oak tree stress/death
I have a tree farm in Goodhue County consisting of oaks, walnuts, and pine. There are about 2,000 red and 2000 white oak and burr oak. I have noted stress in some red oaks that I transplated to a lawn about 20 years ago. The leaves are curled each year when the weather is warm and the number of leaves are reduced. Photo 195 shows the red oak. The burr oak leaves appeared to be eaten by something when it became warm. The trees have mostly leafed out again. photo 196 shows stressed burr oak leaves. Photo 199 shows a dead burr oak in an otherwise healthy looking plantation.
That is a lot of oak trees. I'm sure you are aware of oak wilt. I can't say for sure if that is what you might have but it seems like a possibility. I will provide a couple of links with info for you to read through and compare to your problems. Red oaks are more susceptible but white oak can also be infected. The disease is transferred by beetles and through the roots once the tree is infected. It is hard to say what might have chewed on the leaves. You could have a certified arborist come and take a look at your trees and tell you what it is. Make sure that they are certified. You could also send a sample to the disease clinic at the U. http://www.extension.umn.edu/environment/trees-woodlands/oak-wilt-or-anthracnose/ , http://www.extension.umn.edu/environment/trees-woodlands/oak-wilt-in-minnesota/ . http://www.treesaregood.com/findanarborist/arboristsearch.aspx . http://pdc.umn.edu/.