EAB and The Polar Vortex

Written by: Ron Gumz, Board Certified Master Arborist MN-0324B

Posted: 2019 | Emerald Ash Borer | Insect Control | Winter

Like many of you, we all stayed home on the days in January when the temperature dropped to 20 degrees below zero. All of our staff works through the winter, both in the office and up in your trees. When the temperatures fall below zero, we do not send crews out for safety reasons. At 20 below zero, we suggested EVERBODY stay home!

Days after this year’s Polar Vortex, we started to see various reports on the news about how the cold temperatures might affect emerald ash borer (EAB) populations. Reports showed up in both print and TV media that explained the cold has “saved” the Ash! Other reports stated that since the borers are insulated inside the tree, the cold did not harm them at all.

The U.S. Forest Service published an article after a recent cold spell to summarize research regarding extreme temperature impacts on EAB populations. We believe the USFS is the best source for using facts based on research and not using opinions on the subject. If you have Ash trees, we are encouraging you to read the full report here.

Here are some takeaways from the report:

• In USDA Plant Hardiness zone 5a (southeast Wisconsin), winter mortality of emerald ash borer is expected to be light
• Wind chill does not affect EAB
• Tree bark does offer protection to EAB larvae from low nightly temperatures
• EAB larvae naturally produces glycerol (which keeps larvae from freezing) to be able to tolerate cold weather
• The authors are not advising any short-term changes to the implementation plans to manage EAB

EAB has already caused significant mortality in our local untreated ash populations. If you have an ash tree in your landscape that you want to keep, treatment is essential to maintain its health. Unfortunately, the recent cold is not enough to provide an alternative to these treatments. There are other colder parts of the United States and Canada that are continuing to lose ash trees, even though they encounter temperatures much colder than this winter in Wisconsin.

The bottom line is that EAB is not going away due to the cold any time soon. Please call or email your Certified Arborist if you have questions about how our recent weather impacted emerald ash borer populations. We are here to be of service to you and your property!