Bur Oak Blight

"A serious leaf blight disease on bur oak has been recognized in several Midwestern States since the 1990s with Iowa reporting its first occurrence of this disease 6 or 7 years ago. A common leaf spot fungus, Tubakia dryina, was initially thought to be the cause of the blight on bur oak, but closer examination revealed a different story. Researchers in Iowa confirmed that this disease is caused by a new, and yet unnamed, species of Tubakia. The disease was named bur oak blight, or BOB for short. 

There are now five known species of Tubakia that can infect bur oak in Iowa, but only one species causes dramatic leaf symptoms and tree mortality characteristic of BOB." - Pest Alert: Bur Oak Blight (attached guide below)