Growth in gardening: Cold will not kill the bugs

For insects that live in colonies, like bees, the main objective when cold weather strikes is protecting their queens. Although these beneficial insects are cold blooded, they spend their winters generating heat by fluttering their wings. The combined effort of all the bees is enough to keep them from freezing as they cluster together deep within their hive, with the queen always remaining in the warm center. PHOTO COURTESY OF JOE URBACH

With record-breaking cold temperatures in much of the United States recently, newspaper headlines have suggested that the freezing weather this winter could mean fewer insects next spring. For example:

– The New York Times: “Celebrating Deep Freeze, Insect Experts See a Chance to Kill Off Invasive Species”

– National Public Radio: “The Upside Of The Bitter Cold: It Kills Bugs That Kill Trees”

– Minnesota Public Radio News: “Extreme cold may wipe out high percentage emerald ash borer larvae”

However, to borrow a quote from Mark Twain, reports of insect deaths have been greatly exaggerated. While it’s true that insects will die if exposed to very cold temperatures for prolonged periods of time, many are able to survive, depending on the insect and the circumstances. Fortunately, the journalists who wrote the articles above balanced the optimistic headlines with more realistic views in the actual text after doing their research and talking to entomologists.

This is nothing new, of course. In fact, two years ago we faced a very similar situation when an extraordinarily mild winter gave rise to headlines about how the warmer temperatures would mean greater insect populations come spring. Mosquitoes for example would thrive, the thinking went, because of the lack of freezing temperatures. However, leaders of the Entomological Society of America said “Don’t Bug Out Over Warmer Weather” in a press release, explaining that lots of other factors affect insect populations besides temperatures.

The truth is that it is complicated! Which bring us to our current situation. While it’s true that extremely cold temperatures for prolonged periods of time can decrease insect populations, other factors are at play as well. While the cold may indeed kill off many insects, both harmful and beneficial, it doesn’t really make much long-term difference in insect populations.

In extremely cold regions like northern Minnesota and parts of Canada, where a significant portion of all types of insects die because of the cold, the effect does not finish the species completely. Thank heavens that our cold temperatures do not come close to those in Minnesota and Canada! If the bugs survive the cold there, you can bet they will still be going strong in San Marcos. Even with 50 percent mortality, insect populations will recover in a few years or so and continue on.

Have you ever wondered where bugs go in the winter? Or how they make it through to spring? Doesn’t anything kill these things?

These are the kinds of questions you may be wondering when you’re wiping ants off your kitchen countertop or spraying wasps that have accumulated in your window screen.

For many insects, the change in temperature is a matter of life and death. Some have adapted to survive temperature extremes as the seasons grow cold, while others have developed instinctual strategies to keep their species thriving when the weather takes its toll on an individual bug.

Whether they sneak inside your house or have their own way to keep warm, insects are survivors and understanding their cold tolerance levels can aid your efforts to control them.

There’s usually a noticeable drop in a number of insects invading your home when seasons change from summer to fall. It’s obvious the cold affects insects in some way, but how? And do different insects react to cold temperatures in different ways?

As you probably expected, many insects do indeed perish when cold weather strikes. This fate isn’t as harsh as it sounds, though. Most of these have already completed their true mission in life – to reproduce. These insects often spend their last days preparing the next generation for the upcoming spring. They do so by laying eggs in sheltered areas or providing their larvae with food and shelter to survive the winter, often at the expense of their own wellbeing.

One good example is the field cricket. Adults – and immature nymphs – can’t survive cold, winter temperatures. Their eggs, however, overwinter and will hatch in the spring, bringing forth a new generation of these pests.

Some Migrate. Some insects, Monarch Butterflies are a prime example, outrun the cold weather by migrating away from it. These insects usually engage in a one-way migration to warmer climates to the south where they reproduce, die and send a new generation northward to begin the cycle again.

Other insects, such as dragonflies, engage in a less direct migration. Their daily activities continuously move them toward warmer climates, and the insects never really experience prolonged cold weather. Instead, these insect populations cycle north and south each year.

Some Hibernate. Like many other types of animals, some insects will go into one of two types of hibernation to avoid cold temperatures. Called diapause, these hibernation-like states cause the insect to go dormant. This dormant period allows the insect to slow its metabolism and conserve energy and revive when temperatures rise again.

Some have a freeze tolerance. A few insects, particularly those with habitats in extreme latitudes, have developed the ability to survive ice formation within their tissues. They survive thanks to a natural antifreeze they can create. This antifreeze prevents the formation of damaging ice crystals and allows the insect to survive until they thaw. The famed woolly bear moth caterpillar is well known for its survival with the help of antifreeze.

Some just avoid the freeze. Probably the most popular cold-temperature defense mechanism of the insect world is freeze avoidance, which is a fancy term for “hunkering down for the winter.” These insects will retreat into rotting trees, bury themselves in the soil, hide inside a rotting log, and sneak into human-built structures to ride out the cold temperatures – a favorite tactic of ladybugs.

For insects that live in colonies, including bees, termites and ants, fighting off frigid temperature takes on an added scope. Most of these insects only care about one thing when cold weather strikes – protecting their queens.

So where do ants go in the winter? Most ant colonies will seal the entrances to their nests when cold weather hits and enter a dormant stage, living off their stored energy. Throughout the winter, they remain clustered together, underground, in large groups to maintain body heat and keep the queen warm. Without their queen, most ant colonies would only survive a few months.

Where do bees go in the winter? Like many of us, they just stay inside. Although these beneficial insects are cold blooded, they spend their winters generating heat by fluttering their wings. The combined effort of all the bees is enough to keep them from freezing as they cluster together deep within their hive. As they generate this heat, individual bees are constantly moving from the cool outer section of the cluster to the warm inner part. The queen, however, always remains at the center, increasing her chance of survival.

So, the bottom line is this; if you think a bitterly cold winter will knock back insect pests and reduce the damage they’ll do to your spring and summer gardens, you’ll be disappointed. But all is not gloom and doom. Our colder than-we-want winter temperatures this year, will help give plants that need cold weather to maximize flowering and fruiting enough chilling hours to help their buds fully develop. Bundle up, cover your plants and dream of the bountiful harvest to come!

--Joe Urbach is the publisher of GardeningAustin.com and the Phytonutrient Blog. He has lived in the Central Texas area for over 30 years. Urbach is a certified Texas Master Gardener from Hays County and is currently serving as the director of training. For more information on the Master Gardener program contact the Hays County AgiLife Extension Service at 512-393-2120.

San Marcos Daily Record

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