As we prepare to enter the Summer bedbug season, evolutionary biology Ph.D. and science writer Amy Maxmen offers several useful facts about everybody's favorite blood-drinking mattress dwellers. Her number one recommendation: If you have a bedbug problem, call a professional to deal with it. Bedbugs aren't something to try killing on your own.
During the last 50 years, bedbugs have largely become biologically resistant to the pesticides sold at your corner store, namely pyrethroids and pyrethrins. DDT falls into the pyrethroid group, shedding doubts on claims that lifting the EPA's ban on this dangerous chemical would curb the current bedbug resurgence. Spraying pyrethroids or pyrethrins directly on a resistant bedbug at close range may in fact kill the pest, but there's little chance of hitting each individual insect, as armies of the sesame-seed sized bugs hide in the teeniest crevices.
"Hair spray, Windex, spearmint or eucalyptus oil will kill bedbugs at a close range too," says Coby Schal, an urban entomologist at North Carolina State University in Raleigh. "But I'm not advocating those approaches because bedbugs can walk right over these sprays." Although the insect repellent DEET is not a pyrethroid or pyrethrin, Schal says it won't deter a starving bed bug from seeking out human blood. Instead, repellants and sprays encourage the bugs to explore unsprayed territory, like your living room or your neighbor's flat.
Pesticide resistance provides tremendous evidence for evolution by natural selection. A mutation in a gene encoding a protein in bedbugs' nerve cells allows the cells to resist the lethal damage inflicted by pyrethroid and pyrethrins. With each spray, bedbugs with the mutation out-live their non-resistant pals and survive to produce resistant offspring. Incidentally, cockroaches have mutations in this protein too. If it weren't for poisoned bait, we might have a hefty cockroach problem on our hands, says Schal. At the moment, he is studying what attracts bedbugs to human blood. If this compound can be identified and mimicked, bedbugs might be baited too.
Worse yet, misuse of these sprays may lead to digestive problems, skin irritation, and may worsen asthma and allergies (1). "People think if you can buy a pesticide at a supermarket it can't be dangerous, so they use them like mad when in fact almost none of these chemicals have been tested on humans," says Stephanie Chalupka, an environmental and occupational health expert in Massachusetts at Worcester State College and Harvard School of Public Health in Boston. "I think the public health community could do a better job of getting out information on what is useful and safe, and what may put kids at risk." Chalupka says she's particularly concerned for pregnant women and their developing babies. "All sorts of compounds can get to the developing fetus, which is at a very vulnerable state as its organs and systems are forming."
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.