This site provides information about Dutch elm disease and ELMguard - a new experimental preventative treatment being developed at the University of Toronto, Faculty of Forestry. Fire Blight Fire blight is a bacterial disease that affects apple trees, pear trees and rosebushes. About several tree diseases that can stunt or injure a tree over time. From University of Illinois Extension. The gypsy moth is a serious threat to trees including maples, oaks and elms.
Caterpillars feed on leaves, weakening the tree.
Oak Wilt Oak wilt is a devastating fungal disease that attacks red oaks, white oaks and live oaks of North America. Learn how you can identify and control this oak tree disease. Powdery Mildew Powdery mildew is a fungus that attacks the leaves of various plants including poplar and willow trees and roses. The Eastern tent caterpillar affects black cherry trees and other fruit and shade trees. The forest tent caterpillar infests hardwood trees such as sugar maple and oak.