Cold Winters: Their Positive Effect on Emerald Ash Borers

In recent times, thorough research programs have been carried out to establish a relationship between emerald ash borers’ infestation and climate change. The exact relationship between cold climate and emerald ash borer mortality varies from year to year.

Ash trees come in different sizes and may react differently to EAB activity. The EAB burrows under the ash tree’s bark, blocks its nutrient source, and slowly starves and kills the tree. The EAB larvae spread rapidly and kill many ash trees that come in its path.

The EAB larvae burrow deep into the bark of ash trees during the winter. The insects are able to survive the winter by secreting chemicals that keep them warm and prevent them from freezing. The only problem is; the chemical can only help to a certain point.

Some researchers in Minnesota, after a series of observations and tests, have concluded that when the temperature falls below -20, at least 50 percent of larva-stage emerald ash borers that fester on ash trees will die. If the temperature falls below -30, the death rate could increase to 90 percent.

Minnesota winters, especially in the northern region of the state, may cause heavy mortality of emerald ash borer larvae. However, even with the extremely cold air temperatures that were recorded in certain areas in Minnesota, some larvae survived through the harshest winters.

A representative at the Wisconsin Department of Natural Resources opined that it’s virtually impossible for the insect to go extinct in cold winters even if a polar vortex occurs. The cold will only help buy time for landowners to apply treatment and tree pruning measures to infected trees.