Emerald Ash Borer (EAB) is turning up in  the Midwest, and leaving dead ash trees in its wake.  They have got ecologists and entymologists scrambling to understand what this means so that arborists and foresters can be prepared.

The Wisconsin Department of Natural Resources, UW- Extension and Dane County combined resources put together a presentation on EAB management strategies last week, and I got to sit in on it because I volunteered as a Master Gardener to help with registration and refreshments.

What I learned was pretty grim.

This deceptively gorgeous green bug is presumed to have arrived in the U.S. from China about 15-20 years ago. They probably made the journey in solid wood packing material

Adults munch on the leaves of ash trees.  That’s not the problem.  The female lays eggs on ash trees that hatch into larvae.  Those larvae chew through the bark and begin to feed.  The wood goes in their front end.  What comes out their back and blocks up the tree’s plumbing.  Pretty soon leaves in the top of the tree are starting to die.  Ultimately they all will. By the time the canopy of a tree is half dead, the party is over.  Turn out the lights, and fell that tree.

Thewhite areas now have EAB infestations, and the red dots represnet actual sitings.

The first EAB sighting was in Detroit in 2002.

In less than 10 years they have killed tens of millions of ash trees, and before they are done, it is likely they will kill every one.

How are these little destroyers getting so far so fast?

Well, the adults can fly.  Though beetles are normally poor flyers, both the Japanese Beetle and the Emerald Ash Borer are good flyers.  Nonetheless, they can only fly about ½ a mile in a year.

They can move much faster when people carry firewood in their cars and trucks.  Many new infestations of EAB in the Great Lakes area are caused by people moving infested firewood.  We need to purchase our firewood near where we plan to use it.  Use iall, or leave it behind.  Never carry your firewood any distance.

The critters can also hitch a ride in infected nursery stock and ash wood products.  Ash is an extremely hard wood often used for tool handles.

If you don't know what ash trees look like, this will help.

Scientists have been working fast, racing to stay ahead of the EAB and form some kind of a strategy to combat it.  They are developing pesticides that can protect individual trees for an unknown amount of time.

At the seminar, about 65 arborists and city foresters were listening carefully.

Tres can be protected by treatment.  It isn’t cheap.  A professional arborist will need to inject pesticide into the tree.  But not every tree can or should be protected.  If the tree is already infected, you are putting money into a sinking ship.  If the tree has structural problems — you need to let it go.

What the arborists and foresters at the session I attended were told is that there is ultimately no way to save their  ash trees, but that they should treat them with the pesticides anyway.


Because treatment will slow the die off.  If all the ash trees all die at once, it will be a huge economic burden on a community.  Treatment will cost less than just letting the trees all die at once and then having to remove and replace them.

Purdue University has developed an Emerald Ash Borer cost Calculatorto help forest managers make good decisions.

If you have an ash in your yard that you love, you may be able to keep it for quite a while.  You need to be aware of how close EAB is getting to your area.  There is no need to apply preventative treatment before they are getting close.


  • Is it a true ash? (EAB only kills true ash – not mountain ash.)
  • Does it have 3 or more of the symptoms below?
  1. Thining crown
  2. Bark chipped off by woodpeckers
  3. New growth on trunk
  4. S-shaped tunnels beneath bark
  5. D-shaped holes on the bark about the size of a small lentil
  6. Splits in the bark

To learn what you need to know about Emerald Ash Borer, Purdue also offers online self-study programs.  They have study guides tailors for arborists, home owners and privately-owned campgrounds.  Knowledge is power.  Check it out here.

Categories: Eco activism

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