Cockroaches are evolving and becoming almost impossible to kill with chemicals, US scientists announced.

A study by Purdue University shows that the reason for this is that cockroaches build immunity when they survive an insecticide treatment. Therefore, passing the acquired immunity to their offspring.

The study also showed that these evolving cockroaches gain immunity from other insecticides that they probably have never even been exposed to. This is scientifically called ‘cross-resistance’.

“We would see resistance increase four- or six-fold in just one generation,” Michael Scharf, professor and O.W. Rollins/Orkin Chair in the Department of Entomology said. “We didn’t have a clue that something like that could happen this fast.”

“Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone,” said Professor Scharf.