Spring Insect Outlook Impacted by Cold Winter?


With the severely cold temperatures that have marked this winter, many people are wondering if the cold will at least kill off some of the more pesky insects that begin to plague us in the spring and summer. The jury is still out on the answer.

Local growers we talked to said they were looking forward to the potential for smaller populations of some insects this year:

"The insect pressure for white flies and tomato horn worms have been pretty high the last few years, and I'm looking forward to maybe not quite as high a pressure on that, and that we can have a good growing season," said Gwen Coobs, owner of Allens Grove Greenhouse.

But when it comes to the question of whether the extreme whether actually will make a real difference in the insect populations this spring, the answer is "maybe".

"We'll just have to wait and see," said Scott County Extension Horticulturist Duane Gissel.

"I mean it will probably have an impact, some impact on it, but probably not as much as we are hoping for," he said.

Gissel says insect survival rates depend on everything from the species of bug to where its spends the winter and what the rest of the season brings.

For example, insects that over winter in the soil usually live through even deep frosts, because they just burrow deeper into the ground.

"So it doesn't always impact them, but it certainly could," Gissel explained.

Ticks, which spend the winter in leaf debris in high grass, can also usually make it through the extremes, too.

Same goes for water-dwellers. A lot of mosquito eggs can survive the entire winter in sub zero temps, only hatching when the environment is suitable.

"There are some adults that are out there that have found some spots to try to overwinter," Gissel said.

Of course, some insects, like the Marmorated Stinkbug and Asian Lady Beetle, try to find warmer hideouts inside our homes or under the siding on our houses to escape the winter weather.

"It may impact the populations on those if it gets cold enough," Gissel said, "as long as they haven't gotten far enough into the wall cavity of our homes to stay warm."

One pest population that likely will be impacted is bagworms, which have moved north into our area over recent mild winters. The moths lay their eggs in cocoons in junipers and other evergreens, and their name-sack 'bags' provide very little protection from the extreme cold.

"So if you've been having trouble with bagworms in your landscape, it probably will impact them. You'll see lower numbers," Gissel said.

It's hard to say how cold would ever be cold enough to actually kill off the heartiest bugs, though.

Ongoing research, especially on the Emerald Ash Borer, has been delivering mixed results.

"Right now, we really don't know for sure, but we're hoping," Gissel said.

"It's wait and see on most all of them," he added.

Keep in mind, even if the insect population is down by the end of this cold winter season, it won't take much time at all for the bugs to repopulate and bounce back to their normal numbers.

And, it's also important to keep in mind that there are some beneficial insects we *want* to survive the winter.

Bees and other pollinators are big for crop production -- and even a lot of the caterpillars are an essential part of young birds' diets.

We'll see how they all fared whenever we finally warm up.

Gissel says the cold weather will have an impact on some plants, too.

We could certainly lose some Japanese Maples and other less-hearty species, and it's already pretty certain we won't have any peach crop in Iowa at all. Those buds are killed off by any temperatures under 18 degrees in the winter.

This winter, 18 degrees feels balmy.

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