Yellow Leaves on Pin Oak

Q:  The leaves of my mature pin oak tree are becoming more yellow as time passes.  I have tried the iron spikes etc. over the last couple of years with no result.  Could this be a fungus?  Should I have a tree expert come out and look at it?  Steve - Grimes  

A:  Your tree needs iron.  You can use iron capsules (Medicap) which are drilled into the tree.  Use according to directions on the box.  You could also apply iron using a Ross root feeder at the dripline with Green Again Pellets.