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.
A Purdue University study led by Michael Scharf, professor and O.W. Rollins/Orkin Chair in the Department of Entomology, now finds evidence that German cockroaches (Blattella germanica L.) are becoming more difficult to eliminate as they develop cross-resistance to exterminators' best insecticides.
"Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone."
In each location, cockroaches were captured before the study and lab-tested to determine the most effective insecticides for each treatment, setting up the scientists for the best possible outcomes.
In one of the single-insecticide experiments, Scharf and colleagues found that there was little starting resistance to the chosen insecticide, and they were able to all but eliminate the cockroach population.
If even a small percentage of cockroaches is resistant to an insecticide, and those cockroaches gain cross-resistance, a population knocked down by a single treatment could explode again within months.
Rapid evolutionary responses to insecticide resistance management interventions by the German cockroach (Blattella germanica L.), Scientific Reports (2019).