Question
At least for now, the yellowing seems to be isolated to one fork of the tree.They are quickly yellowing & falling. We've had a cool,damp spring, with a sudden turn to 95-105 degree weather.I did spray my yard with a crabgrass killer. Could this be the problem?

Answer
Bob:
Some herbicides (weed killers) can cause tree damage, especially if they are applied on windy days that could cause drift to the tree leaves. If this occurred, best to just wait and see what happens now. In the meantime, have a look at that one fork that is affected. Look for bark damage etc, especially near the bottom of the fork where it attaches to the rest of the tree.
Regards
Steve