I read that Oak Wilt in Maryland appears to be isolated to a small area of Western Maryland, but we have lost two large oaks on our property in Mechanicsville, MD...and a third is dying. Our nearest neighbor has also lost one large oak. All are some version of the red oak family and died (or are dying) from the top down over a period of a year or two and I'm concerned that we are experiencing a new outbreak.
We know of no cases of oak wilt anywhere except in the extreme west of Maryland. We'd encourage you to send us photos of the trees--close up of the leaves and the entire tree.
There are many causes of tree decline, as you can imagine. Roots problems often lead to a top-down decline. Roots can be too wet, too dry, diseased, or out-competed. Here are some other lesser-known causes of tree decline: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG86%20Common%20Abio...
Another option is for you to contact a tree service company (or companies) and have them send out their arborist to access the tree. We only recommend arborists certified by the ISA (International Society of Arboriculture). You can find local companies with them by following the prompts at: www.treesaregood.org
Companies typically do not charge to look at and diagnose a tree, but check before they come.
Thank you for your quick reply. I will have to wait for the dying tree to "leaf up" before I can get a picture. It is lagging the oaks around it. I think it's a Bear Oak.