Cockroaches will soon be ‘almost impossible’ to kill with chemicals, researchers say

Cockroaches are becoming immune to insecticides

Cockroaches are becoming immune to insecticides

These insects pose a real threat to human health.

The bugs are so risky because they are carriers of dozens of bacteria, including E. coli and salmonella, which can make people very sick.

"This is a previously unrealized challenge in cockroaches", commented Michael Scharf, a professor in the Department of Entomology, who led the six-month-long study and whose findings have now been published in the journal Scientific Reports.

Cockroaches develop resistance to several classes of insecticides at a time, making the fight against these insects nearly impossible with only chemicals.

The study was conducted in various buildings in central IL and in in the U.S. as well as at Purdue University's labs that had roach infestations.

In the first test, three types of insecticide were rotated for three months, before the process was repeated. In a second, they used a mixture of two insecticides of different classes for six months.

The problem was found to get worse in the areas where a number of different insecticides were used due to the bugs developing cross-resistance.

In each location, cockroaches were captured before the study and tested in the laboratory to determine the most effective insecticides for each treatment, allowing scientists to achieve the best results. "But even then, we had trouble controlling populations".

The scientists studied cockroaches in apartment buildings in IN and IL for six months, rotating various treatments of insecticides, according to a news release.

In addition, the mixture of two insecticides did not work and populations flourished.

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One of the single-insecticide experiments suggested the population was at first vulnerable to the method, and in that case they were able to mostly wipe them out. In another, there was about 10% resistance initially, and populations eventually increased.

Lab tests of the cockroaches found that cross-resistance likely played a significant role in cockroaches that survived treatments, the release states. A certain percentage of cockroaches showed resistance to a class of pesticides.

According to Scharf, not only would roaches that survived a treatment be "essentially immune" to that type of insecticide class in the future-their offspring would be too.

Some cockroaches are even becoming resistant to poisons they haven't even been exposed to yet.

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".

The difficulty in containing population numbers is amplified by the fact that females can have up to 50 offspring during a three-month reproductive cycle.

Scharf noted: "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".

'Combining several methods will be the most effective way to eliminate cockroaches'.

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