A new study by researchers at Purdue University in West Lafayette, Ind., found evidence that the German cockroach species is becoming harder to kill as the worldwide pest rapidly develops cross-resistance to multiple types of insecticide at one time. The findings were published in the journal Scientific Reports last month.
“This is a previously unrealized challenge in cockroaches,” the study’s lead author, Michael Scharf, said in a statement on June 25. “Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone.”
The researchers tested three methods of professional-grade insecticides on German cockroaches at multi-unit buildings in Indiana and Illinois over a six-month period in 2016. First, they rotated between three different insecticides each month for three months and then repeated.
Second, they used a mixture of two insecticides sprayed monthly. Lastly, they used a single treatment — abamectin gel bait — once a month in an area where cockroaches showed a low resistance to abamectin.