Tar spot is a fungal leaf spot disease of sycamore and some other Acer species.
Tar spot is caused by the fungus Rhytisma acerinum. This fungus overwinters on fallen leaves. In the spring, sticky spores infect the healthy leaves of some species of maple trees through the leaves’ pores (stomata). Yellow spots appear, later discoloring to black. The tree is not harmed by this fungus; it just doesn’t look pretty.
Where to find
- Sycamore maple (Acer pseudoplatanus )
- Norway maple (Acer platanoides)
- Field maple (Acer campestre)
- Silver maple (Acer saccharinum)
Control
Tar spot does not affect the tree; control is not necessary.
Prevention
Plant less susceptible species, provide good growing conditions and clean up fallen leaves.
