'Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests nearly impossible with chemicals alone'. Many roaches can carry dozens of bacteria including E. coli and salmonella, leaving behind traces of feces, saliva and body parts that can cause serious health problems for many.
A German cockroach feeds on an insecticide in the laboratory portion of a Purdue University study that determined the insects are gaining cross-resistance to multiple insecticides at one time.
With the two-insecticide mixture, the pests even appeared to thrive. This means even a small number of insecticide-resistant cockroaches could quickly spell trouble.
Peters notes US populations of German cockroaches appear to have different resistance to those in Australia and, for the moment at least, Australian cockroaches are still able to be killed by traditional insecticides.
In one experiment with a single insecticide, Scharf and his colleagues found that there was little resistance to the insecticide chosen, and they were able to virtually eliminate the insect population. But, in another trial with 10 percent starting resistance, the population grew despite treatment.
Lab tests of the cockroaches found that cross-resistance likely played a significant role in cockroaches that survived treatments, the release states. In fact, those who survived treatment and their offspring would be essentially immune to this insecticide in the future. They also gained resistance to other types of insecticide, too, even types that they hadn't yet been exposed to, researchers said.
The research paper is titled "Rapid evolutionary responses to insecticide resistance management interventions by the German cockroach".
We have seen the resistance quadruple or sixfold in a single generation.
'We didn't have a clue that something like that could happen this fast'.
According to the researchers, female cockroaches have a three-month reproductive cycle during which they can have up to 50 offspring.
Throughout the six-month-long study, scientists found the cockroach population either remained stable or actually increased, with resistance to various insecticides being passed down to offspring. They recommend combining chemical treatments with traps, vacuum cleaners, but also improved sanitation facilities.
'Some of these methods are more expensive than using only insecticides, but if those insecticides aren't going to control or eliminate a population, you're just throwing money away, ' Scharf said.
"Combining several methods will soon be the only effective way to eliminate cockroaches", concludes Michael Scharf.