Powdery mildew on crabapple and apple. Photo provided by: University of Georgia Plant Pathology Archive, University of Georgia, Bugwood.org
Oak leaf blister. Photo found at: http://www.ppdl.purdue.edu/PPDL/images/TaphrinaOak1.jpg
Cedar quince rust on a juniper twig. Photo found at: http://www.uky.edu/Ag/kpn/kpn_09/pn_090414.html
Tag Archives: powdery mildew
Disease Hotline Issue 7
Frogeye leafspot on apple caused by Botryosphaeria obtusa. Photo by: Bob Mulrooney, Plant Pathologist Specialist, University of Delaware.
Powdery Mildew on flowering dogwood. Photo by: Bob Mulrooney, Plant Pathologist Specialist, University of Delaware.
Disease Hotline Issue 19
Horsechestnut leaf blotch. 
Coleosporium rust (Aster rust) on golden rod.
Powdery mildew on Leucothoe. All photos by: Bob Mulrooney, Extension Plant Pathologist, University of Delaware.
Disease Hotline Issue 18
Puffball. Photo provided by: Nancy Gregory, Plant diagnostician, University of Delaware.
Peony blotch on tree peony leaves.
Hollyhock rust. Image found at the following website: http://www.plantpath.iastate.edu/pdc/node/142
Powdery mildew. Photo provided by: Mike Schomaker, Colorado State Forest Service, Bugwood.org
Giant puffball. Photo provided by: Joseph LaForest, University of Georgia, Bugwood.org
Bacterial leaf scorch distant view. Photo provided by: Edward L. Barnard, Florida Department of Agriculture and Consumer Services, Bugwood.org
Bacterial leaf scorch. Photo provided by: Theodor D. Leininger, USDA Forest Service, Bugwood.org
Daylily leaf streak. Image found at http://hyg.aces.uiuc.edu/secure/subscribers/200611b.html.
Disease Hotline Issue 10
Dutch Elm disease. Photo by: William M. Brown Jr., Bugwood.org
Vascular staining by fungus. Photo by: Paul H. Peacher, USDA Forest Service, Bugwood.org.
Powdery mildew on roses. Photo by Bob Mulrooney, Plant Pathologist, University of Delaware.
Powdery Mildew on common lilac. Photo by: Whitney Cranshaw, Colorado State University, Bugwood.org.
Frog-eye leaf spot on red maple. Photo by Bob Mulrooney, Plant Pathologist, University of Delaware.