Will Our Sub-Zero Lows in Minnesota Reduce Insect Populations This Year?
It is not easy to find a "bright side" of temperatures approaching 30 degrees below zero. You would assume that one may be some insects in the topsoil would be killed with these really low temperatures that are in the forecast for this weekend? Many of them would likely be killed if the actual temperature at the top of the soil and a couple inches into the soil profile was at 30 degrees below zero! However, the soil temperature is actually about 55 degrees warmer than that!
The actual temperature at the 2 inch depth on February 10 from the weather station at the Southern Research and Outreach Center at Waseca was 28 degrees. At the 4 inch depth the temperature was 29 degrees. With 8 inches of snow cover the temperature at the soil surface is likely close to 28 degrees too. The frost depth is only 9 inches deep as of February 8 when the last reading was taken. This really shows just how good snow is at insulating the soil!
While the snow will protect insects overwintering on or in the topsoil these temperatures will likely kill some of the soybean aphids that are overwintering on buckthorn plants. It may unless they are on the lower part of the plant in the snow! I also read today that temperatures around 30 below zero may kill many emerald ash bores that are under the bark of ash trees. The emerald ash bore has been spreading in Minnesota so maybe this weather will save some of our ash trees.
I read that there are over 1 billion ash trees in Minnesota. After Dutch Elm Disease wiped out all our elm trees the ash trees were in their place, It sure would be a shame if we lost all our ash trees too! By the way, do you know the major way the Emerald Ash Bore is spread? People moving firewood from an ash tree that has not been debarked. The bores "hitch" a ride under the bark so, don't move firewood from an ash tree unless it has the bark taken off!