George said:

I have a fully grown, 25 year old ash tree. A few years ago some crunchy,
crab-apple type growths appeared on some of the branches. I must say I
didn't pay much attention, but last year a significant amount of the tree
was covered.

When removed, these growths crumble into small pieces. They are dark brown
in colour. The tree seems healthy otherwise.

I'm in Canada, Southern Ontario. I'd appreciate some advice on what is
happening., and what I can do about it.

How far are you from the Emerald ash borer area (extreme SW Ont.
in Canada)?

If your tree is in or near the area of infestation it's likely doomed. Keep an
eye on it to check for the possibility that you have an outlier infestation even
if you aren't in the effected zone. (I noticed these growths on some ash trees in
our neighborhood before the borers did them; they might have been a sign
that the trees were weakening.)

Info and link to a map of affected area in Ontario he
http://www.inspection.gc.ca/english/.../agrplae.shtml

Michigan sites on EAB:
http://www.msue.msu.edu/reg_se/roberts/ash/
http://www.michigan.gov/mda/0,1607,7...298---,00.html
--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)