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'Nothing' Works Well When It Comes to Killing Cockroaches

Researchers found the bugs rapidly developed resistance
By Kate Seamons,  Newser Staff
Posted Jul 3, 2019 7:56 AM CDT
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."You're left with survivors, no matter what."   (Getty Images)

(Newser) – If cockroaches gross you out, you are not going to be a fan of this study. New research out of Purdue University has found the most common type of cockroach is getting "closer to invincibility," as a press release puts it. This after researchers tried, and mostly failed, to vanquish the German cockroach from two low-rise multi-housing units in Indiana and Illinois. They used three different methods involving insecticides: rotation, mixture, and a single application. Purdue professor Michael E. Scharf tells USA Today they wanted to test "ideas that had been out there for a long time," thinking one of them would work, as they're the methods exterminators rely on. "It turns out, nothing worked really well," he says. And the researchers started with an advantage: They trapped the cockroaches and tested them to see which insecticides they had the least resistance to and used those in the six-month test.

In the first case, three insecticides were used one at a time for a month each, then repeated; the population neither grew nor decreased. In the second, a combination of two insecticides was used, and the bugs multiplied. The only success came in the single-insecticide experiment, but even that had its limitations: One single application worked, but in another, in which the cockroaches had 10% resistance to the insecticide used, their numbers grew. The researchers found the resistance the bugs developed to one insecticide would give them resistance against ones they hadn't even been exposed to yet due to the similar nature of the insecticides. An ominous quote from Scharf: "We would see resistance increase four- or six-fold in just one generation. We didn't have a clue that something like that could happen this fast." Among his best recommendations? Empty your trash daily. (Read more cockroaches stories.)

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