Cornell University. Cooperative Extension of Suffolk County. Horticulture Diagnostic Laboratory.
See also: Tree and Shrub Disease for more fact sheets.
Michigan State University. Center for Integrated Plant Systems.
See also: Plant Diseases for more fact sheets.
University of New Hampshire. Cooperative Extension.
University of Illinois Extension.
University of Kentucky. Cooperative Extension Service.
See also: Woody Ornamentals for more fact sheets.
University of Massachusetts Extension. Landscape, Nursery, and Urban Forestry Program.
Oregon State University. Extension Service.