Verticillium wilt - This destructive disease attacks through the roots, causing the xylem to plug up. Prune out affected limbs. Avoid wounding roots, and water new trees. If replacing with another tree on the same site, select a resistant species. Tar spot - This is a fungal leaf disease occurring on Norway, red and silver maples.
Damage is ugly, but usually only cosmetic.
Picking up infested leaves reduces infection. Here is another fungal leaf disease. It shows up as a thin layer or patches of grayish white powdery material. Infected leaves may turn yellow and drop early. A cosmetic problem only.