Pests and Winter Temperatures
Baby It's Cold Outside!
Wow! This is the actual temperature we are experiencing here in the Upper Midwest. Not necessarily unusual, and certainly not pleasant to deal with. We have our share of cars that won't start, pipes that freeze, not to mention frostbit noses and toes!
But are there some benefits? YES!
Some pests thrive even in cold temperatures. They are insulated under tree bark or burrowed deep in the soil. But temperatures of -20 to -30 is pretty extreme and has reached these lows a few times already this year with more to come. So what is this doing to our pests?
We may very likely see some reduction in pest problems next season. So far snow cover is minimal. Snow insulates the soil, keeping it much warmer than we might expect. The extreme temps and unusually small snow depth has allowed soil temperatures 6" down to reach -15 degrees already. The soil is frozen anywhere from 12 to 20 inches deep. Even Iowa, Nebraska and parts of Illinois have soil temperatures of about 5 degrees and getting colder every day.
As the temperatures plunge in fall, insects larvae and grubs typically burrow deeper. Not likely they went deep enough this year. With extreme cold, little snow depth, deep frost levels and very likely prolonged cold soil we can be very hopeful the certain pest problems will be minimized if not dramatically reduced in the coming growing season. Thank goodness bees seem to survive just fine!
These are the pests that will likely be affected by our extreme cold:
Japanese Rose Beetles - 15 degrees kills the grubs buried in the soil
Emerald Ash Borer - larvae in the trees will begin to die off when the inner temperature reaches -15. At -30 nearly all will die. Like most pests, the Emerald Ash Borer has ways of preserving themselves but it is likely we will lose at least 80% this year.
Wood Ticks - Several days sustained at -10 degrees will kill most ticks.
Annual White Lawn Grub - Will not likely be below the frost line this winter and most will be killed.
Gypsy Moth - Will freeze to death at -15 to -20 degrees.
Box Elder Bugs and Asian Lady Beetles - Those that are outside will likely die, however they primarily overwinter in the warmth of tiny nooks and crannies under your siding and walls.
Unfortunately, those that survive will begin to re-populate relatively quickly. Enjoy it while you can.
Late 2018 Update:
The scientific consensus last year during or deep freeze is summed up here: “Sorry gardeners, this brief arctic chill won’t halt the Japanese beetle invasion, entomologists say. “ (Omaha World Herald).
BUT, as a matter of personal observation, I don’t think it applies to the Minnesota experience. First, we did not have what most would consider a “brief” arctic chill. Up here it was extended, freezing the soil deeper than I ever remember. The very deep freeze caused the demise of some plants, but I believe also the death of insects and larvae that certainly did not burrow deep enough to escape the deep freeze.
I can’t speak for other areas of the country but I observed a dramatically reduced population of Japanese Beetles in my own gardens as well as the nearby large public rose gardens (which in many years is horribly devastated by the Japanese Beetle). So for at least one season I have enjoyed undamaged blooms and hope the population recovers slowly.