We just released our winter weather forecast, in which we call for a “teeth-chattering cold” winter. While some of the visitors to our website have let us know they are dreading it, others have commented that at least the cold will mean fewer bugs next summer. But is it true: do cold winters kill pests?
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.
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.
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.
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 pests remains to be seen. We’ll have to wait and see.