Verticillium attacks most deciduous trees, especially, Maple, Elm, Beech, Ash, Apple, Cherry etc; Oak is considered resistant, however, it readily attacks stressed Oaks. Verticillium is probably the most common killer of deciduous trees here on Cape Cod. It is not a quick killer since trees are able to wall it off rather effectively. The problem comes when the disease breaks through the callus wall the tree builds. It's association with Bleeding Canker probably helps in this regard.