Tree Branch Test
You might want to take a sample from your tree to the New Castle County Cooperative Extension office on Wyoming Road in Newark. There, you will fill out a form and give as much information as you can about the type of tree, the site, and so on. A good sample consists of something showing a margin between healthy and affected, or something beginning to die. A completely brown branch is difficult to tell much from. Someone from DE Cooperative Extension will be glad to take a look and get back to you.