Rubbing alcohol and mothballs are unlikely to rid your home of bedbugs. (Bigstock)

As bedbugs become more resistant to various pesticides, other defenses are growing in importance. But new tests give low grades to several homespun methods of bedbug defense.

Rubbing alcohol is often recommended for killing bedbugs, for example. But spraying a group of the insects with it left about half alive four days later, Changlu Wang reported at this month’s Entomology 2013 conference. His research team at Rutgers University also found that mothballs failed to wipe out bedbugs after seven days in a plastic bag full of infested clothes. Eggs and immature bedbugs survived the mothball treatment well, and only 44 to 60 percent of the adult males died.

In spite of these and other underwhelming test results, Wang encourages no-pesticide, DIY tactics.

The common bedbug (Cimex lectularius), for decades so rare in the United States that many entomologists had never seen a wild one, has had a resurgence in homes, hotels, planes, ambulances and offices. People’s watchful eyes and mindful habits are the best ways of preventing infestations or stopping them early. And since bug populations are growing increasingly resistant, pesticides that are still in use, especially those available without a professional license, may not help.

Dini Miller of Virginia Tech, analyzing bedbugs’ growing resistance to pesticides, said that among the bugs’ defenses are variations in enzymes that can detoxify certain pesticides and an enhanced outer cuticle that reduces pesticides’ penetration. Miller has found that bug populations combine such defenses, creating a formidable mix.

Bringing back DDT, a fantasy that Miller said she often hears from people fighting infestations, won’t help, because bedbugs demonstrated decades ago that they develop resistance to it. That insecticide was banned in the United States for agricultural use in 1972.

A commercial blend of essential oils turned out to have a major drawback under likely real-world conditions. In a lab where bugs had no chance to bite anybody, treatment with the product Bed Bug Fix had killed 92 percent of bugs by the end of two weeks. But when researchers sprayed bugs and then allowed them to feed, as they might in a home, the insects survived. Just why isn’t clear, Wang says.

Ultrasonic bedbug-repelling devices are popular, but they don’t work, Wang said. In a survey of 23 places infested with bedbugs, five had an ultrasonic repeller.

Based on his research, Wang does support some tools and stratagems for a home campaign against bedbugs. He recommended using bug-blocking mattress casings, washing clothes in hot water and drying them at high temperatures, and, if people have access to the equipment, steaming mattresses and other surfaces. He has also had good results testing dry ice in a big plastic bag as a low-cost fumigation chamber for toys and other hard-to-launder items. He is concerned, however, that people might hurt themselves if they handle dry ice improperly.

His talk inspired discussions among bedbug entomologists about vacuuming to reduce populations of bedbugs. “There are things you can’t steam,” said Mark Goodman of the University of Kentucky. However, others pointed out that vacuuming can make things worse if the vacuum cleaner itself gets infested.

With all the challenges of bedbug control, Goodman says he sees people so overwhelmed that they do nothing but try to endure. Resistant as bedbugs are to many pesticides and superb as they are at hiding, he encourages people to try simple things that can at least knock down their numbers. “Bedbugs aren’t resistant to my foot,” he says.

Science News