Tar Spots and Bonsai

Hey, how do you get rid of tar spots on your trees? EVERY maple in my neighborhood has it and I'm struggling to keep it off of mine. What should I do to keep it away?

"Tar" spots?

What tar? Where does it come from?

Do you have pictures?

From Purdue University:
"Answer: Tar spot on maple is not actually "tar" on maple, but rather a fungal disease. Tar spots on maples are caused by fungi in the genus Rhytisma. The most common species are Rhytisma acerinum and R. punctatum.
Symptoms first appear in late spring or early summer as infected leaves develop light green or yellow-green spots. During mid to late summer, black tar-like raised structures are formed on the upper surface of leaves within the yellow spots. R. acerinum causes spots that are 0.5 to 2 cm in diameter; R. punctatum causes spots that are smaller (about 1mm in diameter). Spots caused by R. punctatum are sometimes called speckled tar spots.
Tar spot diseases seldom are detrimental to the overall health of infected trees. Tar spots may cause premature defoliation, but are not known to kill trees. Tar spot diseases are best managed by raking and destroying fallen leaves because the fungi overwinter on leaves."
For bonsai, it might be prudent to spray with a fungicide.
Iris

Ahhhh. Thanks, Iris.

The funniest plant health advice I ever saw in a newspaper was for homeowners to put maples leaves with tarspot in compost heaps, but only with the leaves placed upside down. I think it's fine to compost the leaves any which way, as long as it's away from the trees, since the fungus overwinters on fallen leaves.

Essentially, tarspot is not a big deal. Rake up diseased leaves and keep them away from your bonsai. The end.