I'm always on the lookout for any new thoughts on diseases that affect maples and how to treat them, when I saw this article that showed that it is not important to pick up and burn to prevent infection for the following season. Are your maple leaves dotted with black spots? They’re called ‘tar spots’ and here’s what they mean Don't know whether I would risk it, as it goes against every bit of advice I have obtained over the decades. But maybe worth a try!!!
I'd agree; it doesn't do any significant harm to the trees. One interesting point: in Britain, I see it almost exclusively on Acer pseudoplatanus; I've not seen it on Acer platanoides. Websites from North America (as in the above one from Toronto) show it almost exclusively on Acer platanoides. Presumably different species / subspecies of Rhytisma are involved. Which maples do others see it on, where?
Good afternoon Michael, the same down here, only occasionally on A. psudoplatinus but nothing else. Interesting that Wiki listed 3 Acers most affected from Rhytisma but not from different species or sub species. Rhytisma acerinum - Wikipedia But a very good observation by you.
I don't rake leaves with tar spot, because it would be impossible. The Augean labors of Hercules would pale in comparison. Sycamore is very common, many are affected, leaves blow. The particular subjects that get tar spot and in what severity varies from year to year. I agree that the species of fungus probably plays a role, but AFAIK no one has really studied the question. In the NE of America it is often seen on A. saccharum. Here we have never seen it on that species, but the related grandidentatum suffers yearly. We sometimes see a little on A. platanoides, but very minor compared to pseudoplatanus: most trees from Sec. Platanoidea seem unaffected. A. spicatum can be quite badly hit. It really does seem to vary greatly by region.
