Horsechestnut leaf blotch. Photo from: Bob Mulrooney, University of Delaware.
Photos for brown patch, roseslug sawflies (search roseslug sawfly), bagworms and fall webworms (Insect Hotline Issue 20, 2008 has best images) have already been posted. Please use search function to locate images.
Horsechestnut leaf blotch. Photo taken by: M. Petitjean, University of Massachusetts Extension & found at: http://www.umassgreeninfo.org/fact_sheets/diseases/guignardia_leaf_blotch.pdf
Cercospora leafspot on rose. Photo provided by: Paul Bachi, University of Kentucky Research & Education Center, Bugwood.org
Cedar apple rust. Photo provided by: USDA Forest Service – Region 8 Archive, USDA Forest Service, Bugwood.org
Cedar apple rust. Photo provided by: Daniel H. Brown, USDA Forest Service, Bugwood.org
Horse chestnut leaf blotch. Photo by: M. Petitjean, University of Massachusetts Extension & found at: http://www.umassgreeninfo.org/fact_sheets/diseases/guignardia_leaf_blotch.pdf
Oak infested with oak anthracnose. Photo provided by: Joseph O’Brien, USDA Forest Service, Bugwood.org
Oak anthracnose on oak leaf. Photo provided by: Joseph O’Brien, USDA Forest Service, Bugwood.org
Close-up of oak anthracnose. Photo provided by: Robert L. Anderson, USDA Forest Service, Bugwood.org
Bacterial leaf scorch. Photo provided by: Randy Cyr, Greentree, Bugwood.org
Glassy-winged sharpshooter vectors Xylella fastidiosa in grape plants, the same bacteria responsible for BLS. A possible vector. Photo provided by: Reyes Garcia III, USDA Agricultural Research Service, Bugwood.org
Grass sharpshooter is also known to vector X. fastidiosa in grape plants. Another potential vector for BLS. Photo provided by: Jack Clark, University of California – Davis, Bugwood.org
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.
Tree with symptoms of horsechestnut leaf blotch.
Horsechestnut leaf blotch. Photos of horsechestnut leaf blotch were found at the following website: http://www.ppdl.purdue.edu/PPDL/weeklypics/9-11-06.html.
This image of Phyllosticta leaf spot was taken from: http://ohioline.osu.edu/hyg-fact/3000/3044.html
This image of red thread was found at the following website: http://www.plantpath.wisc.edu/tddl/tddl/disimg/red/plant.jpg