Do Cold Winters Kill Bugs? Farmers’ Almanac

Do Cold Winters Kill Bugs?

Brrr! The Polar Coaster winter has definitely taken some dips and dives in temperatures. While some of the visitors to our website have let us know they are not happy about it, others have commented that at least the cold will mean fewer pests next summer. But is it true: do cold winters kill bugs?

Cold Winters, Fewer Bugs?

The answer is mixed. All insects have some ability to withstand cold weather. One of the most common strategies is to bury themselves underground, beneath leaf litter, or to burrow under tree bark for protection and hibernate for the season. These protective maneuvers work pretty well most winters, allowing insect populations to remain relatively stable.

A recent spate of warmer-than-average winters over the last few decades, however, has allowed the populations of some types of creepy crawlies to explode. When winter temperatures never reach a truly deep freeze, bugs make it through to spring unscathed and ready to multiply.

For instance, Lyme-disease-carrying deer ticks—which are not actually insects, but eight-legged arachnids, like spiders—are now seen in larger quantities and have spread farther to the north than they once roamed. When temperatures drop well below 0°F, though, many individual insects die. The colder the temperature becomes, the fewer survive. The problem is, the ground is warmer where they hunker down, allowing them to survive even some of the deepest freezes.

Most ticks can survive a deep freeze.

It’s All About Temperature

The actual temperature required to kill off pests varies across species. The emerald ash borer, for instance, can generally withstand temperatures as low as -20°F. Any colder than that and about half of their population dies off. At -30°F, even more of the invasive pests are wiped out.

Some individuals will inevitably survive, but the reduced numbers could be beneficial to other species. For instance, a substantial reduction in the number of emerald ash borers could slow the predicted extinction of American ash trees. Likewise, gardeners and homeowners aren’t likely to mourn if Japanese beetles or brown marmorated stinkbugs were less abundant next summer.

Fortunately, beneficial insects, such as honey bees, which are already threatened by a combination of commercial pesticides and widespread infection by a parasitic mite, are not likely to be impacted by a cold winter. Bees hibernate in their hives for the winter and huddle together for warmth, emerging in the spring to resume their annual flower feast.

Bees hibernate in their hives for the winter.

What About Fleas?

Fleas are a year-round nuisance, but they can die off outside when outside temperatures dip below freezing. In fact, once the temperatures fall to 37ºF, it’s cold enough to kill mature fleas as well as eggs, larvae, and pupae. But those temps need to be sustained for 10 days or longer. And that’s outside.

Fleas can be a nuisance year-round.

Inside the home, however, where it’s nice and toasty warm, fleas survive all winter long no matter what the temperature is outdoors. Often times, the pupae can go dormant in cool areas like basements or crevices in the home, then re-infest once the temperatures warm up again. You may need to treat pets year-round. Check out these natural remedies to kill fleas here.


According to Ohio State University, the temperature has a strong influence on termite activity—both on a daily and seasonal basis. In fact, some methods used by professionals in climates that never dip below freezing involve the application of liquid nitrogen. Termites exposed to freezing temperatures without shelter are usually killed within a short period of time.

The bottom line: the effect of cold winters’ ability to kill off bugs remains to be seen. We’ll have to wait and see.

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Behavior and Communication

Learn how different types of insects communicate with each other, other animals, and with the world around them in these articles.

Charles Henry Turner, Pioneer Animal Behaviorist

15 Fascinating Facts About Pill Bugs

10 Fascinating Facts About Dragonflies

Do Bugs Crawl in People’s Ears?

Can Fleas Live on Humans?

How Dragonflies Mate

How Do Insects Breathe?

5 Things You Didn’t Know About the Monarch Butterfly Migration

What Is Batesian Mimicry?

Courtship Rituals in Insect Mating

All About Insect Migration

Birds and Other Natural Predators to Control Mosquitoes

How Do Insects Find Their Host Plants?

What Aquatic Insects Tell Us About Water Quality

How Insects Attract a Mate

Spider Silk Is Nature’s Miracle Fiber

How Do Insects Have Sex?

Where Do Mosquitoes Spend the Winter?

What Are Social Insects?

How Do Insects Smell?

Why Do Termites Follow Ink Trails?

Millipedes, Class Diplopoda

Can Woolly Worms Really Predict the Winter Weather?

Why Are Insects Attracted to Lights?

Praying Mantis Mating and Cannibalism

How Do Crickets, Cicadas, and Grasshoppers Make Music?

Habits and Traits of Centipedes, Class Chilopoda

How Insects Taste Their Food

Insects That Defend Themselves by Playing Dead

Ever Wondered How Insects Hear the World Around Them?

Diapause in Insects

10 Ways Insects Defend Themselves

What Do Adult and Immature Dragonflies Eat?

Why Are Mosquitoes Attracted to You?

Why Do Bugs Die On Their Backs?

Why Insects Invade Your Home in Cold Weather

How to Control Invasions of Box Elder Bugs

Four Tips for Attracting Beneficial Insects to Your Garden

Sugaring for Moths

Darners, Family Aeshnidae

Can Insects Learn?

The Definition and Uses of Müllerian Mimicry

Where Do Insects Go During Winter?

Winter Survival Strategies for Insects

  • B.A., Political Science, Rutgers University

An insect doesn’t have the benefit of body fat, like bears and groundhogs, to survive freezing temperatures and keep internal fluids from turning to ice. Like all ectotherms, insects need a way to cope with fluctuating temperatures in their environment. But do insects hibernate?

In a very general sense, hibernation refers to the state in which animals pass the winter. 1 Hibernation suggests the animal is in a dormant state, with its metabolism slowed and reproduction paused. Insects don’t necessarily hibernate the way warm-blooded animals do. But because the availability of host plants and food sources are limited during the winter in cold regions, insects do suspend their usual activities and enter a dormant state.

So how do insects survive the cold winter months? Different insects use different strategies to avoid freezing to death when the temperature falls. Some insects employ a combination of strategies to survive the winter.


When it gets cold, leave!

Some insects head to warmer climes, or at least better conditions, when winter weather approaches. The most famous migrating insect is the monarch butterfly. Monarchs in the eastern U.S. and Canada fly up to 2,000 miles to spend their winter in Mexico. Many other butterflies and moths also migrate seasonally, including the gulf fritillary, the painted lady, the black cutworm, and fall armyworm. Common green darners, dragonflies that inhabit ponds and lakes as far north as Canada, migrate as well.

Communal Living

When it gets cold, huddle up!

There’s warmth in numbers for some insects. Honey bees cluster together as the temperatures drop, and use their collective body heat to keep themselves and the brood warm. Ants and termites head below the frost line, where their large numbers and stored food keep them comfortable until spring arrives. Several insects are known for their cool weather aggregations. Convergent lady beetles, for example, gather en masse on rocks or branches during spells of cold weather.

Indoor Living

When it gets cold, move inside!

Much to the displeasure of homeowners, some insects seek shelter in the warmth of human dwellings when winter approaches. Each fall, people’s houses are invaded by box elder bugs, Asian multicolored lady beetles, brown marmorated stink bugs, and others. While these insects rarely cause damage indoors – they’re just looking for a cozy place to wait out the winter – they may release foul-smelling substances when threatened by a homeowner trying to evict them.


When it gets cold, stay still!

Certain insects, particularly ones that live in higher altitudes or near the Earth’s poles, use a state of torpor to survive drops in temperature. Torpor is a temporary state of suspension or sleep, during which the insect is completely immobile. The New Zealand weta, for example, is a flightless cricket that lives in high altitudes. When temperatures drop in the evening, the cricket freezes solid. As daylight warms the weta, it comes out of the torpid state and resumes activity.

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When it gets cold, rest!

Unlike torpor, diapause is a long-term state of suspension. Diapause synchronizes the insect’s life cycle with seasonal changes in its environment, including winter conditions. Put simply, if it’s too cold to fly and there’s nothing to eat, you might as well take a break (or pause). Insect diapause may occur in any stage of development:

  • Eggs – Praying mantids survive the winter as eggs, which emerge in spring.
  • Larvae – Woolly bear caterpillars curl up in thick layers of leaf litter for winter. In spring, they spin their cocoons.
  • Pupa – Black swallowtails spend winter as chrysalids, emerging as butterflies when warm weather returns.
  • Adults – Mourning cloak butterflies hibernate as adults for the winter, tucking themselves behind loose bark or in tree cavities.


When it gets cold, lower your freezing point!

Many insects prepare for the cold by making their own antifreeze. During the fall, insects produce glycerol, which increases in the hemolymph. Glycerol gives the insect body “supercooling” ability, allowing body fluids to drop below freezing points without causing ice damage. Glycerol also lowers the freezing point, making insects more cold-tolerant, and protects tissues and cells from damage during icy conditions in the environment. In spring, glycerol levels drop again.

1 Definition from «Hibernation,» by Richard E. Lee, Jr., Miami University of Ohio. Encyclopedia of Insects, 2nd edition, edited by Vincent H. Resh and Ring T. Carde.

Plant Row Covers for Insect Protection

Westend61 / Getty Images

Row covers sometimes referred to as floating row covers, are lightweight spun-bonded synthetic fabrics that are laid over plants for protection against pests and temperatures. They are light enough to rest on the plants and allow light, water, and even fertilizer to get through.

Different Types

Most row covers sold to homeowners are made of either spun-bonded polyester or polypropylene. Row covers generally come in different weights, usually somewhere between 0.5 ounces per square yard and 2.0 ounces per square yard. The heavier the fabric, the more frost protection. Lighter fabrics don’t trap as much heat inside in summer months and allow more sun and water to permeate. However, they are all light enough to not need support and are allowed to ‘float’ on top of plants.

The lighter covers are used primarily as an insect barrier during the warmer growing months. Heavier fabrics are used for frost protection. The heaviest fabrics are used only in the evenings and are removed during the day to allow more light and heat access.

Frost Protection

Row covers will give your plants about two to four degrees of frost protection in the spring and a bit more in the fall because the soil is warmer in fall. That means that your plants will be protected from frost damage down to about 24 to 28 degrees F, depending on the fabric. You could also double the fabric, for additional protection when a frost is forecast. The row cover package should tell you what the frost protection for that product is.

Insect Protection

All weights of row cover work well for insect protection. But to keep pests out, you really need to seal or weight down all the edges and be especially careful that you don’t trap insects inside the cover. They’ll be fat, dumb and happy in there, munching on your plants in a warm, cozy environment. Check underneath periodically, to be sure nothing has hatched.

Bed Bugs can Survive Frost but Cold can Still Kill Them

Annapolis, MD; December 8, 2013 — Exposing bed bug-infested clothing or other small items to freezing temperatures may be a viable control option for people at risk of bed bug infestations. However, a new study has found that bed bugs may be less susceptible to freezing temperatures than previously reported.

In an article in the Journal of Economic Entomology called “Cold Tolerance of Bed Bugs and Practical Recommendations for Control,” the authors describe how exposing bed bugs to freezing temperatures affects them, and they provide practical recommendations for management of potentially infested items.

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Bed bugs, like many other insects, use a “freeze-intolerant” strategy against the cold, meaning they attempt to protect themselves from freeze injury by lowering the freezing point of their body fluids. For this study, the researchers evaluated the supercooling point (SCP) and the lower lethal temperature (LLT) for all life stages of bed bugs, as well as their potential to feed after exposure to sublethal temperatures.

The authors found that in order to achieve 100% mortality, a minimum exposure time of 80 hours at minus 16 degrees celsius is required for all life stages. Temperatures below minus 15 degrees celsius are sufficient to control all life stages of bed bugs after 3.5 days, while temperatures below minus 20 degrees celsius require only 48 hours. They also observed bed bug eggs surviving in short-term exposures to temperatures as low as minus 25 degrees celsius.

Homeowners can place bed bug-infested items in a freezer to destroy them. However, the authors recommend that the items be placed in plastic bags and that they remain in the freezer for 2-4 days, depending on the freezer’s temperature.

Where Do Mosquitoes Go in Winter?

Many people often lament over the final days of summer and dread the first frigid days of winter, but we’re guessing everyone may welcome winter this year with open arms, so they can bid adieu to mosquitoes and the threat of Zika virus.

Unfortunately, it’s a common misconception that mosquitoes simply die upon Jack Frost’s arrival. Read on to learn more about seasonal mosquito activity and how you can prevent a future mosquito problem from hatching come spring.

Mosquito Lifecycle

Believe it or not, mosquitoes do not simply die off during the colder months. Exactly how a mosquito survives the winter can differ by species. The mosquito responsible for transmitting Zika virus, Aedes aegypti, overwinters in the egg stage. As temperatures begin to fall below 50 degrees Fahrenheit, adult females deposit their final batch of eggs in water-holding items containing as little as a half an inch of water. The adults will eventually die, while the newly deposited eggs enter a state of diapause, a process that suspends their development during the coldest months.

When temperatures start to rise and rainfall picks back up again in spring, the eggs are re-submerged and hatch to start the next generation of pesky Aedes mosquitoes that will undoubtedly seek out humans as a food source. Even more alarming, though, is the fact that these offspring could be infected with Zika, as noted in a recent study published in the American Journal of Tropical Medicine and Hygiene.

Mosquito Bite Prevention

Regardless of where you live, it’s important to exercise caution when spending time outdoors this winter. The best way to do this is to carry over all of your mosquito-safe habits from the summer. Here’s what you can do:

  • Inspect your property now for water-holding items that could contain mosquito eggs deposited during the warmer months. These items may include flowerpots, birdbaths, tire swings, grill covers and other objects where water collects.
  • Homeowners should also unclog gutters, repair any leaky pipes or faucets on the outside of their home, drill holes in the bottom of tire swings and wheel barrels to allow water to drain, and ensure trash cans are tightly sealed and lids aren’t flipped upside down.
  • Apply an insect repellent containing at least 20% DEET, picaridin or oil of lemon-eucalyptus when spending time outdoors, especially in areas that don’t get much colder than 50 degrees Fahrenheit like Texas, Arizona, Hawaii, Florida and Southern California. Make sure to apply the repellent as directed on the label.

If you’re taking the proper prevention steps to guard against mosquitoes, these bothersome bugs won’t put a damper on your winter enjoyment. If you want to learn more about the potential risks of mosquito bites, click here.

Can Pests Transmit Coronavirus?

Now that winter has passed, it’s important to note that coronavirus is not spread by vector pests.

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