Bed bug activity has stalled, and you’re no longer getting bitten. But, you’re concerned that bed bugs are dormant in the winter, hibernating, and waiting for the heat and humidity of spring and summer. Have you finally got rid of bed bugs or will they come back in a few months’ time?
Bed bugs breed, metabolize, and go through their life cycle more quickly when it’s warmer. But the effects of heat can be mitigated by indoor temperatures, so you might not notice this effect if your thermostat is turned up when it’s cold.
We’ll look at some studies into seasonal bed bug behavior during both the winter and summer (and, as it turns out, they’re fine with both). Then we’ll look at why bed bugs come back so often. Finally, we have suggestions on how to use extreme room temperatures to control or kill bed bugs.
Are Bed Bugs Seasonal?
The bed bug population has officially been skyrocketing since the turn of the century. Over this period, the U.S. has suffered from many summers—especially in 2010—where the newly resurgent species made headlines with how quickly they were infesting our cities again.
A paper in Environmental Health Insights titled The Decade of Bedbugs and Fear highlighted how the rapid increase was only matched by the panic that accompanied it.
Scientifically speaking, are bed bugs seasonal? It wouldn’t be unusual. There are all sorts of seasonal insects, from bees and wasps to flies and mosquitos. Each of these insects is most commonly seen during the summer, and are practically unseen during the winter. Adding bed bugs to the list would come as no surprise.
This is backed up by the experience of pest control companies. In a news piece published by Accuweather, a NYC pest controller stated that:
“Bed bugs peak in the heat. July and August are typically the biggest months for bed bugs. [They] tend to come out in the heat because they get dehydrated and more thirsty.”
The pest controller also claimed that they hibernated in winter. Another news item published by Business Wire claimed the same:
“Bed bugs continue to infest virtually anywhere humans congregate, making vigilance key to curbing bed bug infestations, especially as the summer travel season kicks into gear.”
But bed bugs are a different problem entirely to other kinds of insect. They’re an indoor pest. As such, they’re happy all year round, so long as you keep them at a comfortable indoor temperature.
Regarding their biology, though, they do breed quicker during warm periods and slow down their metabolism during cold periods.
What’s the Ideal Bed Bug Climate?
Where you can find humans, you can find bed bugs.
Bed bugs are, officially, an epidemic. They’re found in temperate climates across the world. As such, according to a paper in Clinical Dermatology, they can be found in all U.S. states.
Interestingly enough, bed bugs have historically been found only in developed countries. That’s because they can spread more easily in places affected by overcrowding.
However, there are many individual bed bug species. The one that affects us here in the U.S. is the common bed bug, Cimex lectularius.
Other species are more common in tropical reasons, such as Cimex hemipterus and Leptocimex boueti. These species are better adapted to warm weather but are less tolerant of the cold temperatures you find here in the U.S.
Unfortunately, tropical bed bugs have recently started to populate the south. A case of Cimex hemipterus was recently identified in Florida, the first report for over six decades. It was reported in the journal Florida Entomologist, which predicts that they will only spread from Florida to affect the whole of the south.
Both this species and the more common species Cimex lectularius, are gradually becoming immune to DDT and other pesticides. As such, we have a real problem on our hands.
Both populations are currently undergoing a resurgence, and show no sign of slowing down. Unfortunately, even common pesticides are losing their effects. But does this new species—or our ‘old friends’ C. lectularius—become dormant or hibernate in winter?
Are Bed Bugs Dormant in Winter?
So, do bed bugs go away in the winter? No—they don’t. They’re still active because of the temperature. They’re an indoor pest.
So long as they have access to a host, they won’t stop feeding just because it’s winter. However, their metabolism does, generally speaking, slow down during colder weather.
If you allow your house to become colder during winter, you may notice fewer bites, as they take more time between feedings. If you keep a constant temperature, you won’t see any difference.
Regarding developing a new infestation, though, you’re less likely to experience a problem. That’s partly because bed bugs find it harder to travel during winter. They’re not cold-resistant.
According to a piece in the Journal of Medical Entomology, bed bugs are less mobile in winter. They’re also less happy to travel because it’s cold outside. In many places across North America, it’s cold enough that they could die during a prolonged period of travel (e.g., to a hotel, or on a bus).
This is so much the case, the paper says, that they won’t even disperse in the face of insecticides, preferring to stay as close to their harborage as possible when it’s cold.
This is both positive and negative. On the one hand, it discourages them from feeding. But it also means that they’re less easily killed with these methods.
At What Temperature do Bed Bugs Hibernate?
So, bed bugs begin to become less active the colder it is. That much we know. But how does it affect their development? To understand how it works, first, we have to get a grasp on how bed bugs develop, grow and breed under normal conditions.
Bed bugs, like many other insects, go through many stages. The most well-known insect stages are larvae and adult forms, and we all understand that some insects go through dramatic changes over the course of their lifetime (e.g., moths and butterflies). However, many insects go through less obvious changes over the course of their lives, including bed bugs.
These stages are known as instars, and bed bugs must go through five before they reach full maturity. To develop, they shed their skin, which is why shed skins are a clear sign of an infestation.
To molt, a bed bug must feed on a host. Cool temperatures prolong the development process. This entire process is detailed in any number of scientific and pest control journals, including this one in the journal Insects.
- In warm temperatures, bed bugs complete development in just over a month. That means that each bed bug will feed on its host five times within a month, to become fully sexually mature. As you can imagine, in a large infestation, that means a lot of bites. Temperatures between 77 and 90 degrees are optimal for their development. That being said, without access to a host, bed bugs will not develop whatsoever.
- In cooler temperatures, bed bugs can take between one and two years to develop fully. Assuming the upper limit, that means that each bed bug will bite you around once every five months. Temperatures below 68 degrees are sufficient for these longer periods of development.
As you can see, then, bed bugs aren’t hibernating in the classical sense. But they are most definitely relatively dormant, and infestations in cool apartments and house, therefore,e take much longer to grow in number. However, it’s far from the truth that bed bugs die in winter or stop biting you. That’s why you still have to kill bed bugs, no matter the time of year.
How to Kill Bed Bugs in Winter
Can cold kill bed bugs? Yes, and no. These methods don’t always work, for many reasons. According to a paper in Medical and Veterinary Entomology, bed bugs are resistant to cold temperatures—to a certain degree.
Like plants, insects don’t produce their own body heat and must rely on the heat of external sources to warm themselves. You might think that they would die in the cold, but that’s far from a rule.
The paper above studied the topic in depth. They found that all bed bugs were killed by direct exposure to 3 degrees Fahrenheit.
For reference, that’s the average winter temperature in Alaska (although it does get much colder than that). That’s far colder than the majority of the U.S., although not unheard of in the north of the country. Even so, there are many reasons why you can’t always kill bed bugs with cold.
- This study used a constant, direct temperature. The coldest temperatures in the real world are made much worse by windchill. Bed bugs won’t experience windchill if they can still hide in their harborages. Not only that, but the temperature will vary anyway.
- Bed bugs use a process called rapid cold hardening to protect themselves from cold weather, but only if they’re allowed to acclimate. The longer they can acclimate at a more reasonable temperature—say, freezing—the better they can survive deeper colds. Cold hardening is an exceptional process where plants and insects use, for want of a better word, a form of antifreeze to protect themselves from cold weather. It would be impressive if it weren’t a way for bed bugs to survive.
- Because bed bugs’ metabolism slows down in cold weather, continual exposure to less-than-room-temperature makes them live longer. Their lack of access to blood meals means that they don’t continue in their life cycle, and they can live for up to a year waiting for renewed access to a host. In other words, they can easily last through the winter months, even outside.
Better than using the cold is to use insecticides and desiccants. As per a paper in the journal Insects, bed bugs avoid areas where these are spread because of evolutionary selection. Those that learned to avoid them were more likely to survive and breed. However, as we’ve learned, bed bugs are less mobile in winter. So, it’s the perfect time to use them.
Are Bed Bugs Worse in Summer?
What brings bed bugs out? There’s nothing quite like the warm and humid weather.
It’s a widely known fact about bed bugs that the warmer the temperature—up to a point, of course—the quicker they breed. A paper in the journal Insects titled Stress Tolerance of Bed Bugs reviewed their behavior in and ability to withstand increases and decreases in temperature. Their review stated that the incubation period of their eggs decreases as the temperature approaches 95 degrees. They can, therefore, breed faster during warm summer months.
Another reason why bed bugs are so comfortable during the summer months is their resistance to dehydration. The same paper in the journal Insects studied water loss in bed bugs and found that they are “extremely resistant” to dry periods, and are more resistant the older they are. Younger life stages that haven’t previously fed are vulnerable, but bed bugs are exceptionally good at holding onto fluid and nutrients, for up to a year after a meal.
That being said, bed bugs don’t wait for a year to have their next meal—not in the summer. They advance far more quickly through their life cycle in the summertime. This encourages them to feed far more often, up to once every five days. Once they’ve fed, they go back to their harborage to digest their meal; once they’re finished, they progress to the next stage of their life cycle. Five feeds after being born, and they’re fully grown.
However, the same paper does also reveal the fact that they aren’t immune to seriously high temperatures of 100 degrees plus. Naturally, high temperatures speed up their water loss substantially, which is the root of their increased desire to feed during this period.
So, while they like warmer weather, they’re not fond of heatwaves in the same way that cockroaches are. As you can see, it’s not a completely clear picture.
Why Are Bed Bugs Worse When It’s Hot?
It’s a simple case of mathematics.
Let’s say that you had a cold winter. You hardly noticed any bites, because the bed bugs slowed down their development. It would be tempting to think that your infestation was on the way out, but, rather, they were waiting for a warm summer. And all it takes is one month for a population of bed bugs to spiral out of control.
Let’s be generous and say that you start off with just one sexually mature female bed bug, ready to lay her eggs. Females can lay 50 eggs over the course of their lifetime, and lay around 7 per week; one a day. In a warm month, these eggs will each take one month to develop from egg to sexually mature adult. According to a review in the journal Entomology, Ornithology and Herpetology, this can result in an explosion from just one female to a colony of 31,700 in just half a year.
Like we said, simple math.
Aside from these factors, you also have to account for travel. Regional and international travel is a major factor in the spread of bed bug infestations. And people travel more in the summertime. This applies whether people typically travel to or from your city: they’re either bringing bed bugs with them or bringing them back.
How to Kill Bed Bugs in Summer
Summer is the worst time to develop new infestations, and for infestations to grow. It’s therefore important that you take many approaches to stop that from happening. Otherwise, your problem will, with 100% certainty, get out of hand. Let’s take a look at what you should do to get rid of bed bugs in summer.
- Buy a mattress protector. First things first, buy a mattress protector to separate yourself from any bed bugs in your mattress. A protector will make it physically impossible for any bed bugs to get in or out, and to bite you. This won’t kill them straight away—they’ll eventually starve after a year. However, it does reduce the likelihood that a new infestation will affect you.
- Always keep a bagged change of clothes for going out. Any time you leave the house, you may be taking an egg or bug with you. Conversely, any time you come back, you may be bringing one with you. To prevent this from happening, separate your ‘outdoor clothes’ from the rest of your clothes. Keep them in sealed plastic bags/bins so that a bug or egg you unintentionally brought home can’t start an infestation.
- Use bed frame traps to stop bed bugs reaching you. Bed frame traps stop bed bugs from being able to climb onto your bed frame. There is a number you can choose from double-sided tape, plastic cup traps, or even just cups of water. You place them underneath the feet of your bed so that no bed bugs can cross the room and climb up to bite you. They don’t necessarily kill your bed bugs, but they do reduce the size of your infestation if you empty them regularly.
- Kill as many as possible using desiccant dust. Last but not least, you should consider desiccant dust. According to another paper in the journal Insects, most are effective at killing bed bugs. They act by scraping away the outer layer of the bed bug’s shell. This outer layer is vital for their health since it helps them to retain moisture. Once it’s scratched away, they’re vulnerable to dehydration in summer temperatures.
- Regularly vacuum clean your mattress. Vacuum cleaning doesn’t kill bed bugs, but it does keep the population under control. By vacuum cleaning your mattress, you suck up half of the population you find. Make sure to use a vacuum cleaner with a bag, and to throw the bag away outside after use.
Because bed bugs develop, breed and lay eggs more quickly in summer, it’s vital that you do everything you can to reduce the population either through trapping or killing. Otherwise, the infestation can get out of hand, fast.
When to Kill Bed Bugs
So, the big question: when should you try and kill bed bugs? In summer, or in winter? Our answer is always going to be the same. Whenever you spot an infestation, you should take immediate steps to remedy it, whether that’s in summer or winter.
- In summer, if you leave an infestation to fester, it can get worse very quickly. Remember what we said just one bed bug could do over the course of six warm months? Plus, because they’re more mobile, they’re more likely to come into contact with any traps and dusts that you’re using to try and kill them.
- In winter, because they take longer to reproduce and develop, you have a real chance of being able to get rid of your infestation for good. It’s perfect timing to try and isolate bed bugs using mattress protectors. However, sprays and powders won’t work as well, because the bugs will isolate themselves in their harborages.
- That being said, there are many methods you can use to kill bed bugs in summer or winter. If you’d like to get started as soon as possible, you can skip forward to the final section below on temperature control techniques to kill bed bugs.
Isolation is what makes them so difficult to kill, either in summer or winter. Bed bugs are, remember, able to fit in any gap as wide as a credit card. That’s why you might think you’ve gotten rid of them all, only for one or two to come crawling back—even a year later.
Can Bed Bugs Come Back After a Year?
If you’ve read any of the above, you’ll already know the answer. Yes, bed bugs can come back after a year. It’s all down to how infestations start.
There are many ways that bed bugs can find their way into your home. There might even be a chance that your bed bugs simply survived the first round of treatment, and have been waiting to make their comeback ever since. Let’s take a look at how your bed bugs might have survived—or how you might be encountering a new infestation.
- Bed bugs are rapidly becoming immune to many treatments, including pesticides and desiccant powders. As such, you may have gotten rid of 99% of your infestation… But the 1% that were in good-enough hiding places managed to avoid it, and are now making a comeback.
- If you’re familiar with cockroaches, you’ll know that you can catch them from your neighbors. Bed bugs are no different. A post on com (a NYC real estate new site) highlighted the problem. They can travel across hallways, through cracks in your walls or floors, and right back to you. If you tackled your infestation, they could make their way back in a week or a year.
- One of the easiest ways to catch bed bugs is from a friend, colleague or family member. Bed bugs love to explore to find new hosts. They can find themselves tangled in clothing, rucksacks, handbags, grocery bags—anything they’re small enough to fit into. They can hitch a ride back home with you from work, or from when you visited a friend.
- Alternatively, you can catch them from a hotspot: a hotel or public transport. In big cities, bed bugs have spread like wildfire. They hitch a ride in clothing and bags and find their way to you in public, or in a hotel room while you’re traveling.
Unfortunately, because bed bugs are so common, they’re practically impossible to avoid in some cities. So, bear in mind that this might not be your bed bugs ‘coming back’. It might be an entirely new infestation. Not only that, but their exceptional hiding skills make it very tough to kill 100% of an infestation. Perhaps the best way, though, is to use heat and cooling techniques.
Here’s some information on whether vacating your home will kill off bed bugs.
Temperature Control Techniques to Kill Bed Bugs
There are many temperature control techniques that you can use to kill bed bugs. You can take advantage of both the heat and the cold to get rid of them, mostly without resorting to buying or hiring anything. Let’s take a look at how.
1) Turn Your Thermostat Down
First up, you should consider turning your thermostat down. As we pointed out above, bed bugs breed more slowly and develop more slowly in cooler temperatures. Consequently, if you keep your house or apartment relatively chilly, they’ll have a harder time growing and developing. And because the slower they develop, the less they feed, you won’t be bitten as much either.
This won’t kill them, but it will help you keep the infestation under control. And a manageable population—one that doesn’t breed or feed as much—is one that you’ll have a much easier time killing in the long run. You don’t even have the thermostat all the way down. It has a cumulative, progressive effect: the lower the temperature, the better. Anything below 77 is better than anything above, for example.
So, feel free to keep extra cool this summer.
2) Wash and Dry Clothing to Kill Bed Bugs
Next, you should wash and dry everything you can. Bed bugs hate heat; they also can’t breathe in water. Washing and drying them is the perfect way to make sure your clothes (and any other items you can launder) are entirely bed bug-free. This is the first step you should take towards actually killing an infestation in your room. You start a big clear-out, laundering all your clothes and bedding first, before moving on to manage furniture and mattresses.
Once you’ve washed and dried your clothes or other items, store them separately from everything else. This will prevent re-infestation. You can use large, thick plastic bags. Bed bugs can’t bite their way through plastic—or anything, for that matter—but there’s always a chance that a natural split or hole in the bag will let them escape. Either way, tie the bags air-tight so none can get in or get out.
3) Home Heat Treatment for Bed Bugs
Whole room heat treatments are a bed bug’s nightmare. It’s one of the critical methods that pest management pros use to kill bed bugs, especially those that are resistant to conventional pesticides. It’s simple: you keep the room at a steady 118 degrees over the course of a few hours, which is enough to kill both bed bugs and eggs.
Because heat is present for many hours, it has a chance to permeate everything in the room. This includes furniture, your box spring, your mattress and more. If you don’t leave the heater on for long enough, bed bugs in their hiding places won’t feel it. That’s why it’s important that you test the temperature throughout the room, rather than just the air.
Unfortunately, it’s not possible to perform a home heat treatment. You could, perhaps, get the air temperature of the room up to 118 degrees by using a portable heater and sealing all heat loss points in the room. However, without expert equipment, you would still be left with cold spots: underneath and inside furniture, for example, that wouldn’t heat up to the required temperature. Consult with a pest control technician if you need heat treatment for bed bugs.
4) Can You Freeze Bed Bugs?
Freezing bed bugs is possible if you use a freezer that’s cold enough. Unfortunately, hitting the necessary temperature isn’t easy.
According to a news piece at ScienceNews.org, bed bugs aren’t cold tolerant—at least, not tolerant of extreme cold. The piece described a study done at the University of Minnesota Twin Cities where scientists froze bed bugs at different stages of their life cycle, from eggs to fully grown adults. They found that bed bugs were tolerant of the cold until they froze solid. Many insects can survive being frozen, but not bed bugs.
The crucial point is the temperature they had to get to. Unfortunately, the bed bugs were happy to survive “short-term exposures” to temperatures as low as -13 degrees. However, they did find that bed bugs weren’t capable of surviving longer-term freezing. All stages of bed bugs, including eggs, die at 3 degrees over the course of 80 hours. According to the news piece, this is standard practice for museums and in food logistics, to kill pests. They made the following recommendation to kill bed bugs at home:
“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.”
They went on to say:
“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 (-4° F).”
Depending on your kitchen, these temperatures may or may not be possible for you to achieve. However, it’s a useful way to kill anything you can fit inside a ziplock bag, and inside your freezer. If you have access to one, a commercial freezer is cold enough to hit these temperatures.
So, to wrap things up: bed bugs bite more, breed more and spread more during the summer. But that doesn’t mean bed bugs are dormant during winter. Because you’re indoors, they can still bite and breed, just more slowly. Either way, whether it’s summer or winter, you have to be able to tackle your bed bug problem using either heat or another method.