Troubling news from the front of the war on bugs: Scientists have found the overuse of certain insecticides against bed bugs has led to an increased resistance to the compounds, making them much less effective than advertised.

One of the most of the most widely used commercial chemicals to kill bed bugs are not effective because the insects have built up a tolerance to them, according to a team of researchers from Virginia Tech and New Mexico State University.

Millions of dollars are spent each year on insecticides to kill the bugs that have wreaked havoc on everything from hotels in New York City to homes in Los Angeles. But the new study suggests those efforts have been counterproductive, making the chemicals less effective than alternative methods, such as steaming and using barriers.

"While we all want a powerful tool to fight bed bug infestations, what we are using as a chemical intervention is not working as effectively it was designed and, in turn, people are spending a lot of money on products that aren't working," said Troy Anderson, an assistant professor of entomology in the Virginia Tech College of Agriculture and Life Sciences.

Anderson and Alvaro Romero, an assistant professor of entomology at New Mexico State University, published their findings in the Journal of Medical Entomology.

They examined the class of insecticides called neonicotinoids, or neonics, which is often paired with pyrethroids in commercial applications to treat bedbugs.

"Companies need to be vigilant for hints of declining performance of products that contain neonicotinoids," Romero said. "For example, bedbugs persisting on previously treated surfaces might be an indication of resistance."

The researchers conducted their study by comparing bedbugs from homes in Cincinnati and Michigan that had been exposed to neonics. They also examined pyrethroid-resistant bugs from New Jersey that had not been exposed to neonics since they were collected in 2008.

The bedbugs \that never have been exposed to neonics died when they were exposed to a very small amount of the insecticide. The New Jersey bedbugs fared slightly better, showing moderate resistance to four different types of neonics.

But the bedbugs from Michigan and Cincinnati, which were collected after combinations of insecticides were introduced to the U.S., had much higher levels of resistance to neonics.

"Unfortunately, the insecticides we were hoping would help solve some of our bed bug problems are no longer as effective as they used to be, so we need to reevaluate some of our strategies for fighting them," said Anderson, who is also a researcher at the Fralin Life Science Institute.

"If resistance is detected, products with different modes of action need to be considered, along with the use of non-chemical methods," said Romero.