The American Elm was once a  fast growing, shade providing, poor soil tolerating tree along city streets. In the 1900’s, logs were brought from Europe introducing the elm bark beetle and a fungus that causes Dutch elm disease. Dutch elm disease spreads rapidly. Plant breeding programs and research by the U.S. National Arboretum and Chicago’s Morton Arboretum have produced a few cultivars, but the research to disease resistance continues. The American Elm is now being affected by elm yellows. Elm yellows is caused by small phytoplasma that affects the phloem. It is carried by leaf hoppers. Ash trees are threatened by emerald ash borer and ash yellows. Red oaks are now threatened by oak wilt and bacterial leaf scorch. The best way to avoid complete devastation in your yard is to plant a variety of tree species in your landscape.  Information provided from Cooperative Extension Ornamentals Hotline.