181. Speckled Tarspot

The Tarspots are a group of fungi that infect leaves.  This one (Rhytisma punctatum) is a common, but relatively benign,  fungus that infects Bigleaf Maple.  It is most notable in the fall when the leaves of Bigleaf Maple start to fall.  At this time of year one can clearly see the black, tarry areas where the fungus sporulates.  The fungus protects the chlorophyll in the leaf from the usual breakdown by bacteria that an autumn leaf experiences.  This  leaves a green spot in the infected area while the rest of the leaf turns yellow.   The result is interesting and sometimes attractive patterns on the carpet of maple leaves on the forest floor.  Today was the first day I noticed significant numbers of Bigleaf Maple leaves on the ground  - another sure sign that summer is truly over.