We have a tatarian maple tree, all the leaves have spots on them. We went to the Toronto master gardeners and they think it’s a fungus. Enclosed is a pictures for you to see. We appreciate your help to recognize the problem. Please email me at your earliest convenience.
Thank you for contacting the Toronto Master gardeners with your inquiry.
From you photo it is difficult to tell if your maple is suffering from tar spot or maple anthracnose. Tar spot is caused by the fungus Rhytisma acerinum or R. punctatum. Leaf blight ( maple anthracnose) is caused by several fungi ( Aureobasidium apocryptum, Discula campestris (Gloeosporium), Discula umbrinella and Colletotrichum spp.)
Proper control measure of these funagal diseases are similar and can be found in two of our earlier posts:
You may also be interested in this article from Penn State University which list maple diseases and their symptoms.
Also you might find the article titled Blasted Blight on out Beautiful Maples of use.