Tri-County News

Did the insects survive?


By Katie Winslow, U of M Extension

With the recent cold weather and heavy snow, there has been a lot of speculation about what insects will survive until spring. I think this is a fair question to ask when many of us may not want to be outdoors in the extreme cold, how the insects can possibly survive. The simple answer is: because they are really good at it, but it is a little more complex than that.

One major insect that I have been asked a lot about recently is the Emerald Ash Borer (EAB). The Minnesota Department of Agriculture and researchers from the United States Forest Service conducted a study in Grand Rapids, Minn., a few years ago. From this study, a model was created that predicts about 5 percent of EAB larvae should die at 0o F, 34 percent at -10o F, 79 percent at -20o F and an impressive 98 percent should die at -30o F. Now, if we stopped here, these numbers would look rather impressive. Although our ambient air temperature recently reached that level, with wind chills far lower, the EAB larvae did not necessarily experience those extreme lows. In order to get those kill rates the temperature beneath the bark of the tree must reach the subzero temperatures listed above. If the EAB larvae is low enough in the tree to have the extra insulation provided by the snow the temperature beneath the bark would be greater still. Some EAB larvae likely did not survive, but possibly more than one is still going strong beneath the bark.

In Minnesota and other cold states, insects have adapted over the years to survive the harsh winters. As humans, we should be grateful that they did. Although some insects can be harmful or annoying, many are beneficial to us and our food system. Some insects are freeze avoiding. This means that they can lower the temperature at which their body fluids freeze. They may also empty out their gut to avoid internal ice formation. Still others produce antifreeze proteins in their body fluids that bind to ice crystals during their formation to prevent the crystals from growing.

In addition to freeze prevention, insects find places to hide over winter. Just as the EAB is beneath bark and possible snow covered bark. Other insects hide under leaf debris, under the siding on your home, in garages and homes to survive the cold and emerge when they get the signal from Mother Nature come spring.

If you would like more information on garden insects and their contribution to our world, you can visit  www.extension.umn.edu, or call (320) 255-6169, ext. 1.

Portions of this article come from the Minnesota Department of Agriculture, University of Minnesota Extension and University of Missouri.

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