Question
We have an older white oak tree which gets good foliage each spring. However, around June 1 the leaves start to turn brown. The leaves do not drop until fall.  This has been occurring for approximately five years.  The first year it was just one branch, the next year a couple more branches, etc.  Not necessarily the same branches each year.  Probably by next year it will consume the entire tree.  We have tried insecticides (spray and systemic), iron applications to the ground and fertilizer.  Any assistance will be greatly appreciated.  (We are located in Michigan.)

Answer
Hi Sharon:
It would probably be best for someone to see your tree "in person" to give you a good assessment.  Sounds as if the condition is worsening each season.  This may indicate a potentail decay situation within the tree.  Check the trunk for such abnormalities such as loose bark or open cavities. Depending on the height of the tree, look for these thing up higher as well.  

Contact your local county Agricultural Extension office or local nursery about finding a certified arborist in your area to evaluate your tree.  These folks are much more qualified than the "fly by nighters" who want to sell you something.

Regards
Steve