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Wednesday, July 4, 2012

Ashes in southeast Michigan today -- little consensus

A green ash in Ann Arbor that sprouted from base
There are many young ash trees growing in woodlots and along fence rows in our area. There is also a small number of mature white ash trees that survived the original onslaught of the emerald ash borer. This spring I saw an enormous specimen off Maple Rd within city limits that was greater than three-feet in diameter with little taper in the first 30' of trunk. It had never been treated. More rarely one will stumble across a green ash that managed to maintain its original single stem.

This tree in Detroit retained its original trunk.
Ask a professional if there remains a local population of borers still threatening the remaining trees, and you'll get a range of answers. Kay Sicheneder at the City of Ann Arbor insists they are still out there in dangerous numbers. Mike McMahon at GreenStreet Tree Care agrees. I have some doubts. Maybe the insect is out there in small numbers like the bronze birch borer, searching for weakened and vulnerable specimens. Maybe the population will rise and fall like the elm leaf beetle in Ann Arbor or the calico scale in Plymouth.

What I don't see in my rounds is any recent damage from the borer. The trees that were never trimmed of deadwood can be returned to respectability by the judicious use of a chain saw. There may be a problem that the sprouts are weekly attached to the roots or parent trunk and will fail under load as they get heavier, but this we'll have to discover as the trees develop.

This is not to suggest that one should discontinue treatments of important landscape specimens. It's just not known what the future will bring.

Note original stem in the center of this green ash
As to that large white ash in Grosse Pointe (bottom photo), a couple years ago I did not see evidence that insecticides had been injected into its trunk. I don't believe any amount of Merit or the Bayer soil chemical would have been adequate to chase out the borers, so the tree must have had some innate resistance.  This year I could tell that it had been treated with 'Tree-Age' via trunk injection.

A modest white ash in Grosse Pointe

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