Tar spot (Rhytisma acerinum)

The microscopic image shows an infected leaf with sclerotia. A consequence of monoculture.

Just like buildup of mold on pine needles and on the leaves of the willow, an ascomycete (Rhytisma) is the cause of tar spot. From late summer to autumn, round black mold deposits are growing on the leaves of several species of maple, which overwinter on the ground after the falling of the leaves. In spring distribution