Since you have an ash tree, your tree may be impacted by the Emerald Ash Borer, a devastating insect that has killed well over 25 million trees since it has entered the United States. You can read lots more at: www.emeralsahsborer.info The insect starts in the canopy and works its way down through the branches and trunks. Green Ash are perhaps more sucesstable, but so far the insects attacks all species of ash trees. If this is a key tree in the landscape, there are both homeowner and commercial treatments. If not the borer, you may be seeing environmental impacts given it is the southern exposures.
