Cockroaches Are Rapidly Evolving To Become "Almost Impossible" To Kill With Chemicals


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

Senior Journalist


It's often said that cockroaches could even survive a nuclear apocalypse. Well, soon they might be able to even tolerate insecticides too. Yodchompoo/Shutterstock

The rise of the superbug cockroach is upon us. A new study has found that German cockroaches (Blattella germanica) are rapidly evolving to become resistant to many widely used bug sprays and insecticides, as well as chemicals they've never been directly exposed to, making them near-impossible to eliminate and one step closer to taking over the world. 

Remarkably, the study published in Scientific Reports revealed these scuttling pests could even develop resistance within a single generation. Others also developed cross-resistance, meaning they gained a tolerance to a usually toxic substance just through contact with a similar type of insecticide.  


“We didn’t have a clue that something like that could happen this fast," lead author Michael Scharf, of the Department of Entomology at Purdue University, said in a statement

“We would see resistance increase four- or six-fold in just one generation."

The researchers tested out different treatments of three insecticides – abamectin, boric acid, and thiamethoxam – in numerous cockroach-infested apartments across Indiana and Illinois over six months. In one treatment, three different insecticides were rotated each month for three months and then repeated. In a second, they used two insecticides from different classes for six months. In the third, they chose one insecticide to which cockroaches had low-level starting resistance.

German cockroach feeds on an insecticide in the laboratory at Purdue University study. John Obermeyer/Purdue Entomology

Regardless of the different chemical cocktails, the researchers were unable to reduce the size of the cockroach population. In the single insecticide treatment, populations grew with around 10 percent as individuals starting to evolve resistance. Even with the two insecticide treatments, the cockroach populations actually skyrocketed. The three-pronged attack managed to maintain the number of cockroaches but it was ultimately unable to reduce it.


They later backed up these findings through lab tests. As anticipated, the results showed that a considerable share of the cockroaches and their offspring had become “essentially immune” to a particular class of pesticide.

Cockroaches can pump out up to 50 offspring during their three-month reproductive cycle, so only a small portion of their offspring need to develop cross-resistance, survive, and reproduce for a population to bounce back and boom within a couple of months. 

This order of insect is widely hated for good reason. They are carriers of dozens of nasty pathogens, including E. coli and salmonella, as well as asthma-triggering allergens. They also live exclusively in human environments, so they run the risk of being a vector for disease.

While cockroaches are still not immune to a good stomp of a foot, this new study does suggest that humans need to wise up when it comes to pest control. The researchers say their findings highlight the need for combining chemical treatments with traps, improved sanitation, and vacuums to control cockroaches, rather than just relying on insecticides. 


“This is a previously unrealized challenge in cockroaches,” concluded Scharf. “Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone.”


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