lot of maple leaves affected by the pathogen rhytisma acerinum

acerinum adverse affected arrowshaped ascomycete autumn background biotrophic black close dampness daylight deciduous detail disease ecology effect environment europe flora foliage forest form fungus green habitat infected leaves lot maple natural nature october outdoors parasite park pathogen patterned plant plants points rhytisma seasons september shadow shady spot spots tar texture tree twigs veins widespread