Tar Spot   (Rhytisma acerinum)

tar_spot.jpg (15736 bytes)Common Name(s): Tar Spot

Scientific Name(s): Rhytisma acerinum

Type: Fungus

Principle Host Trees & Shrubs:

Sycamore and other Maples (Acer species).

Description, Development & Diagnosis:

The fungus overwinters on fallen leaves. Fresh spores are produced in Spring which have a sticky coating. The spores attach themselves to the new leaves as they form. A raised, shiny black spot appears on infected leaves.


Common. Can cause premature leaf drop but the vigour of the tree is rarely affected. Rarer in cities due probably to fewer fallen leaves left under trees.


Generally unnecessary. If a problem on ornamental species dispose of fallen leaves in Autumn to reduce spore levels in Spring.

Further Information.

2001 Chris Skellern. AIE.    Home  | News | A-Z Index  | Resources  |  Contact AIE  |  Terms of Use