SCIMAT / SCIENCE PHOTO LIBRARY SCIMAT / SCIENCE PHOTO LIBRARY
Norway maple leaf affected by a fungal disease called tar spot of maple, caused by Rhytisma acerinum. It is one of the least damaging ailments of the host. Related Rhytisma punctatum is generally distributed in the northern parts of North America. R. acerinum is sensitive to sulfur dioxide, a common pollutant, and for this reason, the disease seldom occurs in urban or industrial areas and is, actually, an indicator of an atmosphere free of the pollutant.
Model release not required. Property release not required.