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Emerald Ash Borer On Minnesota's Doorstep

Jeffrey Hahn, Asst. Extension Entomologist

Earlier this month, on April 7, Wisconsin reported a confirmed infestation of emerald ash borers (EAB) in the town of Victory.  This town is in Vernon county, about 20 miles south of La Crosse and on the banks of the Mississippi River about one mile from the Minnesota-Iowa border.  This the first time that EAB has been found in western Wisconsin.

The Minnesota Dept. of Agriculture has stepped up their surveillance efforts in Houston county which is right across the river from this infestation in Wisconsin.  So far, their surveys have not revealed any EAB.  Remember, that at this time, EAB has not been found in Minnesota (although the odds of finding it in Minnesota soon have gone dramatically up).  Because of the imminent danger of EAB, a quarantine has been put in place for Houston county, restricting the movement of ash trees, ash logs and branches, uncomposted wood chips, and any hardwood firewood.

Photo 1: Minnesota quarantine area. Note, the yellow do is a confirmed EAB infestation. MN Dept. of Ag.

Minnesotans should be greatly concerned about EAB.  Minnesota has one of the largest concentrations of ash in the U.S. with about 900 million found in our forests and urban landscapes. This insect is such a severe pest as it attacks all species of ash, regardless of size or state of health, killing them after three to four years of tunneling under the bark.

Photo 2: Emerald ash borer. Jeff Hahn

What can you do to help?  First and foremost don’t move firewood from outside of Minnesota into the state.  In fact don’t even move firewood within Minnesota.  If you are going camping or any activity that involves firewood, buy it locally from an approved vendor, don’t bring firewood from home.  And when you return home, don’t bring extra firewood back with you.

This is so important because firewood is the primary method EAB has for being moved long distances.  By itself it only flies about ½ mile a year.  But with peoples’ help it can travel hundreds of miles at a time.

People can also help by being aware of what emerald ash borer looks like and the symptoms of an EAB infested ash tree.  An emerald ash borer is a slender, ½ inch long, iridescent green beetle.  It is active anytime from late May into August. There are other insects ( in Minnesota that are also green so look closely.

Be alert to trees that are suddenly showing signs of thinning foliage and dead limbs.  An emerald ash borer infested tree will show signs of D-shaped exit holes (although they may not always be easy to see).  If you were able to look under the bark, you would find a series of S-shaped tunnels backed with frass (sawdust and insect droppings).  Although there are other problems that can cause to ash to dieback (, it should be a red flag that should cause one to look more closely.  Use the ‘Do I Have Emerald Ash Borer’ diagnostic web page ( on the Minnesota Dept. of Agriculture web site for help in deciding whether you have EAB.

For more information on emerald ash borer see,