A new study brings bad news for people fighting bedbug infestations and companies that sell over-the-counter insecticides.

Ohio State University entomologists Susan Jones and Joshua Bryant found that "bug bombs" and "foggers" — cheap, insecticide-spraying aerosols that have been marketed for decades as do-it-yourself alternatives to exterminators — were ineffective against even the most vulnerable of bedbugs.

In the study, published last month in the Journal of Economic Entomology, the researchers tested three popular commercial foggers against five wild strains of bedbugs found in Ohio homes and one laboratory strain that had not been exposed to insecticides.

They found that after spraying the bugs with a typical two-hour fog, only the laboratory bugs had died; nearly all of the wild bedbugs, though placed in completely exposed containers, had survived. When the scientists covered the containers with paper to simulate the bedding that the insects often nest in, nearly all the bedbugs from every strain survived — even the laboratory strain.

The scientists concluded not only that most wild bedbugs are resistant to pyrethroids, the active ingredients in fogger aerosols, but also that the fogging process itself is fundamentally flawed.

"The spray can't penetrate through a thin paper sheet, much less into cracks and crevices where bedbugs hide in real life. On top of that, we're dealing with bugs resistant to pyrethroids in the first place" said Jones. "It's a death knell for this type of product."

Jones, who had initially designed the study to test whether foggers caused surviving bedbugs to scatter and inhabit previously uninfested areas, said the results were so unexpectedly poor that she had to backtrack and ask whether these products worked at all.

"After we ran the first spraying experiments, we saw that the bugs were crawling around as if nothing had happened,'" she said.

The study tested two general-use products, Spectracide Bug Stop Indoor Fogger and Eliminator Indoor Fogger, and one marketed specifically for bedbugs, called the Hot Shot Bedbug and Flea Fogger. All three were developed by Spectrum Brands.

Missy Henriksen, a spokeswoman at the National Pest Management Association, said that Jones and Bryant's results "could be new for consumers but weren't a surprise to the professional pest-management industry."

University of Kentucky entomologist Kenneth Haynes, who wasn't involved in the study, said that academics have not held stock in foggers for years.

"I don't view bedbugs as a do-it-yourself project, and I'd call an exterminator if I had them — even though I know quite a lot about the bugs," Haynes said.

Asked for comment, Spectrum provided an email statement saying that the Hot Shot fogger "has been thoroughly tested and is proven to be effective against the bedbugs they contact."

Bedbug infestations have been on the rise since the ban of DDT in 1972, due in part to increased international travel and the evolution of bedbug resistance to weaker insecticides. The bugs can be dragged into homes and offices on clothing, luggage, used furniture and pets — especially after trips to summer camps or foreign countries.

Once they arrive, adult bedbugs can survive for more than half a year without feeding on blood from a human or other warm-blooded animal.

"That's bedbug biology. They have evolved to be very good at hiding and waiting to home in on the next blood meal," Henriksen said.

Haynes said that foggers, in addition to fueling increased bedbug resistance to insecticides, can pose dangers to people.

In 2008, the Centers for Disease Control and Prevention reported 466 cases of acute, pesticide-related illness or injury associated with exposure to foggers between 2001 and 2006 in eight states. The study noted that harm often occurs when users leave fogged rooms too late, re-enter too early, don't wipe down sprayed surfaces or use flame nearby. (Pyrethroids are extremely flammable.)

Jones said she hoped the Environmental Protection Agency would review manufacturers' efficacy data about these products and investigate which bedbug strains were used to test their products.

For consumers, she said that a sharp eye around the house and a habit of running linens in the high heat dryer cycle are far more effective at keeping the unwelcome critters at bay than foggers are.