Cockroaches Have Become Even Harder To Kill, Study Finds

The German cockroach is described in the report as “the species that gives all other cockroaches a bad name

The German cockroach is described in the report as “the species that gives all other cockroaches a bad name

These insects pose a real threat to human health.

The researchers weren't fucking around - they tested three different insecticides on roach populations in four apartment buildings over a period of six months, with one group of cockies exposed to a single insecticide, another two insecticides from different classes and the third with three insecticides.

Even if a small number of cockroach offspring developed a resistance to a particular insecticide, numerous newborn bugs could develop a cross-resistance in which a population that is eliminated in a single "treatment" could explode again in mere months.

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

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.

Each class of insecticide acts in a different way to kill cockroaches.

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.

"If you have the opportunity to test cockroaches before and choose an insecticide that has low resistance, it increases the chances", says Michael Scharf. In another single-insecticide experiment, a population with only 10 percent starting resistance actually grew.

Lab tests of the cockroaches found that cross-resistance likely played a significant role in cockroaches that survived treatments, the release states.

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.

However, he said this resistance is going to appear in Australia sooner or later, either by mutations occurring in German cockroaches on Australian soil or by being bred into the population from transient cockroaches arriving in shipping containers.

We have seen the resistance quadruple or sixfold in a single generation.

The Purdue researchers found that certain cockroaches who had mutated to be resistant to particular classes of pesticides were quickly passing those traits on.

According to the researchers, female cockroaches have a three-month reproductive cycle during which they can have up to 50 offspring.

"We didn't have a clue that something like that could happen this fast".

Scharf recommended a combination of chemical treatments, traps, improved sanitation and vacuums as the most effective way of removing the pests - for now.

"These techniques are often more expensive than using insecticides, but if they do not control or eliminate a population, then money is wasted", says Scharf.

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

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