Q. Why have bedbugs become such a problem? Are there any new ways to attack them?

A. Scientists believe that bedbugs have developed resistance to some insecticides, and travel is helping to spread the resistant insects worldwide.

Another major contributor is the failure of many hotels and residential landlords to identify infestations promptly, and to dispose of or treat infested bedding and carpeting.

It has been known since the 1950s that bed bugs can develop resistance to commonly used insecticides, like pyrethrin. Resistance has emerged to more products over the years.

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The biological mechanisms include a thickening of the bedbugs’ exterior cuticle, so that an insecticide does not penetrate properly, and metabolic resistance, in which the insects produce extra amounts of detoxification enzymes.