BLACK SPOTS and PATHOGENS
In biology, a pathogen (Greek: πάθος, pathos "suffering", "passion" and -γενής, -genēs "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. [Wiki].
BLACK SPOTS : Rhytisma acerinum
Also called tar spots.
As is typical, this has been seen on sycamore trees on the upper Leven. See index.asp?pageid=732404
Wiki explains : Rhytisma acerinum is a plant pathogen that commonly affects sycamores and maples in late summer and autumn, causing tar spot. Tar spot does not usually have an adverse effect on the trees' long-term health. It is an Ascomycete fungus that locally infects the leaves of trees and is a biotrophic parasite.The disease is cosmetic and is therefore usually controlled only with sanitation methods.
When the spots appear they develop into brown-black lesions, retaining the yellow border. The lesions continue to grow, and by the end of summer form leaf spots that look like tar.
Black spots on sycamore leaves along the upper Leven in August.