Vegans kill cockroaches

Cockroaches: why poison will soon no longer help against cockroaches

by Peter Carstens
Cockroaches are annoying, potentially harmful to health - and tough. They even develop resistance to poison. And much faster than expected

Cockroaches, also known as cockroaches, have always been considered to be extreme survivors. They can tolerate about ten times more radioactive radiation than humans. (The fact that they would - in contrast to mammals - survive a nuclear war themselves, however, belongs more to the realm of myth.) Even poison is apparently indifferent to some of the evolutionarily ancient six-legged creatures. Since the 1950s there have been increasing reports that insects are becoming increasingly resistant to commercially available insecticides.

This problem could get worse in the future. US researchers write in a recent study that cockroaches could soon be immune to any kind of chemical insect control.

The "chemical club" doesn't always hit

For their investigations, the researchers at Purdue University in the US state of Indiana examined one of the most common species in the US and Europe: Blattella germanica, the German cockroach, which can grow up to 15 millimeters - without a feeler. For six months they tested the effects of various exterminator strategies in two residential complexes: a single active ingredient, a mix and the alternating use of three different active ingredients.

The result: With the "rotation" method, the researchers were able to keep the population stable. The two-active ingredient mix didn't work at all - the cockroach family even grew. In the third application with a single active ingredient, it was found that up to ten percent of the cockroaches survived. Later laboratory tests produced a worrying finding:

Multiple resistances within a generation

Cockroaches that were resistant to one active ingredient developed resistance to substances from other active ingredient classes within a very short time, a so-called cross-resistance. The surviving animals can rebuild large populations within a few months.

"We have observed a four to six-fold increase in resistance within a generation," says entomologist and lead author of the study, Michael Scharf. "We had no idea that something like this could happen so quickly." Cockroaches with such cross-resistance could make it impossible to fight them with chemicals alone.

Cockroaches love to be close to people

Cockroaches are originally at home in the tropics. The German cockroach, however, only lives near people - and likes it warm and humid. It can quickly become a problem - undetected - in restaurants, shopping centers or on ships. Because a single cockroach can arithmetically build up a population of many millions of animals within a single year. Control is required in any case: cockroaches can transmit germs and cause allergies.

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