Lead researcher Michael E. Scharf said that the cockroaches' resistance "will make controlling these pests almost impossible with chemicals alone"

By Jen Juneau
July 03, 2019 10:03 AM
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Potential bad news for people who aren’t fans of cockroaches (a.k.a. most): You might need to start incorporating traps to get rid of them — or move to another planet altogether.

A new study out of Purdue University, published last month in Scientific Reports, looked at a group of the German cockroach species which researchers exposed to different types of insecticides over the course of six months. The study found that not only were they able to resist the chemicals, but the bugs also developed immunity. Additionally, the cockroaches can pass that same immunity on to offspring.

The paper explained that the purpose of the study was to address the fact that “insecticide resistance has been a consistent barrier to cockroach control since the 1950s,” noting that the German cockroach “threatens human health by producing asthma-triggering allergens [and] vectoring pathogenic/antibiotic-resistant microbes, and by contributing to unhealthy indoor environments.”

The project’s researchers (Mahsa Fardisi, Ameya D. Gondhalekar, Aaron R. Ashbrook and Michael E. Scharf) then looked at multiple generations of the cockroach to evaluate the evolution surrounding insecticide resistance — and the results were alarming.

“Our findings show clear links between predicted resistance levels and field performance of insecticides, poor efficacy of insecticide deployment strategies on populations with evolved resistance and unexpected selection of field populations for broad cross-resistance across insecticides,” read the study.

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The solution, unfortunately, may no longer be to try different pesticides, as a “cocktail” mix has usually done the trick in the past where exterminators are concerned. This study rotated use of three courses of insecticides, which worked in keeping the cockroaches’ population steady but “was mostly ineffective” at reducing it — pointing to the species’ ability to adapt to the changing chemicals.

Scharf, the lead researcher on the study, said in a statement obtained by CNN that their results displayed “a previously unrealized challenge in cockroaches” and that the insects “developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone.”

He also shared with CNN that female cockroaches can birth up to 300 offspring over the course of their lives and that it was possible for one cockroach generation’s insecticide resistance to increase up to a whopping six-fold.

“We didn’t have a clue that something like that could happen this fast,” Scharf — who also serves as chair and professor in Purdue University’s Department of Entomology — said in a statement, as obtained by Live Science.

Cockroach

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“If you have the ability to test the roaches first and pick an insecticide that has low resistance, that ups the odds,” he added, according to Purdue. “But even then, we had trouble controlling populations.”

Using traps and other elimination methods, Scharf advised, may be the answer as opposed to relying on chemicals alone — a potentially costly mix, especially considering the problem is more prevalent in low-income areas.

“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,” he said in a statement. “Combining several methods will be the most effective way to eliminate cockroaches.”