Rhytismataceae

Rhytisma

Acer circinatum

Alaska

California

Oregon

Washington

British Columbia

Acer macrophyllum

Acer pensylvanicum

Connecticut

Georgia

Kentucky

Maine

Maryland

Massachusetts

Michigan

Minnesota

New Hampshire

New Jersey

New York

North Carolina

Ohio

Pennsylvania

Rhode Island

South Carolina

Tennessee

Vermont

Virginia

West Virginia

Wisconsin

Acer spicatum

Alabama

Iowa

Manitoba

New Brunswick

Newfoundland and Labrador

Nova Scotia

Ontario

Prince Edward Island

Quebec

Saskatchewan

Saint Pierre and Miquelon

Rhytisma punctatum

Rhytisma punctatum

Hosts: Acer macrophyllum

first symptoms of tar spot appeared as round, light-green lesions on leaves [in mid-July]. Tar-like stromata within the light-green lesions were well-developed [in October].

Spermogonial stages apparently are not produced by R. punctatum on A. macrophyllum, but have been reported on A. pseudoplatanus L. according to Tubeuf and Smith (15) and Massee (6). This possibly indicates that the fungi attacking these hosts are different species.

The Life History and Cytology of Rhytisma Punctatum on Bigleaf Maples

Rhytisma punctatum was originally described on maples in Eurasia (eg Acer pseudoplatanus). However, this species seems likely to be distinct from the "R punctatum" found on native North American maples. Within North America, this name is applied to both a set of galls found western A macrophyllum/glabrum/circinatum and another on eastern A spicatum/pennsylvanicum; evidence that these two fungi are the same species as each other or the European species is lacking. 

Even given this uncertainty, the host range of this species is not precisely delimited. [Hsiang and Tian list](https://atrium.lib.uoguelph.ca/xmlui/bitstream/handle/10214/2370/08_hsiang_tian.pdf?sequence=1) R punctatum only on Acer macrophyllum and circinatum, and speculate that the Rhytisma on Acer spicatum is americanum or acerinum. [Hudler and Jensen-Tracy](http://www.cybertruffle.org.uk/cyberliber/59575/0068/0409.htm) assert that R punctatum is found on Acer saccharum and pennsylvanicum in North America. Bladmineerders doesn't list Rhytisma punctatum occurring in Europe at all. [Corlett and Catling](https://www.biodiversitylibrary.org/page/59111575#page/10/mode/1up) list R punctatum on even more species, including A macrophyllum, pensylvanicum, negundo, rubrum, saccharum, and spicatum. It isn't clear how reliable these reports are.

There is no genetic or morphological evidence that R punctatum occurs on Acer platanoides; this misidentification is commonly made because R acerinum is spotted before coalescing later in the growing season. 

Gallformers ID Notes