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Wild Things

The weird and wonderful in the natural world
Sarah Zielinski
Wild Things

Bedbugs survive cold, but not for too long

Bedbugs have been spreading in many regions around the world, leaving people struggling to figure out how to get rid of the pests.

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Insects rarely bug me. I don’t get spooked by spiders or terrified by termites. Mosquitoes annoy me, but only because I don’t like the inevitable itching that follows. Bedbugs, though, are my big exception. I’ve never encountered one, but I religiously check for them when I travel. And I’ve woken up from nightmares of them crawling across my bed and up my legs.

This is not an irrational fear. Recent years have seen a resurgence of the bugs, in part because of changes in pest management practices and a growth in international travel that has carried the bugs to new locations. And while the bugs aren’t disease carriers, an infestation can eat away at your mental health as well as your pocketbook.

Bedbugs are notoriously difficult to get rid of. Ultrasonic devices marketed to drive bedbugs away don’t have any effect. Bug bombs don’t work. Bedbugs are evolving resistance to a common insecticide that once killed them. (Even if the chemicals work, they can be dangerous for the humans exposed to them.) High heat can be effective, but that’s not always a practical solution.

Some studies have indicated that cold might kill bedbugs after as little as one hour of exposure. But new research published in the Journal of Economic Entomology finds that’s not the case. Cold can kill a bedbug, but only after days.

Joelle F. Olson of the University of Minnesota Twin Cities and colleagues froze bedbugs at various stages of life, fed and unfed, for varying lengths of time. The bad news was that the bugs didn’t die nearly as quickly as other studies had found, a mere hour or two at -16° or -17° Celsius. “In our study, bedbugs survived lower temperatures, with eggs surviving in short-term exposures … to temperatures as low as -25° C,” the researchers write. But the bugs are not freeze tolerant, the scientists found, and they can be killed — no matter their stage of life or feeding status. All it takes is 80 hours in temperatures of -16° C.

The finding confirms a standard practice for museum collections and food commodities: Potentially infested items are frozen to kill any hidden insect pests. And it provides a completely safe method of control for regular folk, at least for items they can fit into the freezer. The researchers advise:

Items suspected of infestation should be bagged before placement in the freezer to prevent bedbugs from exiting the items and perishing elsewhere inside the freezer. Bagging an item before placing it in a freezer will also protect it against changes in condensation or damage caused by moisture. Infested items should be placed in the freezer at -17.8° C (0° F) for a minimum of 3.5 [days], though time may be decreased to 48 [hours] if temperatures average below -20° C.

Not addressed, though, was whether even lower temperatures might kill the bugs faster. Perhaps a carbon dioxide fire extinguisher (-66° C) or liquid nitrogen (around -200° C) could kill in an instant. Items that wouldn’t fit in a fridge could then be disinfected within moments. I hope entomologists give such things a try, but in the meantime, maybe my brain can attempt such an attack in my next bedbug nightmare. Die, bugs, die.

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