Tar Spot Rhytisma acerinum

Scientific Name: Rhytisma acerinum (Rhytismataceae). The specific name indicates the connection with Maples Acer spp.

English Name: Tar Spot. It is an Ascomycete fungus (a type of sac fungi).

French Name: La Tache goudronneuse (='tar spot'). Also les Croƻtes noire de l'Erable (='maple black scabs').

5 Key Characters:
  • affects maples and sycamores.
  • appears in late summer and autumn.
  • first sign is yellow spots on the leaves, which become black.
  • black spots can be up to 4 cm across.
  • does not kill the tree and there is no resistance to it.


Habitat: Maple and sycamore trees Acer spp.

Fruiting Period: August-September-October-November.

Status: Very common. It is rare to see an unaffected Sycamore Acer pseudoplatanus.

Photographed by Loire Valley Nature:


  1. It is about the ONLY lifeform that Sycamore supports...
    a tar spot fungus also affects roses!
    It doesn't seem to affect our Norway Maples or the Field Maples here.

  2. Tim: do you mean black spot? If so, that's an unrelated fungus.

  3. Probably is unrelated, [I did use 'a'], but I have seen it refered to in rose books as tar spot...
    for which the only cure is application of lots of nasty sulphur loaded chemicals early in season...
    interestingly the roses up around Teeside don't suffer, can't think why?
    However Cocksfoot grass on Teeside is a rather unhealthy dark marroon colour...
    still with all those ICI waste fumes around????