Saint Paul, Minnesota...
Emerald Ash Borer vs. Fraxinus.
I took these pictures of Ash trees located in a St. Paul city park. The EAB was only discovered for the first time in Minnesota in spring of 2009. This is a technique called girdling, to make "trap trees" for detection and survey of the Emerald Ash Borer. By cutting the bark so severely, the tree becomes stressed, thus attracting the beetles.
These cut trees will die within 2 years now, but in the meantime during their decline, they'll become more and more attractive to the beetles and serve as a way of monotoring the infestation.
From the City of St. Paul website:
"The Emerald Ash Borer (EAB) is an exotic beetle that was first discovered in Michigan in July 2002, probably having arrived on solid wood packing material shipped from its native Asia. Without any natural predators or controls in North America, it has spread into nearby states, Canada, and now into Minnesota, having killed millions of ash trees along the way.
Unfortunately, wherever it has been discovered, there has been no stopping its devastation, though millions of dollars have been spent on a variety of prevention methods. The economic impact on states, municipalities, property owners, nursery operators, and forest industries has been overwhelming. Minnesota’s estimated 930 million ash trees could be decimated in Saint Paul, the metro area and the entire state".
Click the following link to go to my 2009 post about the Emerald Ash Borer in St. Paul: http://rockandrollgardener.blogspot.com/2009/07/mean-green-machine.html
This site explains it well: http://www.emeraldashborer.info/files/Using_Girdled_Trap_Trees_Effectively_For_EAB_Detection_Delimination_&_Survey.pdf