombs. To probe roaches’ tolerance to the compounds, the team placed two cages of cockroaches, one with lab-raised roaches and one with those caught in the same home earlier, within close range of a bomb. While all of the laboratory roaches died, about 60% of the wild ones survived.
Bug bombs have another problem: their pesticides settle onto horizontal surfaces, whereas roaches typically crawl underneath appliances or vertically on walls.
The bombs also raise safety concerns. They spread propellants, which have started fires when stove pilot lights were left on in a treated home. Also, human health risks from chronic exposure to pyrethroids are still up for debate. “To justify any risk, there’s got to be some benefit,” says the study’s lead author, Zachary C. DeVries. But with bug bombs, he says, there are none.