[University Research] University of Kentucky: Bed Bugs Exhibit Resistance to Pyrethroids

Entomologists at the University of Kentucky in Lexington report that some bed bug populations across the United States are resistant to pyrethroid insecticides.

Alvaro Romero, a doctoral student, and his co-investigators, Kenneth Haynes (project leader), Michael Potter and Daniel Potter, found that adult bed bugs from four infestations collected from separate locations in Kentucky and Ohio were several thousand-fold resistant to deltamethrin and lambda-cyhalothrin compared to a susceptible laboratory strain. This high level of resistance may compromise the efficacy of insecticidal products that have pyrethroids as an active ingredient, UK reports.

Using a discriminating dose test with bed bug nymphs, the researchers further found that seven out of the eight field populations submitted by pest management firms across the country were well over 100-fold resistant to deltamethrin. These tests included bed bugs originating from California, Florida, Kentucky, Ohio and Virginia. Details of the study will be reported at NPMA’s PestWorld convention in Grapevine, Texas, this month.

While the results suggest that resistance to pyrethroids is becoming more widespread, the investigators emphasize that it is not yet universal and many firms are still reporting good control with these active ingredients.

"We have to be careful that the whole resistance issue doesn’t get blown out of proportion and all of the sudden everybody is saying, ‘We can’t kill bed bugs.’ We don’t know that yet," said Rick Cooper, technical director, Cooper Pest Solutions, Lawrenceville, N.J. "Resistance is something to be concerned about, but we don’t know how widespread it is."

According to the University of Kentucky, the findings are significant because the cancellation of most carbamate and organophosphate insecticides has left the industry with few effective alternatives.

Bed bug resistance to insecticides is not a new phenomenon. Resistance to DDT was first reported in the late-1940s and was so widespread a decade later that other products were already being recommended as alternatives. UK Extension Entomologist Michael Potter cautions that there are a number of reasons other than insecticide resistance why pest control professionals may have difficulty eliminating bed bugs.

Cooper agreed. "Resistance is like the world’s biggest crutch and we watched it with roaches for years," he said. "We know that most of the time when we realize control failure with roaches it has nothing to do with resistance, it has to do with individual performance. Look in the mirror and you’re usually going to see the problem. You didn’t do the job well enough." The same will probably hold true for bed bugs, he said.

However, resistance may represent a major challenge to the management of bed bugs and may accelerate the need for alternative tactics, UK reports. Pyrethroid resistance is likely a factor in the resurgence of this international problem, Haynes said.

"Insecticide resistance has occurred in the past and it will occur in the future," said Steve Burt, managing director, Professional Pest Management, Bayer Environmental Science. "As we’ve learned in the past, if you use insecticides properly and in rotation, you won’t have a problem. The key is all of us need to be good stewards of the products we have at our disposal, whether that be the PCO, the distributor or the manufacturer."

Editor’s note: Photos are courtesy of Mike Potter.