It's probably "Rust". Certain types of trees are more prone to it than others. The tree looks bad but it doesn't kill it. The infected leaves will eventually fall off. Rust usually affects my trees in the Fall. There is something you can spray on it but for the life of me I can't think of what it's called. If you ask at the garden section at Lowe's I'm sure they will know what it is.

The spray name is COPPER

Thanks guys! Karen