How Bed Bugs Resist Pesticides

December 1, 2015 | Sandra Kraft and Larry Pinto

As PMPs battle this hard-to-control pest, researchers are working overtime to determine why some populations develop resistance.

Resistance is a constant concern for PMPs, whether they’re battling German cockroaches, bed bugs or fleas. Fortunately, researchers are pro-actively addressing resistance problems, particularly with bed bugs. What follows is a review of university research efforts relating to bed bug-related resistance throughout the United States.

Genes keep insecticides from entering the bed bug’s cuticle.

Fang Zhu’s research team from Washington State University and the University of Kentucky sorted through the entire bed bug genome looking for genes responsible for insecticide resistance. They found 14 genes and combinations that help bed bugs survive treatment with pyrethroid-type insecticides.

The researchers found most of the genes responsible for pesticide resistance in the bed bug’s cuticle or outer shell. Since bed bugs are so flattened, their cuticle area is huge, providing a large area where pesticides can enter their bodies. Some genes in a bed bug’s cuticle produce substances that actually disable insecticides, making them harmless. Other genes are responsible for pumping insecticides back out of the cuticle before they can enter the bed bug’s body. Besides this first line of defense at the outer surface, bed bugs have other genes that prevent insecticides from attacking their nervous system.

Zhu says that development of new bed bug insecticides should concentrate on finding ways to shut down or mute the genes that help bed bugs resist insecticides. But new pesticides alone will not be enough since bed bugs in the laboratory that are exposed to lethal doses of pyrethroids begin to develop resistance in just a few generations — less than a year. Careful use of insecticides must be combined with other integrated control measures to overcome resistance (Scientific Reports, March 2013).

Do recently fed bed bugs resist insecticides better?

University of California-Riverside researchers Dong-Hwan Choe and Kathleen Campbell tested to determine bed bugs’ susceptibility to insecticides after they had been recently fed. They exposed both fed and unfed bed bugs to deltamethrin, chlorfenapyr and an imidacloprid-cyfluthrin combination. The bed bugs that had just taken a blood meal had delayed mortality to chlorfenapyr compared to the unfed bugs, but not to deltamethrin or the combo. Fed bugs were able to survive significantly longer than the starved bed bugs initially, but by the end of the 10-day test period, mortalities for both groups were similarly high.

How does this affect you? If a fed female bed bug is initially unaffected by your treatment, she has some time to continue laying eggs before she succumbs. If you know the bed bugs in your account have been feeding, you may see a delayed response to your treatment. Your customers may continue to get bitten for a time and you may find eggs hatching after you think an account is free of bed begs. When using chlorfenapyr, treatment of an account that has been vacant for a few days beforehand will likely be more successful than treatment where bed bugs are still feeding (Journal of Economic Entomology, June 2014).